97 3.1 Lumina Has Issues

Overheats when idling, fans do not turn on. Replaced temp sensor, checked fuse, replaced relay. Put power to fans, they work. Help running out of guesses!

Welcome to the forum!

Do you have a coil trigger to the cooling fan relay? Do the fans run when the A/C or defroster is turned on?

You should consider moving this thread to the Lumina forum as there may be common issues that cause these symptoms. This forum is more for questions like, "What inputs does a PCM typically use to determine cooling fan operation is needed" but not so much for questions specific to a certain model of car. That's what the model-specific forums are for.

-Rod

Thanks for response! But coil trigger is beyond my abilitys. Where would I find it and what would I do with it? Fan will not turn on with A/C, havent seen fans move other than putting power to them.

You would find the trigger for the coil at the relay panel where you replaced the relay. If you pull out the relay, you should have battery voltage across terminals 85 and 86 of the relay when the relay is told to close. You also should have battery voltage to terminal 87 at all times.

-Rod

Thanks again Rod, cant believe someone is taken time to help me!
Have juice at 87, hear one of the fan Cont. relay click in other fuse block while testing this. No juice accross 85&86, tried turning on a/c and everything, no juice ever! Thanks again Todd

Sounds like you are not getting a trigger to the fan control relay. I don't have a wiring diagram for your car in front of me. Often the relay coils are tied through a fuse to the battery and the PCM controls the ground to the other half the relay coil. So to close the relay, the PCM would provide a ground to the relay coil. You may have another fuse for the relay that is open or you may have an issue with the ground for the relay.

I'll try to find a wiring diagram this evening and see if there's something that jumps out.

-Rod

Wow, the wiring diagram would imply there are 3 fan control relays for your car. There's a 30A maxi fuse in the Underhood Electrical Center #1 that provides power to the contacts for 2 of the 3 fan relays. The third relay contacts get battery power from a 25A fuse in Underhood Electrical Center #2. The PCM controls the relays by providing a ground to the relay coils.

From my quick look, it appears that the three relays are used to provide low or high speed operation of the fans by either running both fans in series (low speed operation) or both fans in parallel (high speed operation). I don't see a single point failure that would prevent either fan from being able to run except in the case that one of the fans has an open circuit and the relays were configured for series operation. Even in this situation though, as the vehicle continued to warm up, the PCM should command high speed operation and one of the fans would operate. If you had at least one fan motor (minimum Fan #2) that is open circuit and at least one relay (minimum Relay #2) that are bad, you could get a situation where neither fan would run though.

Are you sure you replaced the temp sensor for the PCM and not just the temp sender for the instrumentation?

-Rod

Wow! Um!? I replaced sensor located basically hooked to the thermostat housing, I guess assumed it was for the fans. Wouldnt know where to find other sensor. Did not look for other fuse, just the one in the #2Box a 25amp. And checked main fuse panel located in the car. The car is gone for the day, girl off to college. Will investigat more tonite. Thanks Again

Ok, Checked all fuses i could find, no bad ones. Noticed something strange, to me! I have voltage to both wires on my fans, assumed one would be ground. One fan has alot of voltage to them, the other less but is in both.
How can I have juice to them, yet they dont work unless I put voltage to them!? Now more confused than ever! :confused:

Based on your description, you have an open ground somewhere in the circuit. In the low speed configuration, the fans are wired in series. A good motor will have low resistance across its two terminals, so if they are in series and battery voltage is applied to the positive terminal of fan #1 but ground is not applied to the negative terminal of fan #2, you will see battery voltage on all four motor terminals (back probed) with respect to a good ground, but yet the fans won't run.

When you are measuring voltage to both wires on your fans, is that back probing the connectors or unplugging the fans and measuring the wires that would normally plug in to the fans?

-Rod

I am back probing fan connectors. May seem crued to a professional like yourself, but my thought is, cut ground wires to fans and give them a new ground!? Looking for an open ground, sounds like an impossible mission for a shade tree like myself. Again, cant Thank you enuff! Todd

I'm not a professional in the automotive field, but I'd still want to understand what failed in case it relates to other circuits that you're not yet aware of.

What you could try though to determine if this is the problem would be to run a temporary jumper wire to ground to see if that allows the fans to work as expected.

You may be able to find the cooling fan wiring diagram from the "Repair Information" section of the Autozone website. If not, you can send me a private message with an e-mail address that can accept PDF attachments and I'll send you the wiring diagram I've been referencing.

-Rod

As you description above ,you put power to fan ,it work well.I think we can conside about the problem it two ways ,one is the senior didn't send the hight temperature signal to the PCM. The second is the PCM didn't tell the relay to close or the relay can't close. In your description you your replaced temp sensor , check fuse, repalce relay .the only thing l can image is the wire.Maybe the wire break.Check your wire with multimeter,you may find the reason.
It is what l can consider,hope it will help you.

Today-Saturday! Raining hard probly wont get to check anything today. Last night ran temporary ground to fan ground wire, no good! Gonna look for wire diagram today while raining. Thanks again for all the help! Todd

With the temporary ground wire installed, did you backprobe the fan connectors checking for voltage? You could possibly have two issues here, a bad ground to the fans and a corroded connection in the supply wire to the fans. The corroded supply wire could allow your high impedance multimeter to register voltage potential (12V), however the corrosion would so severely limit the current capacity that the fans wouldn't run. You'd only see this though if the ground was open. Otherwise a good ground would sink that low current to ground but the fans still wouldn't run. So if you no longer measure 12V on the fan wires with the known good ground, then remove the known good ground and you see battery voltage again, you probably need to start looking for a weak connection/wire that supplies current to the relays.

Again, you should search the Lumina forum for this problem. If this is a common problem, you maybe could have had this fixed by now.

-Rod

Monday- Only good news, its getting colder outside,might not need those damn fans!! Spent weekend reading Lumina post, one similar but got me no where. Have print of wiring, may take time to figure out what im looking at. Did learn that I replaced the right sensor for the fan. So I am going to start looking for a bad wire, ground etc. Thanks again for all the help! Todd