coolant fan ?

[nuc]

My coolant fan all of a sudden does not turn on when the motor reaches its normal turn on temp. It will not turn on at all, unless I turn on the A/C system, which is what I have been having to do to cool the car down.

Anyone with an idea?

Thanks

 

[malibuick231]

you may check the relays on the driver side fender or ground the wire off the coolant sencer if the fan comes on the sencer would be bad i would think

 

[Darkside]

I had that problem with an 88 IROC I use to own. I took a screw driver and wacked my relays with the handle and the fan worked. I then went and replaced the defective relay.

 

[salvageV6]

Low speed fan relay most likely. I would do the screwdriver trick only use a rap not a whack.

Save the whack for when the rap don't work.

Car must be warmed up over the 160 or so mark for the ECM to command low speed operation. Assuming aftermarket decent chip.

Or you can ground the green trigger wire and tap until it kicks on.

Swapping the two small relays should get the low speed operation going sacrificing the high speed operation. Also a good relay test.

 

[nuc]

One thing I forgot to mention was that a past owner took out the low speed relay that attaches to the fan so that it only runs on high, when it runs!

I'll try out rapping the relay on the drivers side fender and also grounding the coolant fan sensor to see what that does.

Thanks

By the way, which of the relays on the drivers fender would it be?

 

[nuc]

Well, I replaced the fan relay switch (GM) and rapped on the relays on the drivers side fender and the fan still doesn't turn on. However, if I ground the wire to the fan switch the fan does turn on. Also the fan comes on when the A/C is on.

Any ideas on what I should do next?

Thanks

 

[salvageV6]

Check the low speed relay and ECM wiring and chip parameters and the big resistor near the fan and its wiring.

 

[machinegun]

NUC, look for the sensor front drivers side intake with one green wire going to it. Disconnect this and using a jumper wire ground this. If the fan comes on then the relays and all wiring are OK. The switch or sensor itself is bad. Easy to replace and cheap at any discount auto parts store.

 

[nuc]

Sorry folks, I was writing this in an unclear way.

Today I replaced the fan switch (sensor) with GM. When I ground the green wire that goes to it, the fan turns on. However, the fan doesn't turn on when the car reaches the temp that it should be turning on. Rapping on the relays doesn't help.

The fan does turn on when I shut off the car and the temp is ~170-190 (does not run when car is on ). It runs a couple of minutes and then turns off.

There is no low speed relay on the fan itself, it was taken off by a previous owner, so it only runs on high.

Sorry for the confusion.

What am I doing wrong.?

Thanks

 

[nuc]

Could having wrapped the threads of the fan switch with teflon tape for leaks be causing it not to ground the green wire and turn on the fan?

 

[ChrisF]

Exactly, sounds like you have no ground.

 

[dpok69]

I had a similiar problem to what you are describing. What i did was ground the wire by the fan relay (forgot what color, but can be accessed through Gnttypeorg), the fan should turn on. Somehow i was trouble shooting with this wire grounded. I think even though this wire was grounded sometime the fan would not turn on.

It turned out that there is a fan ground also by the rear of the passenger side valve covers. I was messing around with those bunch of wires back there and suddenly the fan kicked on. I used to have bad motor mounts, and this tore the ground wire a little. Sometimes it would make a connection sumtimes it would lose it. This explains why when you shut off the car the fan sumtimes works cause the engine moves a little and makes the ground.

In my situation, sumtimes the fan would be on while car is running sumtimes it would not. i ended up cutting the wire off the harness and grounding it to the back of the firewall and after that had no problems. My digital dash goes buggy sumtimes too. Guess what? It's grounded in the same area.

 

[salvageV6]

I'd swap the two small relays and do the same tests with grounding and A/C and driving the car up to 170 degrees.

If the fan works while driving you have one bad small relay.

The thing missing up front on the fan assembly is a power resistor not a relay. Just so it's clear for ya.