MSefi.com read only forum (Jan.15,2018)

Hey all,

I have chosen to retain my stock A/C and was wondering how I need to wire up my second fan so that it turns on when the A/C is on. My stock computer used to control this.

I suppose I could have that second fan on a switch and whenever I turn on the A/C to make sure I flip that switch, but i'd rather it be all intregrated.

I tried searching but didn't find anything. Any ideas?

I have MSII

Just thinking out loud here..........

Why not use the signal that is sent to the compressor clutch already to turn on fan #2 when the compressor kicks on.
And save the MS output for something else?

Ken

I'd take a similar approach to KJones. Use a relay to turn on the fan whenever the A/C is on.

I thought about having the fan turn on when the A/C is on. The issue is I have no idea how to do that. Also, the factory computer told the fans to turn on when the pressure hit a certain level.

The A/C has 3 wires coming out of it. Two go to the fuse box and the other goes to the A/C switch on the dash. A friend told me that the two that go to the fuse box are a high and low pressure switch. I am not sure what that means but that still doesn't help me to understand how to wire the fan (which is a simple power and ground) and have it turn on when the A/C is on.

If it was me, I would locate the wire that goes to the compressor clutch and attach the relay coil to that wire and ground. From there you could run 12 volts to the fan via the N/O relay contacts.

Ken

kjones6039 wrote:If it was me, I would locate the wire that goes to the compressor clutch and attach the relay coil to that wire and ground. From there you could run 12 volts to the fan via the N/O relay contacts.

Ken

The compressor tends to cycle. It would be better to simply have the fan run all the time the AC is switched on.

Point well taken Dave!

kjones6039 wrote:Point well taken Dave!

Of course if it is an upmarket car with multiplexed switching, it may not so simple. ;-)

It's a 1998 Dodge Avenger ES.

I suppose it's one of those things I really can't rest unless the engine is running huh.

My 92 Dakota has a push button to turn on the A/C I just wired in a relay to light thats lit when the button is in to work my fan.
Just an idea