Thanks guys.  Now this is beginning to make sense. It really helps to
understand to know when to quit.

John

On Sep 29, 2016 19:58, "Dennis Haynes" <d23haynes57@hotmail.com> wrote:

> That trinary switch does a number of functions. It is both a safety limit
> and it operates the radiator fan intermediate speed based on pressure on
> the high (condenser) side of the system.
>
> The first function is to ensure there is some pressure in the system to
> allow the compressor to turn on. Since it is on the high side once the
> compressor turns on this switch will continue to be satisfied even if only
> air is in there. At around 275 PSI it should put the radiator fan into that
> intermediate speed. This is done operating the relay (I think space 5) in
> the fuse box to apply power through the other side of the fan resistor to
> bring up the speed. At some higher pressure it should turn the compressor
> off.
>
> The fact that you blew the back off the switch indicates that you have a
> blockage in the system and that the safety circuit didn't do its job. You
> probably also compromised other parts of the system. My bet if the system
> was just cleaned and flushed and whatever is that there was too much oil
> that couldn’t pass through the port in the Receiver dryer and the system
> went into hydraulic lock up. The compressor is probably toasted also. Look
> for bubbles in the hoses, cracks in the condenser and distortion or the
> blow port on the dryer failing.
>
> Summer is over so you some time to recuperate. It is time you get a pro to
> do this complete and pay your dues. Someone can get hurt here.
>
> Dennis
>
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf
> Of John Rodgers
> Sent: Thursday, September 29, 2016 3:36 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: '91 Carat AC - again!
>
> I sure have struggled with this system.
>
> Just above the high pressure service port there is a port for a shraeder
> valve. Scriwed onto that port is an electrical deviced called a "trinary
> switch". I have no I dea what it does or how it works. Seen from the
> shrader valve end there is a pin that obviously works asinst the stem in
> the shraeder valve. It is electric -4 wires - but what does it do? How does
> it work? What does it regulate?
>
> Driving down thevroad I heard a loud pop, then a whistling like air from a
> tire. I stopped to investigate and foundcthe bach of the trinary  switch
> blown off, suggesting that the shraeder valve underneath had failed. I
> removed the switch, replace the shraeder valve, and reinstalled it,
> thinking I MIGHT just put the rubber seal back in place, and all would be
> fine. NOT!!! The minute I added a can of refrigerant and presurerized the
> system, the seal popped and I was back to square 1, suggesting the shraeder
> valve failed again.
>
> Not knowing the relationship of that trinary switch to the shraeder vslve,
> I'm reluctandcto trymit again until I learn more about it.
>
> Can anyone enlighten me?
>
> Thanks.
>
> John
>