Fan wiring help: Volkswagen switch + AC/on.

[Fett]

After reading and reading again, I decided that the Rabbit switch would be the easiest and most accurate way to trigger my fan to come on. I plan on doing the install this weekend, and just want to get my ducks in a row.

I searched for this and either didn't find it, or was confused by what I did find. I have relays and the Volkswagen switch, but can't find anything about wiring it up and having a "AC on" switch. I find a lot of diagrams showing the imperial fan controller with a wire for the AC clutch, and I found a diagram showing how to wire with the Volkswagen switch...but that doesn't show an AC clutch wire.

Basically I want to use the Volkswagen switch and relays instead of the Imperial fan controller and relays, but I still want the fan to come on with the AC on.

 

[HISSIN50]

Are you using something like Luke's article as a reference?

If the thermal switch can switch 12 volts (I think his schematic showed it doing just that) then it's easy. You can tap into the wire to the positive side of the AC clutch, and run it to the same terminal on the relay that your VW switch goes to(86 in most folk's diagrams, if they are sticking with conventional nomenclature).
I might add a blocking diode to be real anal if someone envisions feedback to the switch being an issue. I think that might be overkill.

If you're switching ground with the VW switch: you'd have to plumb a second relay for the AC. On the second relay: I'd just have the AC wire at 86, ground at 85, ground at 30 and 87 would be a ground output. I'd run that 87 wire to the same wire on the first relay that your ground from the VW switch goes to (you're only using the second relay to convert the 12 volt A/C-pulse to a ground-pulse that's compatible with your VW switch's polarity).

I'm sorry - that was clear as mud, huh?

 

[Fett]

Yea, that makes sense. So if I am following the diagram shown here:

http://www.mustangmotorsport.com/fan.html

I would just run a wire from the + side of the AC Clutch to the wire going from the temp switch to 86 on the relay. As long as I tap it on that wire somewhere between the switch and the relay, it should work fine. At least that is how I am understanding it. Sounds fairly easy...much easier than using the Imperial, which I have had a lot of people tell me are inaccurate to begin with.

I have the correct tap and am ready to tap the thermostat housing. Hopefully this will go smooth.....but judging from everything else I have done, something will hold me up.

Thank you.

 

[HISSIN50]

That sounds like a plan (we were thinking of the same fan write up - that article's on Luke's site).

Since he indicates that the VW switch is isolated and can pass 12 volts, your idea should work like a charm.

Good luck!