Heater Problems
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New User
Joined: Jan 2011
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From: Fort Worth, TX
Heater Problems
Hey guys i have a '99 F150 4.2 5 speed, my problem is, my heating isn't working. My A/C works fine, my blower motor does too, i changed my heater core about a year ago. I turn my truck on wait for it to warm up and once my gauge reads normal temp, i turn my control **** to the warm position but the air blows cold with just a very small hint of heat. I looked it up in my Chilton book and they said to check my hoses that go to the firewall/heater core. They say that both hoses should be hot and if one isn't to check it. i did that and the one on the left side(facing the truck) is barely warm. what could be my problem? heater core? my friend from Autozone said something about a vaccum control somewhere in the engine compartment but i don't know where it is, could that be a problem? Or would the flapper door be stuck? Any help will be helpful.
-Hector
-Hector
Fleet Owner
Joined: Aug 2010
Posts: 21,253
Likes: 1,656
From: Reynoldsburg, Ohio
Your flapper door or blend door would seem to be not working properly. Assuming you've checked for proper coolant flow through the core that's about the only other thing that'd give these symptoms.
It could anything from the blend door being unable to pivot which is somewhat common, the drive motor or temperature control also having failed. Perhaps call for A/C, turn the temp control to full "warm" and see if that has any effect---most likely it won't.
Next step would be removing the drive motor and watch its motion while still connected and moving the temp control. If it moves with the temp control its your blend door.
Those are available separately but Ford wants to sell you the entire heater/evaporator box for quite a bit---$200 or more IIRC. Its the same work changing the blend door as the heater case so why not save yourself considerable money. I found my parts on eBay but places like RockAuto.com or other retail outlets probably have them too.
Its not as bad a job changing these as you'd think---there are a few posts under my user name on this site that you might find helpful.
HTH
It could anything from the blend door being unable to pivot which is somewhat common, the drive motor or temperature control also having failed. Perhaps call for A/C, turn the temp control to full "warm" and see if that has any effect---most likely it won't.
Next step would be removing the drive motor and watch its motion while still connected and moving the temp control. If it moves with the temp control its your blend door.
Those are available separately but Ford wants to sell you the entire heater/evaporator box for quite a bit---$200 or more IIRC. Its the same work changing the blend door as the heater case so why not save yourself considerable money. I found my parts on eBay but places like RockAuto.com or other retail outlets probably have them too.
Its not as bad a job changing these as you'd think---there are a few posts under my user name on this site that you might find helpful.
HTH
New User
Joined: Feb 2016
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I have done everything that I read on here and I'm still getting air and no heat. The fan works and the door plus the heater core and thermostat is brand new so I really don't know what else to do any suggestions oh and I have a 1999 f150
Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
Did you check the temperature of the heater coolant lines? No hot coolant circulating through the core = No Heat.
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Hotshot
Joined: Jan 2004
Posts: 19,762
Likes: 1,079
From: St Louis
Then you're not geting circulation.
Therefore, your possibilities, assuming you have verified the engine is actually at operating temp - check thermostat housing with an IR thermometer if in doubt - are as follows:
1. Low coolant.
2. Air bubble in heater loop.
3. Restriction in heater loop.
4. Worn out or failed water pump.
Good luck.
Therefore, your possibilities, assuming you have verified the engine is actually at operating temp - check thermostat housing with an IR thermometer if in doubt - are as follows:
1. Low coolant.
2. Air bubble in heater loop.
3. Restriction in heater loop.
4. Worn out or failed water pump.
Good luck.
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