Trinary Switch Selection

Friendly format provided to inquire about automotive a/c systems.
Archived Forum

Moderators: bohica2xo, Tim, JohnHere, Dougflas, HECAT

Posts: 14
Joined: Sun Jul 10, 2016 11:40 am

Trinary Switch Selection

Postby 69-er » Fri Aug 03, 2018 6:16 pm

I am installing an electric fan in my 92 Chevy truck to replace the mechanical fan. It is currently running 134A with a rebuilt system consisting of new o-rings, new compressor, accumulator, orifice tube, parallel flow condenser and a flushed system. I'm looking for a recommendation for a trinary switch to control the fan.

Instead of using a typical universal switch with wires or spade terminals I would like to find one that has the connector directly attached to the switch and which also includes the matching connector. I've been able to find a few universal ones and some for specific applications but I'm not sure what the correct pressures should be for this setup. I'm more worried about the fan switch closing pressure. It seems like there is a fine line when it should turn on. I don't want the pressure so high that it waits too long to turn on the fan like when at a standstill.

Any ideas what a good pressure spec would be? Actual part numbers would be a plus! I guess I could base it off the high side pressures while at a standstill and going down the road as a last resort.


Posts: 42
Joined: Fri May 27, 2016 12:46 pm

Re: Trinary Switch Selection

Postby 71403 » Sat Aug 04, 2018 6:42 am

Fan should come on with the a/c request not pressure alone. If using two speed fan(s) can use high pressure switch to activate the high speed.

Ideally the fans should disable over ~30mph. The stock ECM doesn't control fans but if you're into tuning there are code patches and upgrades to allow for it.

Return to “Automotive Air Conditioning Forum”