Cooling Fans won't come on

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Cooling Fans won't come on

September 04, 2006, 06:45:16 PM

After 8 months of work, my gf's 88 TC is FINALLY back together and running. It runs good and will be on the road in a couple weeks. But first I have to work on the typical kinks and quarks. As of now I have taken care of everything except for 2 things. The first is the car overboosts...I have to check the hoses and routing for the hoses. Simple problem. But the problem I have a question on is about the cooling system.

The system pressurizes and doesn't leak, but the coolant temp gauge doesn't move and the fans don't come on. I have replaced the ECT so it isn't that. The passenger side fan comes on when doing a self test, so the PCM is able to control at least one fan. I'm out of ideas. BTW I removed the dumb oil "cooler" and put in a remote mount filter kit. At first I plugged the intake port for coolant and thought that might be the problem. Since then I have run a line around the engine and removed that plug I originally put in. Before with the plug installed, the system wouldn't pressurize. After I opened it up, the coolant hoses get nice and firm. So that took care of one problem but not the other. The car will get nice and hot, but the fans won't come on nor will the temp gauge move. Sometimes though, the gauge will shoot to full HOT! Yet, still no fans. I need some suggestions on what to check. I only get to work on the car on Sundays, so I won't get to try anything for about a week. Any help would benefit me hugely. I just want to give my gf her car that she loves so much back....I'm already 4 months overdue on the project....so I just need to get it back to her. An aftermarket sensing probe kit isn't out of the question either, but I still would like the gauge to work.

Cooling Fans won't come on

Reply #1 – September 04, 2006, 07:26:25 PM

I ended up using an aftermarket fan controller. That would be my suggestion

Cooling Fans won't come on

Reply #2 – September 05, 2006, 08:40:43 PM

I understand your suggestion, and as I have said...I have no problem running such a controller. My gf needs the gauge though. She is lacking in the automotive department and doesn't know the signs of overheating. She'll keep driving until she's home....or stuck. An aftermarket gauge isn't in the cards right now...she has a plan for the car and an aftermarket dash setup is in the works for a later date. For now, the stock gauge is all she has and wants. If someone has an 88 EVTM and could chime in, it would be very helpful. I have an 84 EVTM, but being an 84 doesn't help the "futuristic" 88, haha.

Cooling Fans won't come on

Reply #3 – September 05, 2006, 08:48:04 PM

I was having the same problem...Or atleast I thought I was having a problem.

Cooling Fans won't come on

Reply #4 – September 06, 2006, 10:53:33 PM

well in a T/C there are 3 temp sensor for the water temp. 1st one is for the ECu and it is on the top of the lower intake between 2-3 runners, 2nd is on the bottom side of the lower intake that is for the fans, 3rd is in the block right above the oil cooler that is for the gauge. I've also seen it where the fan controller on is in a water line between the oil cooler and lowser intake.

Cooling Fans won't come on

Reply #5 – September 07, 2006, 12:18:21 AM

This one has the 2nd sensor on the coolant line, but it is right outside of the heater core and not near where the oil cooler was. The one in the block...well we are using a different block...this could very well be the problem, as it is my original 84 block. I'll try to swap it out come this weekend and see what happens. Is there any way to test the fan sensor without running the temp upto 250*?

Cooling Fans won't come on

Reply #6 – September 07, 2006, 09:06:20 AM

I dont think that it being by the heater core would matter. I know the water comes out of the water pump to the heater core then to the oil cooler then to the lower intake. I know that my 84 block has the hole right above the oil cooler/filter spot. I do know that the yellow wire red stripe is the one for the fans temp switch. Also you could take the sensor of and heat it in some water in a pan and see if it grounds out when testing it with a multi meter.

Cooling Fans won't come on

Reply #7 – September 07, 2006, 09:34:47 AM

On an 88TC there are only two coolant sensors. There is the one for the gauge and the ECT. The ECU controls the fans on the 87-88TCs through the IRCM. This is different than the 83-86 TCs which use a separate fan controller and temp switch.

Actually, sounds like to me you have a fan switch inplace of a gauge sender (thus why it shoots to full hot...it hits the temp switch temperature and...boom...the gauge goes full hot). Find the right sender and try that.

The fan issue is probably the IRCM....look into thundergrowl's other post.

Cooling Fans won't come on

Reply #8 – September 07, 2006, 07:22:21 PM

The sensor in the heater hose is for the ATC.

When i say controller, i mean, a controller that turns on with temperature.

Cooling Fans won't come on

Reply #9 – September 07, 2006, 09:30:03 PM

I understand what you meant by a fan controller. I have one on my Cougar, which still overheats with two fans running almost all the time, but that is another story. I'm more worried about the gauge reading. The passenger side fan works when doing the KOEO self-test (had to do that to get the TPS code). Once I get the gauge to work, atleast read temperature, then I'll worry about whether or not the fan is coming on at whatever temperature. If after the gauge starts working and the fans still don't come on before it goes max hot, then I'll get a controller like you were talking about...sorry I didn't elaborate earlier on what I meant by controller.

I will be sure to switch the block unit this weekend and see what happens. Very possible that it is a switch and not a variable resistor. Also that would explain why my engine light would fade in on my 84 before I had an buttstuffog temp gauge.

Cooling Fans won't come on

Reply #10 – September 11, 2006, 08:37:27 PM

Solved! Swapped the 84's switch with the 88's gauge sender and now we have a working temp gauge. Thanks for the help. If I wouldn't have been turned onto the fact that the 84's used that location for a switch, I probably wouldn't have figured it out. And the reason the fan didn't come on...well I'm guess we didn't have it hot enough. So I took it around the back yard a good 10 minutes with some grass drifts and 15 psi runs...that took care of the not enough heat. The car is now 100% done and will be on the road as soon as the plate gets transfered back onto it.

Once we get it broken in, I'll use my newly learned detailing knowledge (the Grand Prix guys over at ClubGP.com are very hardcore on the detailing, they have a specific "Car Care" forum!) and get it ready for some pics.