kraabel

I've been working through some electrical issues and decided to re-wire my axillary cooling fans, since one of the wires had been cut by one of the belts. Now it's a matter of figuring out where everything goes.

I've attached a few photos. It appears that the PO had a relay installed. I'm not sure what it does completely, but what they've done is:

1. Run 2 ground wires from the top of the engine.
2. Splice into the line leading down driver's side fan.
3. Run a separate set of lines down from the relay to the passenger side fans.
4. Put a fuse from the charge post to the relay.

So, my questions are simple: from the relay diagram, which wires go where? I assume one of the posts comes in from the positive terminal. One goes down to the passenger fan, one goes down to the slice into the driver's side and one from the ground point.

There were two ground wires before off the engine, but one of them melted off and I'm not sure where it went, if anywhere at all.

Thoughts?

Tails

From your photographs can we assume that your are referring to your 1990 S4 Auto?

Do you have a set of electrical drawing for your S4?

Is your car still fitted with the flaps and are they working oe have they been disconnected?

My suggestion is that you return wiring to original by making repairs as required to original wiring and circuits.

Do you have a set of Jim Morehouses Technical CDs or do you have a set of WSM? You will need these to carry out fault finding and consequent rectification to get the system back to original.

Tails 1990 928S4 Auto.

Richter12x2

If you want to keep the aftermarket relay, Big Hot 12v (high amp from jumper post?) goes on 36, and fan + on 87. 86 goes to ground, and then whenever you put 12 volts (low amperage, like a toggle switch) to 85, it turns the fan on.

Richter12x2

Also, after that fan's been running a few minutes, feel that fused wire going to 35. If it's HOT to the touch, it might not be thick enough. 87 to the fan would need to be just as big. I'm not sure how much the little factory fans draw (less than 30 amps, apparently) but I'd probably feel better with a 10 or 8 gauge wire on there.

UncleMaz

As described above:

Richter12x2

Exactly, with the benefit of adding a thermostat switch. I just replaced the clutch fan in mine with an electric fan, and I chose to run what's depicted on the left. That way, like a turbo-timer, if the engine is hot, the fan will run even if the car is turned off, until the temperature drops and the thermostat disconnects the fan.

kraabel

The only issue now is that it's got duel fans running. Or rather, I think I understand it in theory, but does the relay power both fans, or just one of them? Seems like the driver's side is still on the main wiring harness. Or maybe I just didn't track the wires down properly.

Richter12x2

That sounds like a good thing, I'm not sure I understand. Also, FWIW, if you get some appropriately sized heat shrink and cover those blue plastic terminals, and move the ground wires to the radiator hold down instead of the front of the engine, it will look a lot less ghetto.

UncleMaz

+1 For reference, I have my stock 944 fans wired as on the diagram on the left for 5.5 years with no issues. Keeps the AX/track days/heavy summer traffic heat soak away. Even on the hottest days, the fan only stays on for no more than a minute. If your battery is good and charged, it is never an issue.