Stuck on the cooling fan...

[zaphod4239]

I have a 98 SL1 that runs hot, and I'm not sure the cooling fan is turning on (at least my daughter says it's not since she drives it ...). After searching this forum and the how-to's then checking the car, I know:

1. Jumpering the ECTS connector DOES NOT turn on the fan with the key at "run" and there is no voltage at the fan motor plug when checked with a meter.
2. The fan motor works (ran 12 volts directly to it), no blown fuses, and the relay works
3. There is 12 volts at the fan motor plug when checked by grounding the pin on the relay (from the manual fan switch how-to)
4. There is a good ground at the fan motor plug when checked with a meter
5. There is 5 volts at the ECTS connector with the key at "run"
6. The fan does not turn on with the AC (but I'm sure it needs recharging)
7. Resetting the computer (removed the negative cable from the battery) made no difference

I spent most of the day on this, and the info on this forum is great. I DID NOT change the ECTS since I don't think its the problem given #1 above. Any advice?

[eljefino]

Possible you need the motor running with the ects terminals jumpered.

That will trip a fault code for overtemp/shorted wiring but the computer will force the fan on.

Similar should happen if you unplug the ECTS connector.

When you do this, give it a minute to register the fault condition. When the check engine light comes on look for the failsafe fan.

And I would change the ects prophylactically to avoid future trouble potential.

[ssicarman]

Welcome to the board.

Must say that I nave not heard of any one jumping the terminals of the temp sensor connector. Don't know that it would be something that I would do or reccomend.

Did you inspect the connector terminals for ANY signs of corrosion? If there are any then the sensor is no good and needs to be replaced along with the connector.

It looks like you have done a reasonable amount of checking. You do need to remember the the one sensor is responsible for reporting the engine temp the PCM and then that sends the info to the gauge. If the sensor is skewed then the gauge info is also skewed as is the PCM fan turn on point. So basicly you can't trust the temp gauge is you suspect there is a problem.

There are a couple of sure fire ways to check out the PCM temps sensor. One is to use a scan tool that has the ability to isplay the temp readings of the gauge via the PCM and compare that to the readings of a thermostat in the coolant surge tank. The readings should be very close from cold engine start up to the point where the coolant is hot enough to start boiling with out the rad cap on. A five to 10 degree F difference indicates that the sensor is bad.
The other way is to just remove the sensor from the engine and inspect it. If you remove the rad cap from the surge tank and then reinstall it you will not loose a great deal of coolant when you remove the sensor. With the sensor out see if it is a brass or plastic tipped one. If brass then you likely have a problem else where. If plastic tipped then inspect it for cracks, splits or any other visible damage. The plastic should be a uniform colour. If there is discolouration then that is a sign of cracking. Any thing like cracking etc the sensor should be replaced.

For the approximate cost of 20$ it usually is worth just replacing the sensor if you know it has never been done before. If the connector is corrosion free then that should be all you need to replace.

[GreenSC2]

You might want to inspect the ECTS to see if it is the older plastic tipped one. If it is replace it. Jumpering it, not a good idea.

If your ECTS looks like the one on the right, replace it. If it looks like the one in the center with a bulgyer brass area in the middle, it is the newer redesigned type. You can tell the difference without removing it.

[zaphod4239]

Thanks. The ECTS connector was clean, and I'll check the sensor ... likely won't get to it for a few days. As far as jumpering the contacts on the ECTS connector, I followed the instructions from "diagnosing the cooling fan" in Wolfman's how-to guide on this forum:

1. Disconnect the ECTS (Engine Coolant Temperature Sensor) connector.
2. Connect the two contacts inside the connector together with the two ends of a small paper clip.
3. Then turn on the car (either start the engine or turn the key to "RUN" without starting the engine).

The car is running same as before, so I don't believe I shorted out the computer.

[eljefino]

where there's 5 volts at the ECTS connector that says to me it gets regulated voltage and current from a "special place" on the ECM. So a "dead short" won't do anything.

One thing you can do is find a chart of resistance vs temp for the OE ECTS and feed the puter a temp that's high, but plausible, with a resistor. Or what would be really cool would be a potentiometer-- audio taper likely the best range-- hook that up, and twist the knob while watching your dash gauge.

[poorboy]

Have you tried exchanging the relay with a relay that you know works??

[SaturnTech]

OR you could just spend the $15 and replace the sensor that is a known problem on these cars. Have you run the car until the temp got up into the RED to make sure the fan isn't coming on??

BTW-disconnecting the battery cables on a 1996 and newer vehicle does NOTHING for you, other than to reset your radio presets. It will NOT clear a CEL or reset the computer in any way. This is part of the Federally Mandated OBD II software. Unless you really like resetting your stereo presets, leave your battery cables alone.