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Old 12-28-2010, 04:25 PM   #1
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Default 1991 f150 heater isn't working

the heater just stopped working. So we were going to take it in. but when we were going to go there it started back up working. they couldn't figure what it could be. now it isn't working again. you can't feel any air coming out when you have it for the windshield at times. My husband leaves it going to hope it will keep the windshield from getting a film of ice on it. But it really doesn't help much. we may still get some ice. Can you help me.
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Old 12-28-2010, 04:46 PM   #2
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there are a series of vacuum lines behind the dash that allocate where the air is to be bown upon your selection with the heater/ac ****. There are 3 vacuum bases I believe. If you hear ANY hissing behind the dash selector **** you have a leak there, and can use clear silicone to tighten the seal. If there is no hissing there listen around under the middle and right side of the dash for other "hissing/Leaking" sounds. Here is a pic of the unit under the dash

Click the image to open in full size.

Last edited by MONSTERPRE; 12-28-2010 at 04:48 PM. Reason: 3 vacuum bases. far left is for defrost, middle is for floor/vents, under the hood is for heat/econ
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Old 12-28-2010, 05:01 PM   #3
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if you are NOT getting any heat when selection HEAT check this line for cracks, and the connection to the vacuum door baffle operator.

Click the image to open in full size.
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Old 12-28-2010, 05:47 PM   #4
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I have had 2 different trucks recently that have had a pen fall down the vent and block the door from closing to allow for hot air. I used a hole saw drilled into to see the door was not closing, and was stuck. Then drilled another hole on the bottom to pull the pens out! Cover the holes back up, and all was good.
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Old 01-02-2011, 09:06 AM   #5
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yesterday we had to go some where 1/1/2011. the air was working so we got heat. could there be some, not good connection going on? could that be the problem. something could be loose.
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Old 01-02-2011, 09:06 AM
 
 
 
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