My 89's fans are not coming on properly. I was stuck in gridlocked traffic today:mad and the temp got up to 263:eek: before I could get out of traffic and get some airflow. It was only at the danger zone for less than a minute. When I got home the temp was down to 229 (roughly 5 minutes drive time). I turned the key to the on position and the fan in front of the radiator kicked on but the other one did not. The digital readout was at 253 with the car NOT running. The radiator was recently flushed and filled. I'm running a 160 thermostat and a Hypertech Stage 2 chip. Do I have a bad relay, sensor, or possibly both? :confused:

Fan does not come on when AC turned on.


[Modified by 89ragtop, 7:45 PM 10/4/2001]

 

Main cooling fan is not commin on. Could be Failed fan (did it use to run all the time with that 160* chip?), relay (next to master clyinder), fusable link D (down below battery at jump start junction block).
Could also be ecm temp sensor below throttle body (this would probably set a code, but perhaps not), or ECM or wiring failure.

Try connecting the red / black red wires on the fan relay, fan should run. If it does run than relay is bad. If not than provide +12V and ground directly to fan leads - fan should run; if not than fan is bad.

General circuit: ECM provides ground to main fan relay when temp sensor below throttle body indicates over 220* to ecm or AC high pressure switch indicates AC is on.

Good luck, hope it's the relay.

Pete

 

One of two things have to happen for the ECM to kick on the main fan: A/C pressure switch indicates high side pressure above 233psi (and since this is working on your car, your ECM is at least recognizing this signal and the Fan Relay is working) or the temp sensor reads 226 degrees. As a further test of the ECM, ground the diagnostic connector. The fan should run regardless of temperature. The problem could be in the temp sensor, it's wiring, or ECM. A wiring problem should show up as a Code 14 or 15, so verify that you don't have either code and check the connection at the sensor - it's on the front of the manifold and the wires are yellow and black. Also, the ECM sends out a 5 volt reference signal on the yellow wire which can be verified with a DVM (Sensor disconnected) and that can be used as a further test that the wiring and ECM are good. Finally check the resistance across the sensor. At 70 degrees, it should be 3400 ohms, 100 degrees 1800, 160 degrees 450, and at 210 degrees 185. Readings out of range indicate a faulty sensor. Hope this helps.

 

Good Tips - He did say that the AC did NOT kick the fan on, it was the Aux fan that came on which is whole different circuit.

The ALDL tip is a good check.

 

No fan when ALDL is engaged. No codes other than 12. I get 11.2V to the realy with key on and 9.6 from the fan cooling switch. Checked across the relay and he fan engaged for about a second and then blew the 10A fuse for the ECM. Any other thoughts? :confused:

 

Have you taken the radiator out and cleaned it lately ?? I found a pile of junk after just 2 years and it dropped my temp down 30 and it rare to go over 220
now , but I have both fans running all the time.

 

There is no main fan cooling switch, just the coolant temp sender and a/c pressure switch. Here's what the Shop Manual says to do when grounding the diagnostic connector doesn't turn on the fan: Disconnect the relay and with the ignition on, probe D (dark blue) and E (red) with a test light to ground. If the light is off on either circuit, the wire is open or shorted to ground, so you need to repair the circuit. If both circuits lighted the test light: ground the diagnostic terminal and probe the dark green/white wire with a test light connected to 12 volts. This is the signal wire from the ECM which completes the circuit to energize the relay and thus, turn on the fan. It should be sending the signal because you've grounded the diagnostic connector. You're checking to see if it's open or shorted to voltage which will be the case if the light is off. It might also be, if the light is off, that there is a faulty connection at the ECM or the ECM is bad. To verify continuity of the wire, you're going to have to check resistance from the relay terminal to the ECM (Pin C1). Never check resistance with the ECM connected. If the wire is good, it's the ECM. If the test light came on, then jumper the black/pink wire to the red wire and the fan should run indicating that the relay is bad. What you're done is verify that you have voltage inputs up to the relay and that the ECM is supplying the ground to energize the relay which makes the fan run. If all of the circuitry up to the relay is good and jumpering the black/pink wire to the red wire did not turn on the fan, then the problem is in the fan motor or the wiring from the relay to the motor. If this is the case, leave the red and black pink wires jumpered and disconnect the fan. Put a test light across the harness terminals and if it lights, it's the motor. If it doesn't light, probe each terminal with a test light to ground. A light on one indicates a bad ground which is the black wire out of the motor to the front cross member. If the light is off on both terminals, then the powerwire (black/pink) from the relay to the motor is open. Hope this helps a little more. Dollars to donuts its the #$@! Relay!

 

Jes-Oh-Flip!

 

Forget the aux fan switch - has nothing to do with your problem.

I could write a long post - but think you should replace the main fan relay (the one near the master cylinder) and let us know what your find. I really believe this is the best course right now.

 

PeteL- Thanks for your help. The red wire is dead. Where does the other end go? I checked it at the relay connector and a little further down actually into the wire. No light on the test probe. The green one is good. Looks like my problem is the red wire circuit. I don't have a good wiring diagram on the car to tell me where the other end goes. It looks like it leads somewhere to a relay or terminal bank behind the battery. Thanks for your help to this point. I'm getting closer.