A/C problem.

:(A/C in my 2002 Chevy Suburban works great, going down the road, even with temps going up to 117 degrees in the Pahrump desert of Nevada.
But when standing still or in park it seem's like the A/C just gives up and stops working.
Now as soon as you start moving again the air starts blowing so cold it will freeze you out.
Now this is a belt driven fan with a clutch and not electric.
I do want to put a pushing fan on the front of the radiator to help.
The car has has never got hot or even attempted to get hot, even climbing big mountains with the A/C on and towing. Any idea's???
And can anyone recommend a good pushing fan that will fit my suburbans radiator.
Thanks for any help with this problem.
Kurt

Sounds to me like your refrigerant pressure may be a little low. When you're at speed the compressor keeps the pressure up, but when you're idling the pressure goes low and the system pressure switch cuts off the compressor to prevent damage. Once you take off the pressure comes up, and it's cooling again. I'd have the refrigerant pressure checked.

If it's not refrigerant or receiver/dryer then the next thing will be to talk about your fan, clutch and shroud. I would not put a pusher fan on, as it will restrict air flow for your mechanical fan all the time, especially going down the highway. You may introduce a cooling problem with a pusher fan.

No the Freon is right where it's supposed to be Roger.
I do have about 150,000 miles on it now and have never replaced the compressor
do you think it might just be worn out??? I did hear that there was some kind of switch
that can get over heated under the hood, and shut off the compressor.
How do I check the fan clutch, to tell if it's bad???
Kurt

I think it's more likely the clutch on the fan is worn out @ 150K miles. There's a few switches under the hood on an a/c system. But if the system gets cold...??..??

Can you verify the compressor clutch "pulls in" at idle? If it doesn't, then it'll never get cold in the car.

IMHO, I think both Roger and 34-40 are on the right track,
ie., say the clutch fan is bad and not pulling enough air through the condenser at idle, this causes a high head pressure condition resulting in the HIGH pressure switch turning off the compressor, as the speed increases, air flow cools the condenser lowering the head pressure back into its normal operating perimeters and the switch turns the compressor back on.

I had not seen Mike's or 36Sedan's comments when I started this, and then was away for a bit....

When it's idling and not cooling, pop the hood and see if your compressor clutch is engaged, spinning the compressor. If not then you have a problem with the compressor controls. If it's engaged and spinning the compressor then increase your rpm to 2500 to 3000 and see what happens to your cooling. If your freon pressures are right where they are supposed to be (low pressure and high pressure) then your compressor is likely OK. The only switch I know of is the refrigerant pressure switch - gotta have a base system pressure to engage the compressor, but also trips out if the pressure gets too high. I didn't think that your fan clutch might be bad, thinking that you'd be hearing it, and your cooling wouldn't be working right but what Mike & 36 say sounds right to me, too. Here's a link to a very basic how-to on checking fans - How to Test My Thermal Fan Clutch | eHow Hayden makes good replacements, if you find it necessary, improving on the OEM fan.

I agree that a fan clutch check is important.....I was suprised what difference it made when I changed one on my Chevy truck. The fan was easy to spin by hand (with the engine off of course) but after the new clutch was installed, it was noticeable harder to turn. My fan was not moving enough air at idle and at speed, the fan was not needed. Fan clutches are cheap to buy and easy to change.

I have changed a few in the past but I never had this problem before with the A/C.
Thanks guys for the help.
Kurt

Sounds like it's freezing up to me. Try turning the temp up a bit when you stop so it's not trying so hard.

Well you guys called it!!! It was the fan clutch.
I turned it by hand and it seemed to be tight like the new one is.
But these have a little metal thermostat coil on the front of them.
So I guess it tell's them when to lock up when it's hot and when not to.
The tension seemed to be the same on both when they were cold though.
But I started it up and got inside and turned on the A/C and there it was, cold air.
Usually it does not get cold even when revving the engine to 2500 rpm's.
So thanks again for all of your help and input.
Kurt

That's good news Kurt!!! Glad to hear it's back on track.. Thanks for reporting back, it's nice to hear the resolution to a problem.

Well the one problems fixed, now I have to figure out why when I go thru a car wash the A/C goes out till it dry's out again.
I figure the water is grounding out something some where till the water dry's up, but where do I start looking???

Quote:

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Originally Posted by vara4

Well the one problems fixed, now I have to figure out why when I go thru a car wash the A/C goes out till it dry's out again.
I figure the water is grounding out something some where till the water dry's up, but where do I start looking???

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Pressure switch connections first (easiest), then maybe the clutch wires on the compressor? Not too many places to look out were it could be getting wet...

I got a feeling it will be the compressor because it's close to the front where the water can get to it from the car wash.
I think it's alot harder for the water to reach the pressure switch in the back of the engine compartment, but I'll try to seal them both.
I hate when the A/C does not work out here with this weather reaching 117 at times, The world record for heat was set about 50 miles to the southwest of me.
I heard it reached 134 degrees in the Mojave desert, That's just over the mountain as the crows fly. Bet those are some mighty thirsty crows too.
The bad thing is it does it in the rain as well, then you end up with foggy windows and if you try to vent it get's muggy in the car.
What's the best way to seal them??? Electric tape or what???

http://en.wikipedia.org/wiki/Death_Valley

Quote:

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Originally Posted by vara4

The bad thing is it does it in the rain as well, then you end up with foggy windows and if you try to vent it get's muggy in the car.

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Might be water is getting into the heater/evaporator box and is freeze up the coil, check the seals at the pipes going through the firewall.

I'll check that and make sure it's good and sealed too.
Thanks Kurt

If it's an electrical connection getting wet then you're shorting to ground through the water. How to fix it will depend on where you find the problem. Might be as simple as a glob of silicone allowed to cure. Tape is not going to block moisture.

Thanks Roger, I was thinking that too.
Had a problem years ago when I did that with a alt. wire.
It broke the connection and then I had to scrape it clean again to get the alt to charge.
Probably just one of those weird things that happen once in awhile.
Thanks Again. Kurt

IMHO, usually if water is causing a short it blows the fuse, water however that gets on the connection can cause corrosion to form which usually leads to an intermittent or complete connection failure.

Your description of high humidity in the rain from your heater leads me to believe that outside water is getting into your heater/evaporator box, causing the evaporator to freeze up, which in turn will cause the pressure switch to turn off the compressor. Locate your evaporator condensate drain hose (the one that drips water after running the A/C), gently pour some water over your A/C and heater hose connections where they enter the firewall, if water comes out the drain hose you have your culprit.

36 sedan we only get high humidity when it's hot out and it's raining and the A/C won't come on.
Now if we go thru the car wash it goes out, but after driving for about 15 minutes to a half hour in dry conditions in will come back on.
But I guess it takes that long for what ever got wet to dry back out again.
Kurt