Hi all,

Great forum.

This question regards a 1988 pickup, auto, fuel injected, 2wd, 22REC..

When I got it the AC worked very weakly and only when the truck was running on the highway. At slow speeds and idle it didn't work.

I took it in and the freon (it's an R134A conversion) was low and a connector was leaking. The freon was charged and the connector replaced.

The AC would still only run when the RPMs were up over 1000...probably closer to 1,500. At least it was blowing cold though when driving.

So, next up was an adjustment of the AC amplifier (might have a different name...it's a little black unit that is behind the glove box). It has a nob which allows you to adjust the RPMs below which the AC shuts off. We adjusted it so the AC would run at idle. However, with it like this once the truck is put in gear the RPMs drop and the engine dies.

So, I am unsure of what to do next. In a newer car it seems when the AC is applies RPMs compensate and bump up a bit? This doesn't do that...applying to AC drops the RPMs. In order to get the AC to run at idle it is causing the engine to die once shifted into gear.

The truck is idling without AC 900 or so (goes down a bit after I've been driving).

I recently cleaned the intake on the throttle body.

Any ideas of what to try next?

Thanks

 

This thing here:
http://www.4crawler.com/4x4/CheapTri...ine_Pix/7.html
Is how you adjust how much the RPM's go up when the AC is on.

At least, I am pretty sure that is what you need.

B

 

Thanks for the link. Great photos.

I tried that adjustment screw and no luck.

Is there a valve that could be bad? Some sort of feedback to the high idle?

 

when you say it only runs when going down the hwy does the compressor shut off at idle or does it just not cool?how is the engine temp?if not cooling at idle & compressor runs shut off engine & use a garden hose to clean out the fins on the radiator spraying wat into them from the engine side.also make sure there is not a bunch of crud between the condensor & radiator.also make sure the fan clutch is wrking properly.it may not be drawing enough air thru the condensor to cool it off

 

The compressor runs and cools when the RPMs are up...so going down the highway or if I sit and rev the gas. The compressor doesn't run (doesn't spin) when the vehicle is at idle.

Engine Temp seems to be fine. It hovers a little below half way on the gauge on a warm day after an hour of driving.

Radiator isn't dirty...it's a farily new one. Fan appears to be working well.

It seems to me that somehow the AC is failing to kick the RPMs up when it comes on. I can adjust the AC on the amplifier control box to run when the car idles. However, when I do that the RPMs go down. And then get low enough in gear that it dies.

Shouldn't the AC kick the RPMs up to compensate? I did adjust that high idle screw in the photos above and no luck.

 

the clutch on the compressor will only kick in at a certain rpm. mine does the same thing. check your chilton manual, im fairly certain there should be a way to adjust the compressor clutch to kick in at a lower rpm.

as for me, i like rollin with the windows down instead of the ac.

 

Barnstormer is right that is the a/c idle-up valve and you can adjust it but there is a VSV that actvates the idle-up valve and if it doesnt work then it wont idle up , thats the small vac. hoses follow them to the VSV.