Fan and function problems
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From: SC
Fan and function problems
Summer is here and I decided to turn on the AC in the truck. I just bought the truck in the winter, and only tested the AC when I bought it. I have a couple of problems as of right now.
1. The AC only works on speeds 1 and 4. Nothing comes out on 2 or 3.
2. Sometimes, when I turn the air on so it will come out of the vents in th dash so it will hit me, it comes out of the defroster... I dont know why.
About the first one, when I turn the air from 4 back to 1, it makes a loud sound like the fan has gone bad. I am sure this is probably the case, I just dont know how to go about fixing it...
And the second one... your guess is as good as mine... im guessing some sort of bad diverter or something along those lines... Any help in this area is great to me, because I have never really had AC issues before. The truck is a 1996 F150 Single cab, XLT. Thanks in advance for all the help!
1. The AC only works on speeds 1 and 4. Nothing comes out on 2 or 3.
2. Sometimes, when I turn the air on so it will come out of the vents in th dash so it will hit me, it comes out of the defroster... I dont know why.
About the first one, when I turn the air from 4 back to 1, it makes a loud sound like the fan has gone bad. I am sure this is probably the case, I just dont know how to go about fixing it...
And the second one... your guess is as good as mine... im guessing some sort of bad diverter or something along those lines... Any help in this area is great to me, because I have never really had AC issues before. The truck is a 1996 F150 Single cab, XLT. Thanks in advance for all the help!
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From: SC
Okay i saw where it was written that the air coming out of the defroster could come from a vaccuum leak. Any more information on this for a 96 would be appreciated. And the question still stands for the fan.
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Joined: Jul 2005
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Yes this is a vacuum leak...
I am working on this myself. For "safety reasons" the defroster is where the selctor goes to when there is insufficiant vacuum or a leak. Use a vaccum gauge to test where your leak is. There is a vaccum reservoir in the fender behind the battery that is often at fault. There is a line through the firewall and then a line through a check valve (test it also) and then to the manifold. Unfortunately my leak is under the dashboard and I have not traced it yet...
Mountain Pass
Joined: Sep 2002
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For your fan problem. Locate the resistor bank in the air duct and pull it out. If you have an ohm meter, check resistance of resistors, probably need to replace it.
For the defrost issue, I doubt the vacuum canister has a leak or your truck would be running like crap because lots of emission controls and your brakes, rely on good vacuum. Find the damper motors that direct the air to defrost, feet and dash. Listen close under the dash and you may hear a hissing sound, locate it and fix the vacuum leak. You could also have a bad selector switch. Just have to track down where the leak is and resolve it. A shop manual would be a good idea to be able to see the schematic and parts involved in the vacuum controls for the heat and a/c.
For the defrost issue, I doubt the vacuum canister has a leak or your truck would be running like crap because lots of emission controls and your brakes, rely on good vacuum. Find the damper motors that direct the air to defrost, feet and dash. Listen close under the dash and you may hear a hissing sound, locate it and fix the vacuum leak. You could also have a bad selector switch. Just have to track down where the leak is and resolve it. A shop manual would be a good idea to be able to see the schematic and parts involved in the vacuum controls for the heat and a/c.
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Vacuum leak
The specific vacuum canister is only for the HVAC system. A leak in this would have precisely the same effect than a leak under the dash. It would cause only a very small performance degradation -- nearly unnoticeable (depending on the size of the leak of course).
I had the same "switching to defroster" problem. It was a faulty check valve by the cannister (a $2.99 part) and a small leak under the driver's side of the dash at a junction of six vacuum tubes.
I had the same "switching to defroster" problem. It was a faulty check valve by the cannister (a $2.99 part) and a small leak under the driver's side of the dash at a junction of six vacuum tubes.
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