Trinary switch ls3 Fan on with a/c

[redzo6]

Hello, I have a crate ls3 engine. I am hooking up a trinary switch and want the fan to come on when the A/C turns on. My relay is from VA and it has 5 wires. 1 full time power, 1 ignition power, 1 fan wire and 2 white wires. My question is do I hook up all the wires as in the diagram and ground both white wires and leave the blue wire on the trinary switch unhooked?

Also my rpm is dropping and sometimes shutting engine off when the a/c is turned on. Do I need to get the engine tuned?

[DT69Cam]

I'm almost at this same stage. Would love to know what steps are needed.

[dhutton]

I think this diagram is pretty clear. You want the second drawing with the trinary switch. If you ground the white wires the fan will always be on.

http://www.vintageair.com/Instructions2013/900471.pdf

You are going to need to use the second white wire to allow your ECM to turn on the fan.

You only have one fan? Most setups I have seen have two fans.

Don

[randy]

what harness are you using?

[dhutton]

Originally Posted by randy

what harness are you using?

I was wondering same thing. Doesn't your LS harness already have a fan relay? If it does I am not sure that the VA relay is needed. Just use the trinary switch to activate the LS harness relay, assuming the ECM pulls the fan relay coil to ground.

Or if you are stuck on using the VA relay just use the ECM and VA relays to power the fan in parallel.

Don

[redzo6]

The LS fan relay will not turn on the fan when the a/c commands it too. It only commands it to turn on when the engine temperature reaches its limit.