Question about 1990 GMC C1500

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My heater runs cold even when the engine is warmed up.

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Sounds like either thermostat stuck open or your heater core is clogged...

Posted on Oct 15, 2010

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6ya6ya
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Posted on Jan 02, 2017

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  • 141 Answers

SOURCE: heater on ford 2003 ford pick up blows cold air

on the evap box there is a control mtr that switches the hot cold door. these mtrs are prone to failure. the other problem that i have seen is that the door breakes in side the evap box and that means removing the box to replace the door . if i remeber correctly you may have to slide the dash back to gain assces to the control mtr to test it good luck

Posted on Dec 22, 2008

  • 84 Answers

SOURCE: 2001 Kia Rio running too cold

First thing to test would be the thermostat. If this is stuck open the engine would never reach correct temperature.

Posted on Dec 22, 2008

  • 1 Answer

SOURCE: Heater blows cold air when idle

Sounds like you may have a partially plugged heater core. You could flush this out separately, from flushing radiator & engine block. Diconnect heater hoses going to your heater core and clamp off, so not to loose coolant from engine. Now hook up separate hose to one side of heater core pipe and flush out with typical garden hose. Repeat procedure on both heater core inlets. Reconnect original heater hoses and test difference. You may have to add an additional litre of antifreeze. If this don't work i suggest changing heater core. Good luck.........Ron.

Posted on Jan 03, 2009

  • 1 Answer

SOURCE: Heater blowing cold on 2005 Nissan Xterra

I live in Alaska and have had the same problem i just added more coolent to the radiator and it warmed up i installed a block heater and i leaked a bit and the coolent level got low and i would have no heat. I tryed to fill just the coolent resivoir and that dident work so i filled the radiator pumb full and that worked!! Hope this helps.

Posted on Jan 18, 2009

bozcro
  • 867 Answers

SOURCE: 2000 Buick LeSabre heater only blows cold

the climate control thermostat is not opening the valve to let the warm coolant in

Posted on Nov 29, 2009

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1 Answer

2009 pontiac g6 heater blows cold


Have you checked your actuator ? Internal mechanical / electronic flap that allows warm coolant from engine to run inside your car into heater core.

With vehicle at operating temperature, touch both heater hose inside engine compartment by firewall. They should both be warm/hot if actuator is good. If one is cold, bad actuator or clogged heater core.

Dec 07, 2016 | Pontiac Cars & Trucks

1 Answer

Heater not blowing hot air


Hi Chris, sounds like your thermostat may be worn and not closing all the way which would cause your engine to run cool at times. If you have a temp gage it should tell you if the engine is actually warming up or not. If not I would replace the thermostat.

Mar 18, 2014 | Ford Mustang Cars & Trucks

1 Answer

Heaters running cold at 90 degrees


If the engine is running at a normal temperature I would suspect the thermostat.
Normally from a cold start the coolant should only circulate through the bypass hose, the heater matrix, and back through the engine, As the engine warms up and the thermostat begins to open the coolant is directed through the main radiator - at this point you will be able to feel the upper and lower radiator hoses warming up.
If the thermostat is faulty and permanently open you will be able to feel the upper and lower radiator hoses warming up very soon after starting the engine and at the same time as you feel the heater hoses begin to warm. This causes most of the heat to be radiated away and so the heater will never warm up.
Unfortunately the thermostat is hidden underneath the water pump on a passat and requires the cooling system to be drained before it can be changed. It may also require the power steering pump to be removed to get access to the thermostat cover.

Feb 01, 2014 | 2001 Volkswagen Passat

1 Answer

Heater not warming up


Most likely the thermostat broke. I expect that you have an older Hyundai and never had the anti-freeze changed. When the engine is cold the thermostat is closed which causes the engine to warm up more quickly. A warm engine runs more efficiently (less gas) and more smoothly. When the engine temp reaches a certain temp the thermostat opens and then allows the hot engine coolant to run through the lines to the heater core. The heater blows air over the heater core which produces the warm air that warms up the cabin. Thermostats used to be cheap and easy to change. I would suggest a web search for how to replace the thermostat. Something like 'hyundai accent 2002 replace thermostat".

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No heat in 2001 chevy nblazer


If the thermostat is not working the engine will not warm up. So the temp gauge should show cold after running the engine for 10 or 15 min.
If the engine is warming up but the heater hoses are not warm, you could have air in the cooling system.

Sep 11, 2012 | 2001 Chevrolet Blazer

2 Answers

2002 grand prix, will not blow hot air, engine heats up fine and cooling system checks ok.


With the engine warmed up feel the heater lines going into the firewall. You will probably find that one is very hot and the other only look warm or even cold. If this is the case the heater core needs to be flushed. With the engine cold remove the hoses at a convenient location and back flush the heater core. Reconnect the lines and warm the engine back up with the heat on.

Jan 11, 2010 | 2002 Pontiac Grand Prix

1 Answer

No heat air is blowing cold


First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced.
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is worm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest to flush the heater core.

Oct 22, 2009 | 1998 Ford Taurus

1 Answer

MY 1998 FOR TARUS HEATER WILL NOT WORK.WAS DRIVING


It is most probably the problem with blend door or blend door actuator. But just in case I would suggest to follow the entire procedure:

First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is warm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest flushing the heater core.

Oct 17, 2009 | 1998 Ford Taurus

1 Answer

Heater not working


First you have to identify what causes the problem.
To do this you have to:
1) When engine is cold check the level of coolant. If it is low fill it up.
2) Start engine and check if engine reaches regular temperature. If your engine is not heated enough it means your thermostat does not work properly and should be replaced.
3) If engine temperature is normal, then check the temperature of pipes that go to/from heater core. These pipes are located up the fire wall (easier access is from the passenger side). If pipe/pipes are cold (even engine is warm) it means you heater core is plugged and should be flushed. Keep in mind, flushing the whole cooling system is different from flushing heater core.
4) If pipe/pipes are hot/warm, turn off the fan, switch controller to the hot position, wait for 3-4 minutes and turn on the fan. Note if the cold air blows first or warm air blows first but it cools down in 5-10 seconds. If the air blows cold than it is most probably the problem with blend door or blend door actuator.
5) If air blows warm first and then cools down, then while running engine and remaining the transmission in PARKING position, press on the gas pedal until your engine reaches 3,000 RPM. Check if your heater blows warm/hot air. If it does, then your water pump does not work properly and should be replaced. If the air still cold, I would suggest flushing the heater core.

Oct 17, 2009 | 1998 Ford Taurus

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