Is one of the cooling fans to run when the car is cold and the key is turned on?
As I recall, this should not happen. I have run a search on this issue and have run all of the suggested test. Every thing checks out withe the exception of the tranmission sensor of which I can't get any resistance. I have switched out the sensor with the one that was in the car before the fire and still no resistance. I have run a continuity test from the transmission to the control module at the passenger seat and have not had any opens. The fan that runs is on the drivers side, although the WSM indidcates by the wiring color should be on the passenger side. The fan also runs at high speed. This fan runs with the AC switch on and off and with the hood open.
Additional info, their are no fluids in the engine or transaxle. The dashboard wiring harness was repaired after a cat fire, the engine harness was replaced, the engine was pulled and rebuilt.
As always any thoughts are greatly appreciated.
Thanks, Terry

 

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There is no reason for the fan to run when the car is cold.


The trans switch should show infinite resistance (open circuit) when the trans is not overheated. Verify the wiring and function by connecting the two conductors together at the trans switch, and verify that the resistance goes to zero when you connect the switch wire to ground (see coordinate P35 on sheet 5 of the WSM wiring diagram for that switch and wiring). If the wire shows continuity to ground with the switch disconnected, you stuill have a wiring fault from your fire.

The wire runs from the switch through terminal S25 on the main electric panel, then immediately back out of the panel at N23 to terminal 9 on the fan controller by the passenger seat. This wire is common with the intake temp switch on top of the intake manifold, by the way. Pull the wires from that intake switch to make sure you are testing only one thing at a time. I had to put in a new intake switch after I gave the engine a bath once; If you used water to clean the engine it's possible that your switch has the same intermittent-close problem that I had. Pull the wiries off to be sure.

The AC switch should be off for your testing. The hood switch is 'fail safe' so that it's closed when the hood is open. If the switch or wiring fail, the circuit is open and the fans are allowed to run. There's also a connection from the that same hood switch through the alarm module to the anti-theft connection on the radio. If the radio is removed and that radio bucket theft wire goes to ground, thae fans may not run. This isn't your problem, just mentioning it since you had the dash wiring replaced.

The fans get power directly from the battery, through dedicated fuses 28 and 29, through a pair of dedicated power leads that attach to the positive battery terminals. Two recent fan-failure problems have been caused by loose connections at the battery. With your undercar fire, these wires may have been damaged as well. To diagnose, you'll need to be able to verify that there is voltage passing through fuses 28 and 29 while the fans are trying to run. Make a tap fuse with a couple lengths of wire and some spade terminals so you can connect a fuse at the ends of the wires and plug it in to 28 or 29 to test. Verify that you have full voltage available on both sides of the fuse while the fans are trying to run. If you see low or no voltage, look for a wiring problem between the fuse panel and the battery on those two dedicated red wires.


Look also at the temp sensor at the front of the radiator, low on the driver side. If the circuit to this sensor is open, the fans will run immediately on key on. Compare this with the trans and intake temp switches which will run the fans regardless of key position. The sensor is a reverse-coefficient thermistor, so an open or low resistance on that sensor loop indicates that the engine is hot. You can see and reach the connector down in that bottom front driver's side corner of the radiator, around/under the AC condenser. test the resistance of that circuit ithyour ohm meter from terminal 1 on the control unit, measured to ground. You may need to clean the connections at the MP-II ground point, which is adjacent to the jump-start terminal on the pass side inner fender panel. Look for a lot of brown wires converging. (hard to see, up under the fender mounting lip)

HTH!

 

If the temp sensor at the lower driver side front corner of the radiator is disconnected/broken, one fan will run as you are describing. You can see and get to this at the front of the radiator from above.

 

Bob, Thank you for your detailed response. I will start going through the items that you have discussed tomorrow and I will let you know how it goes. Since my last post I have found some additional problems which I am sorting out and correcting.
Bill, Thank you for your post. I have the temp sensor out and will recheck it. Also after reading the posts from SF I noticed that you met my son Kevin.