Hey all,

New to the forum, hoping to find an answer here.

04 Civic EX, ~157K, runs great. 2 weeks ago, on the way to work (30 mi each way, 99% hwy), noticed the temp gauge shoot up when pulling into the parking lot/driveway at the end of the drive. The radiator fan is not coming on, it does work w/ the A/C and brings the temp down.

Have gone through a pretty good troubleshooting routine, here's what I know

1. Coolant/radiator/thermostat are OK.
2. The radiator fan relay is good- have swapped it out, have bench tested it.
3. The fan works. Runs w/ A/C, have also bypassed thermo switch and it runs.

Based on that, I replaced the thermo switch. Same problem. BUT....

When I went through the troubleshooting, it states the #3 socket under the radiator fan relay should show 12V with key in pos II. It showed 0v. Checked fuse #14 under the dash, it was good. Removed fuse #14 under dash, tried to bypass the thermo switch, fan won't work. Put fuse back in, fan works w/ bypass, so fuse is good.

So it appears there is some problem with wiring/power to/from the relay?

I read another thread somewhere on the web about an older civic, similar problem, the guy had a loose wire (yellow) from the ignition switch, that fixed his issue.

Would appreciate any thoughts/tips about this.

 

If it always runs with the switch bypassed, the car wiring seems OK. Some third party switches have turned up to be duds. You can test the switch in hot water off the car.

 

Tested both switches, they are both good.

Here's something interesting that I discovered today. I have been thinking about possible electrical system causes for my problem. I was trying to recall if I had done anything to my vehicle recently that could account for this. All I have done in the last 30 days or so, was plug in my DriveWise device from Allstate, the device that measures/tracks your driving habits, with the possibility of a discount.

Anyway, I got home and turned off the vehicle, verifying beforehand that the radiator fan was not running. Engine temp had started to move up as the engine was idling in the garage with the A/C off. Then, I removed the device, and turned the key to the on position. I heard the fan running from inside the car. I looked under the hood to verify, and sure enough, the fan was running. I went inside for about 5-10 mins, went back out, turned the key to on, and again, the fan started up.

I think this may be the issue. Thought I would share w/ everyone, in case you are having a similar situation.

 

Update..

I drove the car the following day after removing the device, and temp stayed normal. Unfortunately, the day after that- back to overheating after driving.

Still not getting 12v to the #3 socket under the fan relay. Could this possibly an ECU issue?

Anybody with thoughts?