I have a 92 RS with a V6 engine and 5 speed transmission. I noticed that when the car is stationary or I am stuck in traffic, the engine temperature will just climb but the fan will not engage. I did some tests in my driveway and yes, the fan will not turn on when the car is stationary. The moment, I put the car in gear and start moving (even slowly) the fan kicks in. Is this normal? Looking at the temperature gauge, I don't think so and the temperature reading worries me. I have already changed both coolant temperature sensors but that didn't do anything.

Here is what the gauges look like when the car was idling in my driveway for about 10-15 mins. I know my idling RPMs are a bit high but so far, I haven't found why is it like that.

 

That fan situation is odd and wrong...I do not know anything about late v6 fan control. Check the RPM with another tach- the ,90 up tachs often read high when they get old- a resistor or other part degrades and can be replaced to correct the wrong reading.

 

The fan should be moving when idling in park if coolant temp is appropriate, it only makes sense. are you certain its not just wind causing the fan to spin? if its a matter if being in gear, then the fan should start moving even with the car still, brake applied once you put it in drive.

 

I don't think it was a wind that was moving the fan. I only drove like a couple of feet down my driveway (towards the garage so no direct wind into the front of the car). The fan will not go on when in gear. Only when the car is in motion. Any ideas on what to check next?

Also, any pointers on how to measure the RPMs outside of the tach that's built into the gauge cluster? I am waiting on a small board that will allow me to build a sort of DIY OBD1 scanner. Not sure if that's going to allow me to measure RPMs though.

 

gonna go out on a limb, that it is impossible for fan to start turning only because your wheels are moving.

 

It does sound weird. I agree. But I had my son observing the fan couple of times and that's what the car is doing. Hood up, I am driving the car on the driveway a couple of feet and the fan starts. When stationary, I can have the car idling for 15 minutes until the temp gauge goes almost to the red and the fan will never turn on.

 

Then in that case, my conclusion is the fan is not getting enough amps, and when you get the alt flowing, the amps flow, thus the fan flows. how bout that????

 

If this was an alternator issue, then wouldn't revving up when stationary produce the same effect as driving? Wouldn't the fan turn on when I rev up even if not in gear? The car was sitting for about 10 years and I just got it running. It is possible that the alternator is weak but the battery never goes down and I can always start the car. Lights work fine when the engine is running.

 

Rather than watching the fan, maybe hook a test light up to the connector and monitor for voltage when you start moving just to ensure you're not seeing air pressure

 

I kinda recall the late v6s control the fan by the ecm monitoring coolant temp via the CTS and also A/C pressure switches

 

Good point, I'm out of ideas.....

 

"It does sound weird. I agree. But I had my son observing the fan couple of times and that's what the car is doing. Hood up, I am driving the car on the driveway a couple of feet and the fan starts. When stationary, I can have the car idling for 15 minutes until the temp gauge goes almost to the red and the fan will never turn on."

Dont take this the wrong way.. but how old is your son? Sometimes kid see movement and say" the fan is moving:" so iwouldnt really trust what he says. the best thing to do would be to jack the car up and support it securely on jackstands, put it in gear, have your wife / a friend in the seat to make sure she can shut it off if something goes wrong and look at the fan.


Its very possible that moving can cause a little air flow to cause the blade to turn... youd also HEAR the fan if it was coming on. The V6 single fans are rather loud...


you could have a bad fan motor... does it come on when the ac is on?

3.1s use the engine CTS to control the fan for coolant temo operation where as 2.8s used the fan switch on the back of the passenger side head.

 

I know this may be like apples to oranges but on my j-car single fan...yeah with the a/c on the fan comes on. Also...there was a "dumb" switch that turned the fan on at some deranged temperature like 235dF but it was there in the event that the ECM failed to turn the fan on. The picture of your gauges seems a bit high, are you experiencing any boil overs?

I had another vehicle that exhibited just the opposite...luckily I was able to hook up a scanner, watching the temperature never exceeding 185dF and the coolant started boiling over. This one was due to a faulty temperature sensor.

 

Thanks for all the replies. I did some additional testing. With the paper clip in the OBD port, the fan turns on and runs. So that should rule out relay, wiring, fan motor, grounds and ECU, correct? I did also ground the green wire from the relay and the fan turned on. With the car stationary, the temperature just climbs and the fan never turns on. I also replaced the CTS (both actually but I know one is only for the gauge) with original GM/ACDelco sensors. Still no good. I did wire a temporary fan switch that grounds the green wire so I can turn the fan on manually. With this switch, when the fan is on, the temperatures stay around 220. Right now, all points to the CTS or the wiring between the CTS and ECU. Most likely the wiring since the CTS is brand new. Does anybody have a schematic where the wires from the CTS by the thermostat go so I can check the continuity?

 

I would assume the cts is giving a reading i didn’t see a mention of code 15.
you can ohm the cts and refer to this chart to see coolant temperature if you don’t have a scanner. Primary fan will kick on at 226.4 based on the computers calibration chips setting BAWX chip code.

 

If you unplug the cts and jumper with 100 ohm resistor the fan should come on .

 

Will try that today.

 

So as soon as I unplug the connector from the CTS by the thermostat (with two wires) and start the engine, the fan starts working. Obviously, with this, jumping with a resistor doesn't do anything since the fan is already running. I am assuming that it is the CTS that's bad, correct? That unless my temp gauge is way off but I never really heard the fan turning on even in a stop and go traffic when temps outside were around 80F.

I am waiting on a part that will allow me to build an OBD1 scanner so hopefully this will give me some more info. There are no codes stored in the memory when the paper clip is used.

 

An update: I flushed the coolant system, put new coolant, changed the termostat to 180F and the car runs cooler now. I think I had an air pocket as I put more coolant than I flushed out. When in traffic and with the fan running, the gauge stays a hair before the 220F mark when the outside temp is at or above 80F. With highway driving I am at about 200F (according to the gauge). The fan still doesn't turn on unless either the A/C is on or I manually jump the ground wire (I did install a switch in the cabin for that).

 

3.1 has a ECM controlled fan. Did you change out the CTS? If i recall, it uses that 2 wire sensor for both fuel injection and also fan temp. the 2.8 uses a fan swith in the back of the passenger head which is a nightmare to get to.....


If for whatever reason that ecm control no longer works, I think I would personally install a fan switch (like the 2.8s) to take out the possible chance of forgetting to turn the fan on manually and smoking the motor.