Fans not turning on

[stolnheartdealr]

So my 1.8t will overheat because my coolant fan doesn't run. I found the 60amp fuse below the dash had popped, replaced it but fans still didn't operate. I cut and tested each individual fan which runs when directly connected to the battery but the resistance measured on each fan is only .7 and .8 ohms each which I found odd. I pulled another fan control unit from a junker today and it just popped my 60amp fuse again. Could be I just got another bad one, I've read these units failing is a common b6 issue (btw the one on my 03 is the 600w 8E0959501AG one) so I've just ordered a no name replacement from amazon prime.

I was wondering what everyone else's experiences with failing control units. If yours died on you did it take your 60amp fuse with it like mine did? Has anyone measured the resistance of their fans and is that low value to be expected? 13.5v / .7ohms = ~20a so even while it is a low resistance this alone shouldn't cause a 60 amp fuse to break. I've recently done my timing belt and removed the front end and while I did this I removed my inoperable A/C compressor. Not sure if my A/C compressor left disconnected would cause this but I mention it anyway because I know one fan operates to lower coolant temperatures and the other fan is operated to assist in climate control. I should also mention I have test the operation of the fan relay, I get ~12v at the accessory wire going to the fcu (from what I understand the 4 wires going to the fcu are power/ground/ecu/acc., power and ground are constant however fused 60a, acc is on a relay and fused in the driver side fusebox and the last wire is a pwm signal from the ecu)

[5ktq]

I don't have a wiring diagram handy (does anyone have one? the bentley one floating around the internet is only partial), but low resistance sounds correct to me.

If its a 600W fan, 600W / 14V = 43 amps. 14V / 43A = 0.33 ohms

The leads in your multimeter and contact resistance are higher which is why you get the higher value, so that's not really a good way to test it. I guess you need a low resistance shunt in series with the fan and a car battery, and measure the voltage drop across the shunt. Fan bushings may be dying and causing it to pull >60A.

[stolnheartdealr]

Well that 600w is likely the sum of its output and since it's driving two fans we'd be better off halving the power in your example and the resistance would fall a lot closer to my readings. Multimeters are designed with consideration for lead resistance, battery voltage/current degradation, etc. I have a DC clamp meter though so I can try the fans again tomorrow direct to the battery and get that reading for posterity :D my little meter can only handle 10 or so amps in line so if I'm right about that rating and our guesstimates of these fans nominal current consumption then the clamp meter is my only option.