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pressure switch removal

nextlevel on Tue August 28, 2007 6:22 AM User is offlineView users profile

Year: 1990
Make: chevy
Model: suburban
Engine Size: 350
Refrigerant Type: 134a

I think the pressure switch that mounts on the accumulator has gone bad and will not let the compressor cycle. The air works very well but the compressor never cycles off. Is this a problem and can the switch be removed and replaced without discharging the system?
I have a 1990 chevy suburban with a 350 engine and retrofitted for 134a.

James

Chick on Tue August 28, 2007 6:31 AM User is offlineView users profile

The cycling switch on the accumulator will only cycle the compressor off when it drops in pressure to the set low side pressure of the switch. Usually between 19 and 25psi.. What are your pressures, both high and low? That switch works on the "low' side.. If it's hot out, and humid, it may never cycle, as the pressure may not drop since the evaporator is removing heat and water from the air passing over it..To see if it's working properly, get the car out of the sun, run the ac until it's cool inside, then lower the fan setting and watch the low side guage.
Another eeason it may not cycle is if the retrofit wasn't done correctly, (Air in the system), bad compressor reed valves (not allowing low enough pressures) bad fan clutch (poor airflow over condenser keeping pressures up)
On cooler days, or when driving on the highway it may cycle more. We would need both high and low pressures to see if it's operating properly, or if there is a problem with the system and/or switch..Hope this helps..

But you can unscrew the switch without loss of refrigerant. There is a shrader valve below it. Be sure to change the O ring before replacing the switch..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

nextlevel on Wed August 29, 2007 7:40 AM User is offlineView users profile

When we replaced the compressor and the accumulator and the orifice tube I pulled a vacuum and then began charging the system. The compressor cycled fine up until a certain pressure and then it did not cycle anymore. Of course it was hot outside and the humidity was high. The low and high pressures were good but as of right now I do not remember the actual numbers. They were somewhere around 40 and 200.

The air works very well. My son is using the car right now but when he comes over I will run the check you mentioned. Thanks for the advice.

James Hart

Chick on Wed August 29, 2007 7:44 AM User is offlineView users profile

It sounds like it is working properly then. Feel the inlet and outlet of the evap, if both the same temp, leave it alone... If it ain't broke, don't fix it...Hope this helps..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

mk378 on Wed August 29, 2007 8:50 AM User is offline

It probably will not cycle at idle on a hot day with a R134a conversion. Cycling is necessary only to keep the evaporator from overcooling and freezing up. Until that is about to happen, you want the compressor on constantly.

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