Quote:
Originally Posted by JustJeff
Sounds like I might have assumed too much. I assumed difference between 2 wire and 3 wire Taurus fans was that 2 wire was 1 speed and 3 wire was 2 speed. I also assumed that for my 3 wire fan that I had one common ground and 2 different +. + for low and + for high. I assumed that the diagram was for either high or low, but not for both. I physically swap wires to go from high to low. I never have all 3 wires connected at one time. I also assumed the ground was common (to engine, chasis, etc), but I don't really understand floating grounds. I've done some light reading and so far it escapes me. My best understanding of floating grounds are car speakers. Each speaker is not grounded to the chasis. They are grounded via the amp.
It's been a while since the car has been sitting and I wired in the fan and relay. I'll let you know where the fan is grounded a little later today/tonight...after I dig into the wiring.
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Found this Taurus e-fan wiring diagram with a little googling on a DSM forum
If this diagram is correct, the fan body provides the ground (-) return, and there are 2 other wires - a high & low speed (+). Here it's rigged up so that whenever the switched +12V is on, and the "temp probe switch" is closed, the fan runs at low speed, and when the "AC Clutch wire" is providing +12V, that 2nd relay switches the fan to high speed. Note also they mention the high current draw when the fan starts up on high, and they recommend using a 75A relay, and the fuse to the battery is a 50-70A, and "normal" current draw on high speed is ~34A! Sounds like an alternator upgrade will be in order if you still have a stock FC alternator in there.