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I have a 1988 with what appears to be factory air conditioning. It works, blows, cold and does a good job. However, it seems that the engine runs a bit rough when the compressor is engaged. The idle speed seems OK, although I don't have a tack.

Any ideas on what causes this or how I could make it better? I'm trying to get all her rough edges addressed and this is one of them.

There is an A/C solenoid that bumps up the idle speed when the AC is engaged to counteract the drag on the system.

This is either not working, or it is not adjusted properly.

if the idle RPM is too low with AC/trans engaged could bump the idle up 600-800 rpm , if the engine doesn't diesel when shut down your good, let everyone know what you find

Stuka wrote: ↑Sun Jul 17, 2022 4:05 pm There is an A/C solenoid that bumps up the idle speed when the AC is engaged to counteract the drag on the system.

This is either not working, or it is not adjusted properly.

The anti-diesel solenoid (carb solenoid in the picture taken from the 1988 wiring diagram) is energized whenever the ignition is in the ON position, it is not controlled by the AC circuit. If you are running the original YORK compressor, they do tend to be a bit rough. You can increase the idle speed a little to help. A swap to a Sandeen compressor will help some but is expensive.

will e wrote: ↑Sun Jul 24, 2022 7:16 am

Stuka wrote: ↑Sun Jul 17, 2022 4:05 pm There is an A/C solenoid that bumps up the idle speed when the AC is engaged to counteract the drag on the system.

This is either not working, or it is not adjusted properly.

The anti-diesel solenoid (carb solenoid in the picture taken from the 1988 wiring diagram) is energized whenever the ignition is in the ON position, it is not controlled by the AC circuit.
anit diesel solinoid.jpg

If you are running the original YORK compressor, they do tend to be a bit rough. You can increase the idle speed a little to help. A swap to a Sandeen compressor will help some but is expensive.

When I was reading through the TSM for his year, it has a solenoid listed as being associated with the A/C. But that was like a week ago, so I don't have that tab open anymore.

You sure it has a solenoid for the a.c ? Either mine isnt working or ? Because i do have that pin solenoid thing by the throttle.. and that thing always is negaged to keep the idle higher than 600. Even if you want the idle lower it keeps the throttle at 600. Im not sure what controls it or turns it on though. But its always on.

It sure as hell doesnt come on when the a.c is on.. and even if it did it wouldnt bump the idle higher than 600anyway

I know my truck is noisier when the AC is on. Its not a failing compressor because its been doing it from Day One and is 4 years old. Im thinking maybe bad motor mounts--just too lazy to check. Maybe you can check yours and let me know-LOL