Radiator fans will not run unless AC is on

[Buckeye Chuck]

My 2004 Malibu Classic (Old 97-2003 body) has started over heating. There are dual electric fans to cool the radiator and AC condenser. Neither fan wants to run unless I set tge AC to run. There are a total of three relays that control the fans. I have tested them and replaced them with exact matches from a junkyard. I realize this not the same as new relays but the left and right relays are 4 legs and are identical. The 3rd relay has 5 legs and some how runs both fans maybe at low speed? Any way I jumped the LH relay and the fan runs, but when I plug in the relay it does not run the fan? Any ideas???

[maxwedge]

The pcm is set to turn the fans on at any temp over approximately 225. A scan will look at the temps to see if they come on, based on temp sensor input.

[Buckeye Chuck]

That sure seems like a high temperature for the fans to come on. I had an incident with the car overheating. I found a crack in the coolant reservoir and replaced it. I thought that was the end of it, but after driving 15 miles without issue until I stopped to speak to a neighbor and let the car ide while I talked out the car window...within a few minutes it started to spit water and dream from the overflow tube on the reservoir.

I did hook up my OBD2 reader which has a live read function. ECT is the designation for Engine Coolant Temperature. I watched it climb to 195 and then I turned the AC on and both fans began to run and the temp began to fall albeit slowly. I have not refilled the cooling system with coolant, just distilled water. It seems like the water would boil 13 degrees before the fans would kick on? Could there be something else like as bad cap on the reservoir? If I had an air pocket? Or if it was overfilled? I have not drained or back flushed the system. Any guidance greatly appreciated.

Am I correct that the fans that come on when the AC is running that they run at half speed as compared to the speed they would run at if the temperature was reached and the left fan cycled on?

Thanks for your help

Chuck

[maxwedge]

You need the 50/50 mix, 225 is the turn on point in most modern vehicles. The 2 fans may run at a slower speed with ac as opposed to the high temp turn on, the programming for that can vary. Make sure the system is bled, info on how to is on youtube. The cap could be bad, not holding pressure, cheap enough, replace it.

[Buckeye Chuck]

Maxwedge
Thank you again for taking the time to reply. I think the cap may well be bad. I assume that the cap should hold pressure and not allow any coolant out of the overflow hose unless it exceeds the 15lb. Rating on the cap? But I also notice some deep brown sticky stains on the carpet of the passenger side. I may well have a leak at or in the heater core in addition to any other problems that I may have. I am going to get a hold of a Radiator Pressure Checker and test the system for leaks.

I assume it is a.pretty major project to get to, let alone replace a heater core on a 2004 Classic. I changed an evaporator on a 97 Grand Caravan once and the amount of disassembly to get to it was dauntng. If it is leaking from the core are there any simple easy problems I might uncover or is it most likely a leak in the metal requiring removal and replacement of the core itself. I realize I am getting ahead of myself going off on the heater core tangent...just my ADH acting up again!

Thanks again

[aleekat]

Most auto parts stores have a "loan a tool" program. Put deposit down for pressure tester kit, get your deposit back upon return. Normally the heater core leaks. No easy fix. You can bypass the core by connecting the 2 hoses at the fire wall. I used 1/2" piece of copper and 2 hose clamps. You just won't have any heat.