Temp gauge and fans

[bytes311]

I experienced a weird issue with my temperature gauge and fans this weekend. Yesterday, in stop and go traffic, my temperature gauge rose just below the 220 tick before the fans kicked in and knocked it back down. Today, I let the car idle in my driveway until it got warm enough to run the fans, and the fans kicked in just a little above the second tick and maintained that temperature the entire time.

I know our gauges aren't the most accurate, but I'm confused why my fans came on later while driving vs earlier while idling in my driveway. Is this considered normal operation?

My car has the water pump auto-bleeder installed. I checked the radiator for air pockets and there were none. The coolant in my header bottle also maintains the right level of coolant.

Thanks!

[Michael]

My first guess is either a temp switch is wonky or one of the fans maybe inoperative or weak?

[bytes311]

My first guess is either a temp switch is wonky or one of the fans maybe inoperative or weak?

Hmm... my fans are the new, low draw DMCH fans. They both run perfectly fine as far as I know.

[David T]

Just because you have an auto bleeder doesn't mean you can't have some air trapped in the system. I would get a pressure tester, pressurize the system and bleed it manually at the water pump and the radiator. Do you have the old style pipe with the "O" switch on the top? Or is the "O" switch sticking out the bottom of the pipe? If this happens again after manually bleeding the system, replace the "O" switch. Also make sure you have the uprated circuit breaker for the cooling fans and there is no heat damaged wiring or connections in the cooling fan circuit. if you have the fan fail relay either replace it with jumpers or some better relay than the OEM one. Check the coolant level cold. The header tank should be 1/2 full when cold.

[bytes311]

Just because you have an auto bleeder doesn't mean you can't have some air trapped in the system. I would get a pressure tester, pressurize the system and bleed it manually at the water pump and the radiator. Do you have the old style pipe with the "O" switch on the top? Or is the "O" switch sticking out the bottom of the pipe? If this happens again after manually bleeding the system, replace the "O" switch. Also make sure you have the uprated circuit breaker for the cooling fans and there is no heat damaged wiring or connections in the cooling fan circuit. if you have the fan fail relay either replace it with jumpers or some better relay than the OEM one. Check the coolant level cold. The header tank should be 1/2 full when cold.

Thanks David. My otterstat is facing downward inside the pipe, and I have the uprated CB's for my (low current) fans. Both fans are jumpered in the relay compartment. The issue doesn't appear to be with the fans themselves, but with the timing of the otterstat in relation to the temperature gauge. If I let my car idle up to temp for the fans to cycle, they generally come on just above the first tick. But when I went for a drive and sat in traffic for a few minutes, the fans didn't cycle until the needle was just below 220.

That drive was yesterday. Today, I let the car idle in my driveway and the fans cycled just above the first tick as normal.

I'll manually bleed the water pump and radiator as suggested.

[Bitsyncmaster]

Next time that happens try turning the AC on to see if the fans turn on. If they do that would tell you the problem is the otterstat or wiring of the otterstat. The otterstat wiring goes through the bulkhead connector and a diode in the harness in the relay compartment. I would suspect the otterstat circuit rather than the temp gauge circuit fault.

[bytes311]

Next time that happens try turning the AC on to see if the fans turn on. If they do that would tell you the problem is the otterstat or wiring of the otterstat. The otterstat wiring goes through the bulkhead connector and a diode in the harness in the relay compartment. I would suspect the otterstat circuit rather than the temp gauge circuit fault.

Immediately after I got home after my temperature scare, I let the car idle in my drive way for a couple minutes and confirmed the fans turn on with the AC. Thanks Dave, that wiring gives me another area to investigate.