How are you putting fans on when running VA AC

[1970 CST Short Wide]

I understand that the fans (electric) need to be on when your AC is on. I have vintage air. How are you guys running your fans when the AC is on??

Thanks
Steve

[dec010974]

Good morning 1970 custom. I'm gonna assume that you are referring to the electrical part right? In most cases the LSx pcm commands the fans to run when the engine reaches a certain temperature. If you want your E fans to turn on when the A/C is turned on just set up the fan relay trigger off of the A/C on switch. This means that when you turn on your A/C, it will trigger your fan relay to turn on your fans. I hope this helps you out. This is my answer. There may be others.

#30-Fused Battery power
#87-Power to E. Fan
#86-Ground
#85-Power side of A/C on switch.
Note:#85 is not the power for the A/C. #85 will be the power/trigger once the A/C is turned on or maybe even the A/C clutch switch. Good luck.

[ls1nova71]

Easiest way is to use a trinary switch.

[dec010974]

ls1nova71, I gotta read up on this thing called a trinary switch. most of my hot rods don't have A/C.

[my56chevytruck]

use a trinary switch and or a wired switch in the cab to activate your fans.

[homemade87]

I agree with the trinary switch . Lots of advantages going thru the pcm . Best to have a dual fan set up with the three relay system but can be used for a single fan . The trinary uses the high pressure side to control the fans .

Here's where I did mine and it works perfect . http://67-72chevytrucks.com/vboard/s...hlight=trinary . Also just type in trinary and you will see a lot of info . In my opinion this is to only way to go .

[Hart_Rod]

Trinary wiring diagram

[68c10airstream]

If you can get the pcm involved in the on/off command of the compressor the pcm will automatically adjust the idle rpm for the incoming load and unloading. Without the pcm involved i believe you may get an idle undershoot/overshoot. On my gm pcm #411 it has an input called a/c request and this circuit is what i will be using in my ls ac system once my house from hell projects get finished.

[ls1nova71]

The IAC, or DBW throttle body as the case may be, will compensate for any additional load on the engine. I have most of my swaps run this way and have never had any problems with it.

[davepl]

If I understand it, and I'm not sure I do, a trinary switch is a fancy scary way of saying

"A pressure switch with two sets of on/off leads".

The leads are diagonally opposed. What goes in one corner comes out the other corner when the pressure is met.

[Hart_Rod]

Originally Posted by davepl

If I understand it, and I'm not sure I do, a trinary switch is a fancy scary way of saying

"A pressure switch with two sets of on/off leads".

The leads are diagonally opposed. What goes in one corner comes out the other corner when the pressure is met.

High & low pressure safety cutoff switch and a direct signal to turn on E-Fans.