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AC accumulator frosting over when AC is not on?

fedupey1 on Tue June 29, 2010 7:33 PM User is offline

Year: 1994
Make: Chevrolet
Model: Suburban
Engine Size: 6.5 TD
Refrigerant Type: 134
Ambient Temp: 70s
Country of Origin: United States

For a while I noticed a small drip in the passenger footwell, and a larger drip off the frame rail approx. behind the front passenger wheel. In both cases the drip stops shortly after the engine is off, and the dripping fluid is clean water, not engine coolant.

After a 50-mile run at 80 mph without turning on the AC, I took a look under the hood and noticed the accumulator was completely frozen over from top to bottom. Within a minute or so after the engine was off, the ice had melted and it seemed like the source of the drip. My questions are: 1. is it normal for the accumulator to freeze over when the AC is not on, and 2. is it normal for it to freeze over at all during normal operation?

Thank you for your advice.

TRB on Tue June 29, 2010 8:13 PM User is offlineView users profile

Sounds like the compressor is turned on even though you think it is not. No way for the accumulator to frost over if the system is equalized. That's why you see it melt back down when you know the vehicle is turned off. Probably a control head issue or bad signal from the computer.

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mk378 on Tue June 29, 2010 11:18 PM User is offline

Could also be a stuck compressor relay though I think that would run down the battery if you parked the truck for more than a day or so.

bohica2xo on Wed June 30, 2010 1:56 AM User is offline

Yes, it is normal to frost an accumulator during operation - especially with ambient temps in the 70's.

No, it is not normal to see this with the system "off".

Before you put the key in the ignition, make sure the A/C is off. Start the engine, and look at the compressor. The face of the compressor pulley is the clutch. It should be stopped.
If it is turning, shut the truck off & pull the connector for the clutch coil. Start the engine again, and check the clutch. If it is still turning, then the clutch assembly is frozen or has no gap. If it is not turning the issue is electrical.

If the compressor was NOT turning when you first started the engine, turn the A/C on. Once you feel cold air & know the compressor is running, turn the A/C off but leave the engine running. Check the compressor. If the compressor is still turning, shut the engine off, wait a minute or two & re-start with the A/C still switched off. Is the compressor stopped?

B.

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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

GM Tech on Wed June 30, 2010 7:39 AM User is offline

Sounds like someone hot-wired your compressor-- have you had a/c help recently?

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

fedupey1 on Wed June 30, 2010 1:35 PM User is offline

I started the engine with the AC button off. The compressor clutch was stationary (not turning).
I pushed the AC button. The clutch started turning, and the AC indicator lit up on the climate control display. Soon the air was blowing cold inside the truck.
I drove a couple of miles and checked again. The compressor clutch was still turning. I pushed the AC button off, the clutch stopped turning.

So - during this test at least - it looks like everything worked as it should, is that correct?

The other day the accumulator was frosted over even though the AC was off. Is it possible for the compressor to be on, yet no cold air blowing inside the truck?

Thank you all for your responses.

GM Tech on Wed June 30, 2010 1:43 PM User is offline

Do not forget, that the a/c is "on" when in defrost or blend mode---even though the a/c lite does not lite in these modes.....it is a funny way the truck designers have of not letting you worry about the a/c being on when you did not select it- they choose when you shall see the light on.

Other than that- put the blower on low speed and recirc mode and see if the compressor will cycle on and off--in low ambient (nightime is best) conditions.....if not, you may have a stuck shut cycling switch (on accumulator)

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

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