heater not working
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Senior User
Joined: Jul 2007
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From: Ohio
heater not working
ok guys i was on the way to work this morning and my truck wouldnt blow any warm air. fan is working and i know its not the thermostat. the other day i pulled my pcm to get the code for ordering my chip but idk how that would of affected the heater. any ideas?
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
You said the fan is working. Is there no air blowing out of any vent (including defrost)? Or is it just not heating/cooling the air that is coming out?
What year/engine and what cab (Regular, Super or Crew)?
What year/engine and what cab (Regular, Super or Crew)?
Postmaster
Joined: Apr 2006
Posts: 3,524
Likes: 2
From: CA Bay Area
Hard to give direct advise not knowing the truck model?
On my 99 the heater core has no valve and is hot year around. It is the mixer operated door that opens the air flow around the heater, or AC evaporator.
So most likely the mixer is not working.
On my 99 the heater core has no valve and is hot year around. It is the mixer operated door that opens the air flow around the heater, or AC evaporator.
So most likely the mixer is not working.
Lead Driver
Joined: Sep 2007
Posts: 8,180
Likes: 669
From: Scio, OR
All 99-07 (and possibly beyond) had the grey hose that comes out for the core shutoff valve. 99-04 Crew Cab trucks and the Excursion had the valve itself, while Regular and Super cab trucks had the hose going to a nipple on the core box that just acted like a plug. 05 and up all trucks and the Excursion have the valve.
I'm thinking he probably knocked that hose loose and the vacuum leak that is causing is causing his air direction doors to go to default, or otherwise not work right.
Edit: Just to be clear on the whole thing, in none of these cases was the core shutoff valve to control temperature. It is either open or closed, no in between. On all models, temperature is controlled by the blend door, which is operated by an electric motor. The core shutoff valve blocks coolant to the core when the heat control switch is in MAX A/C and OFF only. In all other positions the valve is open.
I'm thinking he probably knocked that hose loose and the vacuum leak that is causing is causing his air direction doors to go to default, or otherwise not work right.
Edit: Just to be clear on the whole thing, in none of these cases was the core shutoff valve to control temperature. It is either open or closed, no in between. On all models, temperature is controlled by the blend door, which is operated by an electric motor. The core shutoff valve blocks coolant to the core when the heat control switch is in MAX A/C and OFF only. In all other positions the valve is open.
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Senior User
Joined: Jul 2007
Posts: 287
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From: Ohio
i got an 02 super cab. and i turned it on in the morning just to help clear the windows. also i took my pcm back out and put my chip in today and now it is working fine. idk if something didnt reset right when i unhooked the batteries or what
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