Automotive Air Conditioning Information Forum

Where can a trinary switch be placed in a TXV AC circuit?

(This application is a 80-91 VW Vanagon and my question is general?

I'm wondering if it can be on the high side vapor line right at the compressor since pressure should be the same for liquid or vapor between the compressor and TXV, but maybe the switch needs to sense liquid?

Often it is on the receiver/ dryer RD which is the liquid line.

Google search was not clear, one source said downstream of condenser which would indicate liquid. Searching on here for "switch" wouldn't give results citing the term is too common.

I already have a switch at the front on the RD which is right after the condenser. I'm looking to place a second switch at the rear of the vehicle where the compressor and evaporator are to take out 40ft of 14g (20ft out and back) running from the compressor to the switch at the RD. I'd use the pressure cut out feature of the switch at the compressor location and leave the RD location to serve the fan activation feature. Alternately there appears to be a combination of fittings that I could put one right in front of the TXV which would put me in the liquid line but a switch right at the compressor would be more convenient for several reasons.

Thanks

As you stated usually at the r/d.
It is not clear why you need a second switch.
Any pressure change at one certain point in the system will be felt almost immediately by the entire system. IMO the one sw is sufficient

tbirdtbird wrote: ↑Fri May 24, 2024 2:11 pm.
It is not clear why you need a second switch.
Any pressure change at one certain point in the system will be felt almost immediately by the entire system.

Thanks for the reply.

I'll conclude that on the high side it doesn't matter if it is in the vapor or liquid section. If that is not correct please let me know.

Re why second switch

andrew vanis wrote: ↑Thu May 23, 2024 7:26 am to take out 40ft of 14g (20ft out and back) running from the compressor to the switch at the RD.

All that matters to a pressure switch is pressure, whether vapor or liquid

Thx for the confirmation.