Clutch cycling too much

QA2 on Tue March 13, 2012 8:32 PM

Year: 1984
Make: Volkswagon
Model: Cabriolet
Engine Size: 1.8
Refrigerant Type: R-134
Ambient Temp: 75
Pressure Low: 30
Pressure High: 150
Country of Origin: United States

I pulled the vacuum and charge the system after installing a used compressor. The low side would hang around 20 move up to 30 and the clutch would kick off until the pressure reached 50. Once it reached 50 the compressor would kick on and the pressure would drop to 20 and the same process would start over again. The compressor cycles like this every 30 to 40 seconds. The high side would hang around the 125 mark and spike to 150 when the compress would kick off.

I have been searching the VW boards and this board for similar problems but I did not find any so can anyone give me some advise on what direction I should go. THanks in advance.

QA2

JACK ADAMS on Wed March 14, 2012 11:16 AM

Looks to be low on refrigerant, not sure. what compressor do you have in this application? How much refrigerant was added?

mk378 on Wed March 14, 2012 6:49 PM

The #1 question is is the vent air getting cold? It sounds like normal operation in cool weather.

QA2 on Wed March 14, 2012 7:08 PM

THe compressor is a sanden. Added around 40 OZ of R-134 and vent air will go down between 60 and 55 degrees.

TRB on Thu March 15, 2012 12:16 AM

An 84 had an R12 capacity of around 30 ounces. Having those pressures with that much R134a in a R12 system. Leads me to think we got more going on here besides why is my system not cooling.

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QA2 on Thu March 15, 2012 7:05 AM

According to the factory manual the system holds 40 oz, plus or minus 2 oz. of R12.

bohica2xo on Thu March 15, 2012 11:54 PM

75 ambient can make testing harder. Do a full load test & collect some pressure data:

Both doors open, cabin fan on highest speed.

Raise engine rpm to 2,000 Hold at that speed for 5 minutes to stabilize.

Record high & low side pressures while the engine speed is still @ 2000 rpm.

B.

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