danbrazda

One of my WS6's cooling fans kicks on randomly when the car is not running. It killed my battery once and so right now I pulled the #2 fan relay to keep it off at all times until I figure out the problem. It is the fan on the passenger side (if that makes a difference). I don't see any issues with the wiring going to the fan at first glance. What else could be causing this?

GMtechmatt

pcm controls fans may be a problem with the pcm

danbrazda

I was hoping for something simple like the relay just being bad. Is it worth just replacing the one for that fan or would a bad relay simply not allow the fan to turn on at all rather than randomly turning it on while the car is off without the key even being in it (what it has been doing)?

danbrazda

I replaced the #2 fan relay and the problem hasn't happen since. If the issue rears its ugly head again I'll update this in case anyone else has the same problem.

danbrazda

I posted too soon- problem is back. Guess I'll see if it is throwing any codes...

RARON455

iTrader: (35)

First, are you sure that both fans are coming on when the car heats up. If its only the passenger side fan then causing grief, that helps, the fans are set up in series for low speed and then change over to a parallel setup when high speed is needed. If indeed only the passenger side fan is on there are only a few scenarios that can cause this, that fan only has 2 wires going to it, so we have to see where the power is coming from. since the system uses both a low speed (series) and high speed (parallel) the passenger side fan can actually be turned on by two different relays, relay 2 and 3. However since only the one fan is spinning that will eliminate the possibility of relay 3 being the culprit because the power coming from that one is shared with fan one, Meaning they would both be on. That leaves relay 2 which can supply just the right fan. Now the question is how, it could be that the internal contacts are bad, meaning that the power could arc across and turn the fan on. OR another cause could be that you have an intermmitant short to that relay that switches the relay, (turns it on) I am not sure which relay you changed, but I would replace the cooling fan 2 relay, and if that does not solve it, then you need to get a meter and OHM the wire that comes from the ECM to relay 2 and 3 (in the drawing it would be wire 473), and make sure it is not grounded out against the car somewhere. THE PCM will let the fans stay on after the ignition is off if the car is still warm, but when it does that they stay in series (low speed) meaning both fans are turning, Since only the right fan is turning I dont think that is happening. I have fought this fight and won, so You hopefully you can benefit from what I learned. Here is a diagram from MY GM manual that I color coded. Mine is a 98 so your wire numbers might be a little different. But they work all the same. Hope this helps, Ronnie
to help you here is the way I colored the wires
Red: (pinkish in drawing) thats the constant 12v
Orange: thats the 12v for the coils of all the relays
green: ground from ECM for low speed of fans (SERIES)
blue: the ground from the ECM for HIGH speed of fans (parallel)
black: chassis ground.
sorry didnt have the exact colored markers, used what I had.

danbrazda

Wow- thanks so much Raron455. The latest is I replaced the #2 relay only and it is still doing it so that leaves a short somewhere between the ECM and that relay. I'm looking forward to tracking down this Gremlin thanks to you

I'll repost when I find the bugger. As another clue to the mystery I was able to get that fan to turn on a while ago by simply jacking up the passenger side of the car- then when I let it down it turned off...hmm...