Heater issues

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Feb 17, 2015 | 09:49 AM

johnstonmatt77

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Heater issues

I have a 1996 f150 and the heater isn't working right. The heat will come on, but only while I'm giving it gas. When I let off the gas, the heat will go cold. Could this be a vacuum problem and if so, where would it be at?

Feb 17, 2015 | 10:10 AM

broncoderek

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Probably just need to fill up your radiator making sure to rid it of air.

I just fill mine while it's running.

Other than that, a vacuum leak can affect the switching of the heat locations but I'm going with my first idea.

Feb 17, 2015 | 11:02 AM

aj88V

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From: NoVa

Quote:

Originally Posted by broncoderek

Good advice above.

Other than that,
1) was the heat working well recently, and then stopped working?
2) is the engine temperature gauge showing normal?
3) can you feel a difference when the cab temp selector is on hot vs. cold?

Feb 18, 2015 | 10:02 AM

johnstonmatt77

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Quote:

Originally Posted by aj88V

I'm the third owner of the truck and the heat only worked when j was giving it gas. However, a few days ago, the heat would stay on all the time regardless if I was giving it gas or not. But now it only work while I'm pressing the gas pedal. The temp gauge is normal and there is not that much difference when I switch from hot or cold.

Feb 18, 2015 | 02:36 PM

aj88V

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From: NoVa

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ontFlipMirrorIndents/> <w:OverrideTableStyleHps/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument> </xml><![endif]--> I would verify that the coolant system is full properly purged of air first. Giving it gas spins up the water pump, pushing fluid through the system faster, so if you've got an air pocket in the system, that might overcome it, giving you heat.

Note, when purging the air, I leave the radiator cap off and run the engine until she gets hot. You can see the air pop out of the water. Revving it up does help get the air out. Give it a touch of gas and you can see the water level drop as the pump kicks up, but the water will surge if you let the gas off too fast. Keep filling with water if you get a big burp of air. After the air is out, shut down the engine, fill it up with water, replace the radiator cap, and fill the coolant reservoir to the Hot line.

“Not much difference between Hot and Cold”:
Suspect either the seal on the door others have mentioned or the vacuum controls.

The vacuum controls in the Fords are a pain in the butt. Just like my 1972 LTD. Feel like I’ve gone back in time looking at it. Revving the engine usually drops the manifold pressure, making it worse, so probably not that. Ford uses a big old steel juice can as a vacuum reservoir. You can have problems with these systems if any of those lines are leaking or the vacuum dashpot actuators are leaking and you’re not getting good vacuum.
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