The high side pressure switch in my '87 Camper closes the 2nd stage relay that puts the radiator fan on its 2nd speed; it doesn't shut off the compressor. It operates when high side pressure goes above 220 psi. Mine comes on regularly in stop and go traffic in the afternoon, but the A/C still keeps working. As soon as I can get moving again, the 2nd stage relay opens and the fan goes back to the slowest speed.

My radiator fan goes on high speed only when coolant temperature gets to a certain point, but even then the A/C compressor still functions. I have found no mechanism in the high side of the A/C system that will turn the radiator fan on high or shut off the compressor.

Thanks,

Tim

Kim Brennan <kimbrennan@MAC.COM> wrote:
In your AC system you have a relay behind the rear most drivers side
pillar. This relay checks the pressure of the refrigerant line on the
high side. If it is too high, then the AC system is either overcharged,
or you aren't getting enough cooling up front. No matter what the cause
the relay will turn off the compressor and turn on the radiator fan to
high speed until the pressure in the high side comes down to acceptable
limits.

At highway speeds you might not even realize this is happening until
you suddenly realize your AC system isn't giving you cooled air
anymore.

Note there is a low side AC relay too. This makes sure that there is a
minimum charge of refrigerant in the AC system before it will allow the
compressor to kick in.

TJ Hannink
Goldibox - 1987 Vanagon Camper, Wolfsburg Edition
1981 Bluebird Wanderlodge, FC-33
Winter Park, Florida
http://home.earthlink.net/~tjhannink/
http://groups.yahoo.com/group/wolfsburg_campers
http://groups.yahoo.com/group/FC_wanderlodge
FAVOR website:  http://home.earthlink.net/~clubvanagon

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