What to do if your heat pump is blowing cold air. There are a few reasons your heat pump could be blowing cold air. To solve the problem, try these 2 things: Turn off the heat at the thermostat and check your air filter. If it’s dirty, change it! Make sure the thermostat is set to “AUTO”, not “ON”. When set to “ON” the fan will ...If you have a wire in the R terminal and a wire in the Rc terminal, the jumper selector switch must be in the "2 Wire" position. Check your wiring. If you have a heat pump, you will not use a wire in the W terminal. Move the W wire to the W2 or Aux terminal. (W controls your first stage of heating for Gas/Oil/Electric systems.Central air conditioning is nice to have if your living space is sizable. For many consumers, though, window units suffice. Here are 10 compact, affordable units that beat the heat...Edenpure heater troubleshooting guide outlined the solutions to the heater's problems, including it won't turn on, won't turn off, keep shutting off, the fan not working, and the heater has no power. The other troubles are temperature issues, i.e. heater is not heating or overheating, heater's loud fan, heater blowing cold air, and heater beepsThe heating system is the biggest thing that I don't like about my 3. I HATE that it blows cold air after reaching the set temp vs lowering to a slow speed of hot air. The solution I use is to leave it on HI but have it set to 1. That usually is enough to keep the temps inside nice without the hot air cold air flip flop that it does.An oscillating fan rotates from side to side while blowing cold air out. Because of this movement, it is more effective than a stationary fan. While a stationary fan can only push ...1. Heat Pump Is in Defrost Mode. 2. Dirty Air Filters. 3. Incorrect Thermostat Setting. 4. Refrigerant Leakage. 5. The Air Feels Cold Due to Temperature Difference. …The heater core could be cloged. Take the hoses off the heater connections on the firewall, and try running some water through it. Also check the coolant level, if it is low the heater won't work worth anything. thats what happened with my 99 the gm dex cool antifreeze jelled up on mine and plugged up the heater core.Oct 22, 2023 · If your electric heater is blowing cold air, one of the first things you should check is the circuit breaker. A tripped breaker can cut power to the heating unit, causing it to blow cold air instead of warm air. The circuit breaker is a safety device designed to protect your electrical system from overload. If you have a furnace not blowing hot air, there could be many things causing the problem, but one of the more common reasons your furnace may be blowing cold air is set to “on” instead of set to “auto”. In this case, the fan will run constantly, even when the furnace isn’t heating. Simply re-setting the thermostat to auto should ...If it is set to cool or on constant fan, it will blow cool or cold air. Correct the settings. If that doesn’t fix the problem, don’t hesitate to call a professional. Keep in mind that air from a heat pump register may not be as toasty warm as air from a gas furnace register.At this time I still feel cool air on the driver side while I can feel heat on the passenger side. At this time: 1) The Mode motor (79140-SDA-A01) moves air where directed, so that doesn't seem like a cause. 2) The blower works, so I do not suspect the power transistor or the blower motor are the problem. 3) The SE trim level did not have …Heater takes a long time to blow hot air. Since the heating system in Escape relies on the hot coolant from the engine to heat the interior, the heater will blow cold air until the engine reaches its normal operating temperature. But if the weather is too cold, the engine may never reach its optimal operating temperature with a stuck open ...Thermostat Issues. The thermostat sends signals to your furnace to turn on …Jul 22, 2023 · Reason #2: The Air Filter Is Dirty. This is one of the most common reasons a gas furnace will blow cold air and won’t shut off. Air filters get dirty and have to be replaced or cleaned on a regular basis. Your furnace has a safety switch, called a high limit switch, that opens and turns the burner off to prevent overheating or heat exchanger ... Heater takes a long time to blow hot air. Since the heating system in Equinox relies on the hot coolant from the engine to heat the interior, the heater will blow cold air until the engine reaches its normal operating temperature. But if the weather is too cold, the engine may never reach its optimal operating temperature with a stuck open ...Malfunctioning Thermostat. A malfunctioning thermostat is one of the common culprits when your HVAC system blows cold air instead of heat. The …Without the heating, the blower will just blow out cold air. You need to check if your gas pilot light has gone out. To check it, just locate the pilot and see if it won’t light or if it won’t stay lit. If this is the case, the cold air coming from a furnace is due to a faulty pilot light. Solution: Simple in theory.Common Reasons For Furnaces Blowing Cold Air: Your Furnace Isn’t Warmed Up Yet. Your Thermostat is Set Incorrectly. The Furnace Filter is Dirty. Your …If your furnace only blows cold air after you’ve turned on the heat, start your troubleshooting at the thermostat. Double-check that it’s set to “Heat” and “Auto,” not …If it is set to cool or on constant fan, it will blow cool or cold air. Correct the settings. If that doesn’t fix the problem, don’t hesitate to call a professional. Keep in mind that air from a heat pump register may not be as toasty warm as air from a gas furnace register.If you have a furnace not blowing hot air, there could be many things causing the problem, but one of the more common reasons your furnace may be blowing cold air is set to “on” instead of set to “auto”. In this case, the fan will run constantly, even when the furnace isn’t heating. Simply re-setting the thermostat to auto should ...Cold air return vents work by allowing cool air to be suctioned into a furnace or heating/air conditioning system. The cool air is then heated or cooled, depending on the system se...My wife just had her heat fixed, she had the same problem no heat just blowing cold air, turned out that the car had 2 issues. 1 the thermostat was stuck open so that was replaced and 2 there was a clog somewhere in the heating system which wasn't allowing the coil to heat up so they cleared that and everything is working great now.Find the procedure in a shop manual (at auto parts stores for about $20). But if your car heater blows cold air and you’ve checked both heater core hoses to make sure they’re hot, you likely have a bum blend door actuator. You can usually diagnose and fix the problem yourself in about an hour. A new door actuator costs less than $100.Clogged air filters could be causing cold air to blow out of your vents. A dirty air filter can block airflow over your furnace’s heat exchanger, which can cause it to overheat. Your furnace can then trip a …Why Is My Heater Blowing Cold Air? HVAC systems are intricate pieces of machinery. With so many parts, things often go wrong and need to be updated or …PIT5491 - Heater blowing cold air. I did a quick search for the PIT number, but there were no hits. Has anyone here had this issue? My truck has had this issue fixed twice now. The first time the "temperature valve" actuator arm was broken, so the valve was replaced. I was originally told that the valve was broken from the factory.1) Turn on ignition, but do not start the car (foot off brake, press start twice - dashboard lights should be on) 2) Set both temp controls all the way up. 3) Hit "auto" on the climate control. 4) Turn fan control all the way down. 5) Press and hold gas pedal down for about 10 seconds.Why Is Your Mercedes-Benz Car Heater Blowing Cold Air? · Low Coolant Level. One of the most common causes of a Mercedes-Benz car heater blowing cold air is a ...If your heater is blowing cold air, it can be a frustrating and in cold enough temperatures, potentially dangerous situation. Dealing with a broken heater in the winter can be stressful, but luckily there are steps you can take to stay warm. Keep your curtains and blinds closed to retain heat, and use extra blankets and layers to stay warm.16 Sept 2020 ... The heater core itself can go bad. Over time, they are known to clog and fail. If you have a heater core that clogged, it's not going to be able ...The Electrical Panel. Now you are starting to get into the territory where you are definitely going to want some outside help, especially when your heating unit is blowing cold air. If your …The heating system can run into several problems described below, resulting in the car heater blowing cold air. 10 Reasons Why Your Car Might Be Blowing Cold Air Faulty Thermostat. The thermostat regulates the flow of the coolant in the engine. It does so by opening or closing its valves when the engine’s temperature reaches a specific level.Heater takes a long time to blow hot air. Since the heating system in Town and Country relies on the hot coolant from the engine to heat the interior, the heater will blow cold air until the engine reaches its normal operating temperature. But if the weather is too cold, the engine may never reach its optimal operating temperature with a stuck ...Nov 14, 2023 · Having the fan on continuously can blow cold air into your living spaces in between heating cycles. Pilot Light Is Out. If you have an older gas furnace model that still has a traditional pilot light, a common issue leading to a furnace blowing cold air is a pilot light that has gone out. If you’re comfortable doing so, relight the pilot ... When your car heater consistently blows cold air during idle, it suggests a problem with the cooling system. Insufficient coolant flow due to a malfunctioning radiator fan, a clogged radiator, or a faulty water pump can disrupt heat transfer. Ask a professional to inspect your cooling system and rectify the underlying issue. 3.Central air conditioning is nice to have if your living space is sizable. For many consumers, though, window units suffice. Here are 10 compact, affordable units that beat the heat...Nov 22, 2021 · After changing the filter and waiting a few minutes, check if your heating system is blowing warm air, and if it’s not, you’ll likely need to look for other causes. 2. Malfunctioning or Improperly-Set Thermostat. Another common culprit behind a heating system blowing cold air is a malfunctioning or improperly-set thermostat. 71 posts · Joined 2010. #1 · Feb 23, 2010. I have a 2003 6.0 f350. In the winter (I live in Michigan) my heater does not blow hot air. I would call it luke warm at best. The faster that I go the warmer it is. IE: its warmer at 75mph than at a light at idle. Someone recommended that I install a cover over the radiator on the grill for winter.If the heater is still blowing cold air, it could be because of other issues. #7. Heater Control Issues. Sometimes the car’s heating system works perfectly, but it still blows cold air. It can be because of heater control issues. The heater control valve works to regulate the flow of hot coolant inside the heater core. It can get clogged with ...6 posts · Joined 2012. #1 · Dec 10, 2012. While I was visiting North Florida last week, the heater on my 2008 Armada started blowing cold air. The controls work fine, the AC works fine, but the heater will not get warm. I looked in other forums, and it looked like the problem is more than likely the heater (water) control valve (HCV).3 posts · Joined 2019. #1 · Oct 8, 2019. My girlfriend has a 2015 Ford Escape SE 1.6 and her heater blows only cold air. I havent popped the hood yet so I have no specific info at the moment. I'm hoping y'all can throw some ford specific info at me. I'm not a mechanic by trade, but I do my own maintenance and parts replacement.Heater takes a long time to blow hot air. Since the heating system in Accord relies on the hot coolant from the engine to heat the interior, the heater will blow cold air until the engine reaches its normal operating temperature. But if the weather is too cold, the engine may never reach its optimal operating temperature with a stuck open ...Central NY. With you truck warmed up both heater hoses should be hot... not warm, hot. If only one is or neither then you may have a plugged core. If both are hot then there is flow through the core and its most likely the blend door not opening due to either a bad actuator motor or a broken blend door tube.PIT5491 - Heater blowing cold air. I did a quick search for the PIT number, but there were no hits. Has anyone here had this issue? My truck has had this issue fixed twice now. The first time the "temperature valve" actuator arm was broken, so the valve was replaced. I was originally told that the valve was broken from the factory.A truck heater blowing cold air could be due to several reasons, such as a malfunctioning thermostat, low coolant levels, air pockets in the cooling system, a faulty heater core, or a blocked heater valve. Professional inspection and troubleshooting are recommended to determine the specific cause and resolve the issue. Why is my truck’s …20 Oct 2023 ... If you gauge is in the normal middle zone and the heat set to dash vents still blows cold I would suspect an issue with the temp control valve.If your furnace is blowing cold air in your home, this is a sign of an issue with the flame detector, gas supply, air filter, pilot light, or condensate lines. Many of these …20 Oct 2023 ... If you gauge is in the normal middle zone and the heat set to dash vents still blows cold I would suspect an issue with the temp control valve.24 Sept 2011 ... 2 Answers 2 · Bad thermostat · Pilot light out (if a gas furnace with a pilot light) · Heating element out (if electrical furnace) · It... Once the engine is warm, if the thermostat can't signal that, heat won't be provided to the heater core because coolant won't be sent there. Cold air will blow. To get your heater working again, a new thermostat must be installed. Coolant Level Is Low. Most people think that overheating prevention is the sole purpose of coolant. Help. Heater blowing cold air. 2018 F150 V8. With 89k miles factor coolant is a little discolored but extremely clean. last month I posted about my random coolant leak now that it’s getting colder I tried running the heater fan works. Blender doors work. But no heat blows cool air. So I check the hot/cold blender turns fine.Check that the heater fan is blowing. If it’s only blowing on high speed, the blower motor resistor might be faulty or a fuse might be blown. Clean off the radiator. If it’s plugged …Nov 22, 2021 · After changing the filter and waiting a few minutes, check if your heating system is blowing warm air, and if it’s not, you’ll likely need to look for other causes. 2. Malfunctioning or Improperly-Set Thermostat. Another common culprit behind a heating system blowing cold air is a malfunctioning or improperly-set thermostat. Audi A4 heater core hoses. There are a few reasons why a car heater is blowing cold air even after the engine reached its optimal operating temperature. These reasons include: Faulty heater core. Not enough coolant. Faulty thermostat. Bubbles in the cooling system. Faulty heater controls.Feb 12, 2019 · Solution: Set the heater to its maximum setting, remove the coolant tank cap and fill it to the proper level. Start the engine with cap still open and let the engine idle for a few minutes. If the coolant level should drop as the thermostat opens, top it up as necessary. This should bleed off the air bubble. Nov 22, 2021 · The furnace can blow cold air occasionally for various reasons, ranging from air leaks to short cycling and everything in between. The following are the seven most common causes and how to fix them. 1. Thermostat Issues. The first place to check when your furnace is blowing cold air is the thermostat. Once the engine is warm, if the thermostat can't signal that, heat won't be provided to the heater core because coolant won't be sent there. Cold air will blow. To get your heater working again, a new thermostat must be installed. Coolant Level Is Low. Most people think that overheating prevention is the sole purpose of coolant. Check Furnace Air Filter. A second reason that your heater might be blowing cold air instead of warm air is due to a faulty furnace air filter. Furnaces fit with a clogged filter or dirty air filter can cause the heater to work overtime in order to compensate for the lack of indoor airflow and waste energy. To fix this issue, clean or replace ...Solution: Set the heater to its maximum setting, remove the coolant tank cap and fill it to the proper level. Start the engine with cap still open and let the engine idle for a few minutes. If the coolant level should drop as the thermostat opens, top it up as necessary. This should bleed off the air bubble.Locate the heater hoses on the firewall and determine which is flowing in and which is flowing out. Remove the hoses and attach a couple short lengths of surrogate hose. Run the garden hose through the out/return line for a couple minutes. Hook everything back up and test the vent heat.Driver's side heat will set me on fire (I'm assuming it's probably trying to compensate for the cabin temp difference). What's strange is that I've turned the passenger side heat up to "HI" and it seems like the vent gets shut closed, but as I bring the temp back down into the 70's, the vent will open and start to blow cold air. Once the engine is warm, if the thermostat can't signal that, heat won't be provided to the heater core because coolant won't be sent there. Cold air will blow. To get your heater working again, a new thermostat must be installed. Coolant Level Is Low. Most people think that overheating prevention is the sole purpose of coolant. Aug 12, 2022 · If you have a wire in the R terminal and a wire in the Rc terminal, the jumper selector switch must be in the "2 Wire" position. Check your wiring. If you have a heat pump, you will not use a wire in the W terminal. Move the W wire to the W2 or Aux terminal. (W controls your first stage of heating for Gas/Oil/Electric systems. 2016 F150 EcoBoost Heater blowing old cool air. I have a 2016 F150 FX4 and the heater is only blowing cool air. The air from the vents all work great but just the air is not getting hot. I started with the cooling fans being stuck on high anytime the truck was running with the AC on and/or off and then shortly after I lost cold air, now the ...When the thermostat isn't working correctly, it can't signal to the car that the engine is warm. As a result, the coolant won't be sent over to provide heat to ...If your fan is running all day, it eventually starts to feel like cold air is blowing, whether or not you have the heat on. You can check the fan mode by going to Ecobee’s Comfort Settings. Go to Main Menu > Comfort Settings. From here, you have the option to set the fan to “Auto” or “On” in both heat and cool mode.May 3, 2016 · Arlind86, Thanks for posting these instructions. I have a 2008 S550 that I recently bought, this was the first time I drove it in the winter cold weather, the heat was always working but after driving to the store I parked the car in the parking lot and the heat suddenly stop working, it was only blowing cold air. Car Heater Blowing Cold Due to Cooling System Issue. The four main cooling system problems that can cause a heater to blow cold air are: Stuck thermostat. Air in the cooling system. Plugged heater core. Coolant not flowing through the heater core. It's a little more complicated than that in practice, but these are the most common heater …Mar 1, 2014 · Heater blows cold air. My wife has a 2005 Impala LS (3.8L). She continues to tell me her car never warms up anymore. Finally, we were driving to a restaurant last night and I finally noticed the car is just blowing cool air when the heat is on. The cool air is coming from both sides of the car (driver/passenger). Audi A4 heater core hoses. There are a few reasons why a car heater is blowing cold air even after the engine reached its optimal operating temperature. These reasons include: Faulty heater core. Not enough coolant. Faulty thermostat. Bubbles in the cooling system. Faulty heater controls.Your heater has to first collect and compress the air in your home, then heat it and expel the cold air. Heating systems work by heat exchange, which means that …2009 - 2014 Ford F150 - Heat on but blowing cold air - I have the Microsoft sync with the Sony stereo and navigation. Well, it’s starting to get cold and my heater is working very intermittently. Majority of the time it blows cold air, but occasionally it will blow hot air or just so so heat.Furnace blowing cold air. 03-12-2021, 11:55 AM. Hey all....New to the group. Have a 2020 Grand Design Momentum 395. Furnace was working yesterday and we moved from one spot to another. I had shut off the propane during travel and when we set up in our new spot, once the temp went down, no heat. Checked the valves, open.Solved - Heater blowing cold - coolant leak ... So, plastic air boxes back on and I believe that’s job done. Total cost for this fix, apart from time was £54 GBP (£32 for new hose pipe; £17 for 4 litres of Preston yellow concentrated coolant and £5 for 5 litres of De-ionised water to mix with the Preston concentrated coolant).20 Oct 2023 ... If you gauge is in the normal middle zone and the heat set to dash vents still blows cold I would suspect an issue with the temp control valve.14 Mar 2022 ... Dirt Build-up – if your filter gets clogged for any reason, the heater will blow cold air. A dirty filter prevents the air from passing over the ...28 Nov 2018 ... Car Heater Blowing Cold Air? Here's Why! · There isn't enough coolant in the engine · There is a problem with your heater core · Your&n...If the heater is still blowing cold air, it could be because of other issues. #7. Heater Control Issues. Sometimes the car’s heating system works perfectly, but it still blows cold air. It can be because of heater control issues. The heater control valve works to regulate the flow of hot coolant inside the heater core. It can get clogged with ...3 Jan 2023 ... So your cabin heat comes from the hot coolant passing through a small radiator(aka “heater core”) inside the dash. The fan blows air through ...Help. Heater blowing cold air. 2018 F150 V8. With 89k miles factor coolant is a little discolored but extremely clean. last month I posted about my random coolant leak now that it’s getting colder I tried running the heater fan works. Blender doors work. But no heat blows cool air. So I check the hot/cold blender turns fine.But now the heater only blows cold air. The fan is working OK at all selections. I tried venting air out of radiator system by removing the radiator cap, running the engine for five minutes until it was warm but that was no help. The upper hose to the heater core gets hot but lower one doesn't so it seems that something is preventing the hot ...Dec 16, 2022 · It’s possible a gas furnace won’t heat because it’s not getting a proper gas supply. This is another scenario where the furnace will blow cold air and then shut down. Double-check the shut-off valves to make sure they’re open. If there’s still no gas reaching the furnace, it indicates an issue somewhere in that system. The core, a type of heat exchanger, gets its heat from liquid engine coolant that circulates through it by means of heater hoses. Air driven by the blower picks up the heat on its way into the ...29 Dec 2019 ... To protect the outdoor coils from freezing up in the winter, heat pumps go through a defrosting period every hour or so in which they are truly ...Usually, if the thermostat is stuck open, you get LESS heat while driving than while stationary, due to more cold air being forced through the radiator while driving. If the thermostat is stuck closed, the engine overheats. Your problem sounds more like low coolant level - i.e., the water pump is moving a lot of air mixed with the coolant.Dec 21, 2020 · The air your furnace heats has to travel through cold ductwork, where it can lose a lot of heat along the way. Once your ductwork has warmed up, not as much heat will be transferred to it as air blows through it. At that point, the air coming out of your vents should start to feel warm. 2. Your thermostat is set to the incorrect setting.
PIT5491 - Heater blowing cold air. I did a quick search for the PIT number, but there were no hits. Has anyone here had this issue? My truck has had this issue fixed twice now. The first time the "temperature valve" actuator arm was broken, so the valve was replaced. I was originally told that the valve was broken from the factory.. White yams
If you have a furnace not blowing hot air, there could be many things causing the problem, but one of the more common reasons your furnace may be blowing cold air is set to “on” instead of set to “auto”. In this case, the fan will run constantly, even when the furnace isn’t heating. Simply re-setting the thermostat to auto should ...If it is set to cool or on constant fan, it will blow cool or cold air. Correct the settings. If that doesn’t fix the problem, don’t hesitate to call a professional. Keep in mind that air from a heat pump register may not be as toasty warm as air from a gas furnace register.1. Clogged Air Filters. Clogged air filters are one of the reasons why the Modine garage heater won’t ignite. Over time, dirt and dust particles accumulate in the filters and create a blockage that causes a disruption in the path of the warm air. Clean the air filters properly to get rid of all the dirt and dust particles.Check Furnace Air Filter. A second reason that your heater might be blowing cold air instead of warm air is due to a faulty furnace air filter. Furnaces fit with a clogged filter or dirty air filter can cause the heater to work overtime in order to compensate for the lack of indoor airflow and waste energy. To fix this issue, clean or replace ...6.7 Cummins Heater Blowing Cold Air . If you own a 6.7 Cummins and your heater is blowing cold air, there are a few things that could be the culprit. First, check to see if the engine coolant level is low. If it is, add more coolant until it reaches the full line on the reservoir. Next, check the thermostat to see if it’s stuck in the closed ...90. First thing to check is if the thermostat is stuck open. If so, the coolant will never heat up to provide heat. Honestly, thermostats are cheap, if you are taking it out to check it would be wise to just replace it. Good time for a coolant flush and replace. If that doesn't fix it, and the coolant level is good, you could be looking at a ...Jan 8, 2014 · 1) Turn on ignition, but do not start the car (foot off brake, press start twice - dashboard lights should be on) 2) Set both temp controls all the way up. 3) Hit "auto" on the climate control. 4) Turn fan control all the way down. 5) Press and hold gas pedal down for about 10 seconds. Dec 16, 2022 · It’s possible a gas furnace won’t heat because it’s not getting a proper gas supply. This is another scenario where the furnace will blow cold air and then shut down. Double-check the shut-off valves to make sure they’re open. If there’s still no gas reaching the furnace, it indicates an issue somewhere in that system. Jan 17, 2016 · The core, a type of heat exchanger, gets its heat from liquid engine coolant that circulates through it by means of heater hoses. Air driven by the blower picks up the heat on its way into the ... What travelers should know about new temperature limits for air conditioning and heat throughout Europe. If you know me, you know that my love for air conditioning knows no limits....The heating system is the biggest thing that I don't like about my 3. I HATE that it blows cold air after reaching the set temp vs lowering to a slow speed of hot air. The solution I use is to leave it on HI but have it set to 1. That usually is enough to keep the temps inside nice without the hot air cold air flip flop that it does.Take a look at the temperature setting on the thermostat and the temperature inside the house. Digital thermostats should display both values. When the thermostat’s setpoint is 74f degrees and the thermostat reads 74f or above, and the blower is still operating, the faulty sensor could be the cause.Car Heater Not Working? Common Cooling Issues Are to Blame! · The thermostat may be stuck, causing the coolant to stay pooled in one area rather than ...Clogged air filters could be causing cold air to blow out of your vents. A dirty air filter can block airflow over your furnace’s heat exchanger, which can cause it to overheat. Your furnace can then trip a …After a bit and timing varies the heat will get cooler or go straight to dead cold. After a few minutes to 20-30 minutes it’ll come back and get warm or hot. Sometimes if I switch it from hot to cold, or change it from blowing out the top, to feet and back it seems to help *sometimes* could be a coincidence. My coolant level is fine.Mar 1, 2014 · Heater blows cold air. My wife has a 2005 Impala LS (3.8L). She continues to tell me her car never warms up anymore. Finally, we were driving to a restaurant last night and I finally noticed the car is just blowing cool air when the heat is on. The cool air is coming from both sides of the car (driver/passenger). If your electric heater is blowing cold air, one of the first things you should check is the circuit breaker. A tripped breaker can cut power to the heating unit, causing it to blow cold air instead of warm air. The circuit breaker is a safety device designed to protect your electrical system from overload.353 posts · Joined 2009. #1 · Apr 26, 2011. Well, as stated above my heater won't blow anything but cold air and only on the window defroster and feet, I can change the setting to the front vents but it never switches. There were no symptoms of the heat going. I shut the truck off and it was working, then a few hours later i started it and ... Once the engine is warm, if the thermostat can't signal that, heat won't be provided to the heater core because coolant won't be sent there. Cold air will blow. To get your heater working again, a new thermostat must be installed. Coolant Level Is Low. Most people think that overheating prevention is the sole purpose of coolant. .