The A/C on my truck works perfect as long as you are above 1k rpms. As soon as you go to idle it cuts out and quickly begins blowing warm air. Rev it a bit and it blows nice and cold. Any idea what the problem could be?
thanks -jon

 

Did it just start doing that or has it always done it? Is the clutch itself on the compressor disengaging? On my 91 PU there's an adjustment dial behind the glove-box that lets you change at what RPM the clutch disengages.

 

low charge maybe? have you noticed if the compressor is turning when at idle?
when the charge is just a bit too low, at idle the compressor may not be spinning or spinning fast enough to maintain sufficient pressure in the system to keep cold.

 

X's 2 on the pressure; I would check that first...

 

Yeah, Mine did the same thing after the switch to r134a, took a while to realize that if u have too much or too little the clutch will kick out at weird times, you kinda have to find the sweet spot as far as pressure goes...at least thats how mine was

 

Even my '97 didn't cool very well at idle, and I'm a licensed A/C tech. There's just not enough volume being pushed at 6-700rpm on that compressor. I thought about it then and came up with a few ideas;

► Smaller AC clutch & pulley, modded to fit the stock compressor.
Problems here are obvious: Sourcing one and making it work.
► Use a VSV to induce a metered route for air to flow around the IAC.
My only question there is would the PCM throttle back the IAC to try and set the idle at it's prefered 700RPM, or would it stay put and let the idle come up.
► Larger refrigerant compressor.
Same obvious problems; sourcing a larger compressor that will fit with reasonable modifications, and can run a V-belt.

 

on the 22re, there should be an AC idle up valve that raises the idle speed to compensate for the compressor drag on the engine it is also adjustable. I have mine set to run the engine up to about 900 when the AC is on.

 

yeah, same here with the idle up valve; I just adjusted mine so it brings the idle up about 200 rpms more with the ac on than off.

 

The problem is airflow. While you may have a fan clutch problem, the biggest problem is that at 1K rpm you really aren't moving forward and the fan isn't turning very fast. This equals no flow over the a/c coils and no cooling.

 

Besides the A/C idle up valve, there is also the A/C Amplifier (behind the glove box) that has an adjustment knob to set the low idle RPM cutoff point. So if either of those are out of adjustment or not working right, the A/C will cut out at idle. So make sure the idle up valve is working and does bump the idle speed up 100 RPM or so with the A/C on (white knob adjusts the idle speed). And make sure the low RPM cutout is a little below the normal idle speed.

 

How do you adjust the idle up valve and where is it located?

 

It sits atop the intake:


Turn knob one way to speed up the idle, the other way to slow it down.

 

Awsome, thanks!

 

Thanks for all the replys! Its pretty much done this since I have had the truck. Im going to check the freon pressure and make sure the compressor clutch is staying engaged at idle. Also going to turn up the idle screw abit. Does the Idle screw that is pictured only adjust the idle in regards to when the compressor is running?

 

Yes, only adjusts idle speed when the A/C is running or when power steering (if installed) is used at idle. Check for clogged vacuum lines, that is very common.

 

Not intentionally trying to contradict you here, but my 88 runner has AC and turning it on results in about 100-150 rpm rise in the idle speed. Turning my steering wheel at idle does not increase my idle speed....

 

It should, assuming the p/s pressure gets up high enough to open the VSV atop the p/s pump. And are those vacuum lines clear? On my '85, the inlet port from the intake was packed solid with carbon. Needed to use a drill bit to auger it out.

 

I get what you are alluding to. However, I can step full hard on the brake pedal and quickly turn my steering wheel from lock to lock and the engine speed does not raise nor drop appreciably from 750, but turning the AC on causes the idle to raise to approximately 900. Turning the steering wheel with the AC on doesn't affect the engine speed either.

 

Sounds like you have a plugged cacuum line.

 

Checked it out today, at idle speeds the compressor clutch is cutting out. If you rev it up just a bit and it kicks on. I tried adjusting the vacuum screw in the above photo but it made no difference, no mater which way I turned the screw. So, I just turned up the idle speed at the throttle body to keep the a/c on. Any reason why adjusting the vacuum screw would not work?