Date:         Thu, 17 Jul 2003 00:59:11 -0400
Reply-To:     Kim Brennan <kimbrennan@MAC.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Kim Brennan <kimbrennan@MAC.COM>
Subject:      Re: Help with A/C High/Low pressure sensor requested
In-Reply-To:  <20030716201130.87646.qmail@web41008.mail.yahoo.com>
Content-Type: text/plain; charset=US-ASCII; format=flowed

I'm not saying your diagnosis is wrong, but have you checked the
thermostat switch (that which controls the temperature)? This is simply
a rheostat (variable ohm resistor), but if it has failed, it will
prevent the compressor from kicking in. Mine failed on my 86, which
meant my AC wasn't cooling.

It's relatively simple to check, with just a regular ohm meter.

FWIW, the compressor doesn't cool the freon. Rather it heats it
up...the heat exchanger (i.e. condensor) in the front of your Vanagon
dissipates the heat and then the cooled liquid evaporates in
the...evaporator (which is what is up in the rear of your Westy.) The
process of evaporation sucks in the heat locally (which you feel as
cooled air.) Then the freon (now essentially in a vaporous state) is
compressed (and heated) again to a liquid state.

On Wednesday, July 16, 2003, at 04:11 PM, Joel Cort wrote:

> I have not been able to get the compressor to kick in and the R134
> pressure is correct in the system. I believe that the problem is with
> the High/Low Pressure sensor. If I unplug the 4-wire connection to
> this sensor, and I jump two of the terminal I can get the compressor
> to kick-in and start cooling the Freon. This would mimic the
> low-pressure sensor switch. When the pressure is too low, it starts
> the pump up with the correct ambient temperature. If I jump the other
> two wires I will get the 3rd stage radiator fan to kick-in. This is
> what the high-pressure sensor should trigger when there is too much
> pressure in the circuit.