Asmar

My 1996 Acura Integra is having an extremely weird overheating issue. First of all, the radiator fan isn't turning on by itself. I unplugged the plug going to the coolant temp sensor and stuck a paperclip in it and the fan stays on while the car is on. Now my car doesn't overheat unless the climate control settings are set to cold (my car doesn't have A/C). The temp keeps climbing once it's under the cold setting on the climate control. Once I slide it back to hot the temp starts going back to normal.

What I've done so far:
- New thermostat (OEM Honda)
- New temp sensor (OEM Honda)
- New radiator cap (OEM Honda)
- Checked all fuses (all are good)

I was told if I changed the temp sensor with a new one, the fan would come on by itself again. The fan only turns on when i unplug it from the temp sensor and stick a paperclip in the plug. The paperclip only prevents my car from overheating as long as the climate control setting from inside my car is on hot. The fan speed for the climate control can be on "off" or maxed out to "4" and the car won't overheat, it just needs needs to be on hot. As soon as you slide it to cold the car's temp will start climbing up and it will keep going. I can't figure out what's going on! How do I fix this? Why won't the fan turn on by itself even though I put a new temp sensor switch? I should also mention that I checked the fan relay under the fuse box that's in the engine bay and swapped it with another relay in that fuse box (I believe it was the heater relay) as they were both the same relays and that didn't do anything either. PLEASE HELP!!!

fcm

Sounds like at least two problems, a bad ECT switch, [needs to be replaced] and a rad problem, most likely a restriction, [clogged], when you turn the temp. to cold you take the heater core out of the "loop" and you lose engine coolant cooling.

You can try having the rad flushed out, but most likely you will need to replace the rad. 94

silvertaxasteg

You can test the switch by sticking the probe in water/coolant and bring it to a boil. At 196-203 F the terminals should have continuity. If not, it's a bad switch. It can happen.

If you're jumpering the harness for the switch successfully, that's really the only thing not making the fans come on.

Follow fcm's advice.

Asmar

I finally saw the fan turn on by itself. The car never overheats while the climate control setting is under hot. When the climate control setting is under hot, the fan turns on by itself and the car never overheats. When you move the climate control setting from hot to cold it starts overheating. The climate control doesn't have to be on, it can be under "off" or maxed out at "4" and it'll react the same. Do you think my radiator is bad? Anyway to test and see what's going on at this point?

Temp sensor is working now. Read what I wrote above in response to fcm and let me know if you know what's going on. Thanks in advance for your help.

silvertaxasteg

Good to know the sensor is working. I'm hesitant to blame a new part, but it happens. If you have to turn on the heater to keep it from overheating, that means the effective surface area of the radiator has been reduced quite a bit. You'll still have to either flush it or replace it. Or you might get lucky and find a plug of some type in the radiator hoses that is blocking sufficient flow. Flushing isn't so reliable anymore with the parallel flow radiators - the flush will just find the path of least resistence and leave the blockage alone. A harsh chemical flush might work, but you have to be real careful with how long you let it sit.

Either way, what fcm says is still valid.