88F150 300 6

When I turn the ac on the air blows cold but the motor cant idel without giving it gas. when I turn the ac off the motor has no problems. heat works fine on floor and vent but in defrost or floor/defrost it does the same thing as ac. so does the compressor run in defrost? I have some vacume problems in ac but in heat there seems to be no problem. I think that the compressor is a seperat problem. it still pumps but is realy hard on the engine.

And do i have to replace the compressor in order to have defrost?

 

Yes, defrost runs the compressor.

 

I was afraid of that. is there a bering or somthing that i can change on the compressor? and if there is, is it better to replace the compressor or to rebuild it?

 

Is the compressor clutch making any noises. If your engine is equiped with an IAC it may be bad. The IAC controls the idle. I guess I should have asked if your truck has fuel injection.

 

truck is fuel injected but it idles fine unless i turn on the compressor. and no the compressor clutch doesn't seem to make any noise other than kicking in. If the IAC (which i do not know what it is) is bad would it mess up the idle all the time or just when the compressor is running? one more thing my alt. meter drops in the red when I kick the compressor on.

 

Radial I don't think this is going to be his IAC since the a/c compressor isn't going to affect the IAC.

 

I think that's the answer to the problem right there. A seized electrical motor is going to cause a large amperage draw like your a/c compressor is doing. It sounds like the a/c compressor is seizing up. I'm not sure if/how it can be dissembled and repaired... Maybe someone else can chime in here.

 

On the throttle body there is a screw that looks like an old type idle screw, it is on the side and there should be a lever underneath it. Is that screw touching the lever? It should not be touching the lever. If you move the screw off the lever and the engine dies it is a good sign the IAC is not working. The IAC is on top of your throttle body and has two wires(I think 2or3) to it As far as the volt meter going into the red it could be a weak battery or alternator, or a short in the compressor clutch curcuit.

 

in a normal situation where should the needle for the alt. output be. in the middle or closer to the high side. mine runs somwhere around the low side of middle of the guage. also it pulsates with the blinker. is that normal.

 

for a temp fix that i did for a little while ws unplug the harness on the compressor then it wont engage did that all winter then forgot that i did that and plugged it back in the summer and it worked fine. Mine would try and kill the engine and the clutch started smoking so that is why i unplugged it for the winter

 

I haven't noticed the clutch smoking but it defenitly kills the engine. good idea for now on unpluging the wire harness. that way I can run my defrost this fall. I have all fall and all winter to pick up a compressor. this will allow me to get by. Thanks.
Any other suggestions are welcome..

 

Unplugging the harness on the compressor would be about the equivalent of just NOT turning on your a/c or defrost. That just means that when you turn the a/c or defrost on the compressor is not going to turn on. Although I think it will still turn on your condenser, but that is useless if the compressor doesn't work. Pastor, I'm pretty sure that your defrost is not going to work without the use of the a/c compressor, I could be wrong...

 

You need to fix one thing at a time. You have already determined you have one or more vacumn leaks. That will cause the engine to not idle properly. When the compressor kicks on, it loads the engine more, slows the idle, makes the vacumn leak even more evident, and slows the alternator output at the same time the electrical demand goes up. I don't think the dash volt meter is particularly accurate. Mine shows about 10-11 volts when the fan is on high, but a mulitester shows 13.5 volts at the battery.
If the a/c is cooling well, don't worry about it until you fix the other problem, or problems. When was the truck last tuned up? Have you pulled the codes from the computer? Need to be systematic in trouble shooting problems, or you end up working on symptoms instead of causes. Waste a lot of time and money doing it piecemeal.
The best way to test the Idle Air Control, IAC, is to unplug it while idleing. The truck should die. UNLESS you have a large enough vacumn leak to let it keep sucking air and running. DO not adjust the throttle body screw that looks like an idle stop. If you adjust it, eventually you will wish you had not.
Good luck Frank

 

It should be near the center and ther should be no fluctuation. It still indicates a weak battery or, alt. If your compressor works and only stalls the engine then it's OK. What I am trying to tell you is the compressor puts extra load on the engine and that the computer uses the IAC to step up the idle to compensate for the extra load if the IAC is not working the engine could stall. Also a weak battery, or alternator could cause several other performance problems IE voltage drops to ignition, computer, etc...

 

"Your right" It would make more since to replace the cheaper stuff first like the vacume line that i think is leaking. that has to be easier and cheaper than working on the compressor. Also I know that it needs done. I dont know anything about codes and I dont plan on adjusting anything with the idle because i would mess it up. I can turn a wrench pretty good but that fine tune stuff i need help with. Seems as though both my threads might turn out to be all symptoms pointing to the same problem and could have been discused in the same thread. Thanks for all the help I will post what happens after I replace the vacume line.