Automotive Air Conditioning Information Forum (Archives)

smokey0810 on Tue July 27, 2010 11:41 AM

Year: 1995
Make: Chevy
Model: Caprice
Engine Size: 5.7L
Refrigerant Type: 134a
Country of Origin: United States

'95 Chevy Caprice police pkg. Just replaced the hoses on the back of the compressor and the receiver/dryer and orafice tube.
Threw some freon in, blew cold.
Drained the system via 1 can of freon on low pressure side, and pressing the high-pressure side with a screw driver (system off)
Didn't blow cold, and not accepting any more freon.
Vacuumed out the system, held at 40PSI on the low side.
Added freon, still blowing hot.

High pressure line is SCOLDING hot. Other line is ice cold.
Lines going to the car, one is ice cold, other is barely warm to the touch.

All vacuum controls and wires inside the cabin seem to be up to snuff.

As of this morning, compressor cycles on & off, like it's low on freon....Yet the system won't take any more.

153K Miles on what I suspect is the original compressor. Clutch assembly has some play in it.
Any thoughts?

mk378 on Tue July 27, 2010 12:01 PM

You need to start over and do it right. You can't just replace parts and "throw some freon in": that makes a mixture of refrigerant and air which will not cool properly.

Open the system and check the orifice tube (again, to see if any debris moved into it). Use proper tools get a full vacuum on both sides. Charge to the specified weight and measure both pressures.

GM Tech on Tue July 27, 2010 12:16 PM

need high side pressure- how do you know the cycling is not high pressure cut-offs otherwise?

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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......

iceman2555 on Tue July 27, 2010 7:05 PM

ANY THOUGHTS???? When I first read this post.....ohhhh well......lets address some of the 'installation' procedures.
First...installed some parts...threw in some refrigerant....and it blew cold.....that boggles my mind !!! It boggles my mind that it blew at all...much less cold.
Then the system was 'drained', it is assumed that this was a procedure to remove air and moisture.....by adding refrigerant into the low side......WHILE depressing the high side schrader to allow the refrigerant to purge the system !!! However, can not say that this is the first time have heard this procedure being utilized. Never seen it work...but have heard of it before.
Now it does not blow cold....and will not accept any more refrigerant.....will wonders never cease......First...it is not the job of the compressor to 'pull' refrigerant into the system. That is an entirely different procedure.
Then...let's see....."Vacuumed out the system, held at 40PSI on the low side".....how was the system evacuated.....and 40psi is not a vacuum...this is a positive pressure within the system.
High pressure line is hot....think the term was 'scolding'.... and the 'other' line is 'ice cold'....not exactly sure which line is which....but from this description...sounds like a serious restriction....or could be air in the system.....could be moisture freeze at the orifice tube.....
There is only one way to arrive at a possible system performance diagnosis. Start over and square one.
Insure that the orifice tube is clean....replace the darn thing...they are not expensive. If contaminated....let us know....may need to replace other parts.
Insure that all connections are correct, o rings are in place and fittings are tightened.
Rent or otherwise obtain a vacuum pump. If a set of gauges is handy...use them....if currently using a single gauge....possibly the one that came on one of the refrigerant cans...get rid of it and obtain a set of gauges.
Correctly attach the hoses.....connect to the vacuum pump and evac the system. Operate the pump for 5-10 minutes.....close your gauges....observe gauges for loss of vacuum...should not loose more than 2 in/hg in 5 minutes. If leaking...locate and repair leak. Re energize pump...operate for a min of 30 minutes...45 is good.
Close gauges...remove pump from center/charging hose. Obtain necessary refrigerant...requires 28 oz....need three cans. The vehicle takes 28...your hose/manifold will require app 4 oz to precharge....that is 32....some refrigerant will be left in each can....so it will require 3 cans...
Recharge the vehicle...MAX AIR...HIGH BLOWER....IDLE SPEED...DOORS OPEN. Charge until the evap inlet and outlet are the same temp. Use your fingers to determine this. The evaporator outlet (line going to the accumulator) should be the same temp as the inlet line....or even a bit cooler. This is the correct charge for the vehicle.
Retest and post pressures....after all kidding aside....we are here to assist in any way......Good luck!!!

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Thomas Jefferson