streetzlegend

iTrader: (8)

Sup guys, so was doing a few WOT runs, car overheated and thought I blew a head gasket, got home before it overheated to its death. Turns out my fans werent on! AC dosnt turn them on either, manually grounded the ran wire at the ECU, still no fans on. However when I apply power to them directly they work. So something in the cars electrical system is not happy. Fuses are all good, I can also hear a relay click when i ground the fan wire at the ECU. Can it be a relay?

f550maranello2

iTrader: (2)

could be.. swap the relay with another one in the junction box.. or ohm out the coil on it.. i think the coil is between pin 1 and 2

DennisMik

iTrader: (2)

when you turn on the a/c, ECU pin 14 goes to 0 volts and energizes Fan Relay1 and it sends power to both fan motors for low speed. The power to the fans comes through 30 amp underhood fuse D.

When the engine water temperature get up to 210 degrees, ECU pin 13 goes to 0 volts and energizes Fan Relay2 and Fan Relay3 to run the fans at hight speed. The power for this comes through 30 amp underhood fuse E.

The power to energize all 3 fan relays comes from 10 amp under dash fuse 17.

Fan Relay2 and Fan Relay3 are the same part. Fan Relay1 is different.

streetzlegend

iTrader: (8)

Thank you very much for the information, very helpful. I discovered that both 30amp fuses were burnt. Put a new one i had laying around, as soon as I plugged the fan plug to the fan it burnt again. I think I know the issue, the fans I am using right now are 2001, so I hooked up a 97 fan motor I had around and turned on without setting off the fuse. Right now im trying to figure out on the FSM's how both 97 and 01 differ within the motor.

streetzlegend

iTrader: (8)

Looks like 01 fans use 15A under the steering column, and 40A in the engine bay for fuses. 4th gen use 10A and 30A. So hopefully thats the problem, going to change them and see how it goes. Should fix it

DennisMik

iTrader: (2)

I was under the impression that the 4th & 5th gen fans were the same physical motor. But the connectors are wired differently, causing a reverse of hi & lo speeds.

.......... 4th gen .... 5th gen
pin 1 - lo speed + . hi speed +
pin 2 - hi speed + . lo speed +
pin 3 - hi speed - . lo speed -
pin 4 - lo speed - . hi speed -

Maybe the 5th gen fan motors use more power, I don't know.

streetzlegend

iTrader: (8)

Yeah, im wondering if I should swap the hi and lo wires. I think they do use more power, probably why they require 10 more amps in the fusible links

streetzlegend

iTrader: (8)

So I put 40amp fusible links and they also broke. relays work. I hook up the old fan and works. So as a temp fix I wired my fan controler (relay with a probe) to the 12v high pin of the fans and to come on at 180ish. Also put a 40amp fusible link on it. Basically bypassed the whole cars fan control and did my own. after driving for a bit that 40amp link broke! car started to get hot. I pull over and notice the link broken but also the passanger side fan is stuck! Now I am not sure if the 4th gen wiring caused this, or if its just a freak accidient that the fan is no good (ebay). The only difference like mentioned above is that the high and low 12v pins are swapped on the 5th gen motor. but that shouldnt have caused any issues. what do you guys think?

DennisMik

iTrader: (2)

If the fuses keep blowing, you either have bad fan motors or your wiring harness has gotten damaged and is shorting to the chasis somewhere.

As far as the hi and low speeds being reversed, that shouldn't cause any problem. Another difference in the fan wiring between 4th and 5th gens is that on the 4th gen, both fans get power from fuse D for low speed and hi speed uses fuse E. On the 5th gen, the fans don't share fuses, they each have their own fuse. This could mean that IF the 5th gen fan motor uses more power than a 4th gen fan, then two 5th gen fans might use more that 40 amps combined. I hate to say to try 50 amp fuses because the wires in the harness might be too small to carry that much current.

I think that maybe the safest thing to do is see if you can get a pair of 4th gen fans from the junkyard. In the meantime, you could leave one of the fans unplugged and see what happens.

streetzlegend

iTrader: (8)

yeah, im going with 4th gen fans. the 2nd 01 motor seized as well. So yeah...