Cosmo Kramer

OK so I pretty much have my car dialed in after the fire, but have an issue. The sensor on the driver side of the water bridge (one for gauge) had a bad connection. When working on the car, I pulled the large terminal off the sensor to check to see if it was making contact while the car was idling. When I pulled it off the ISV bumped the idle up to 2000 rpm for abut 10 seconds? Is the temp gauge circuit tied to the LH in any way or do I have a short somewhere? Car runs perfect other then I have this flakey temp gauge and the occasional random idle bump.

I found this to be very odd...

John Speake

Temp gauge sensor isn't linked to the LH in any way.

Cosmo Kramer

Ok thanks John, my wiring must have been shorting to ground causing something wonky. I have redone the temp harness hopefully that solves things!

Cosmo Kramer

So I have verified the wiring at the sensor is ok but my temperature gauge is still intermittently working. I am thinking the place to start is to clean the grounds. What is the best place to start, engine ground strap and the ground at the back of the engine? Also I have powder coated my water bridge does the Temp2 need to be bolted to a clean surface or is it grounded through the wiring?

John Speake

It is essential that temp 2 and the gauge sensors both make a good ground connection through the body of the sensor. With a DVM on ohms, measure from each sensor body to engine block and check you have a reading very close to zero ohms. If you short both the DVM leads you can check what a dead short registers on your meter (sometime 0.3 ohms due to lead resistance)

It is quite possible that the powder coating is causing your problems if none existed previous to that work.

Cosmo Kramer

Thanks John I will do that. Do the orange water bridge gaskets compress enough to get metal contact to the block? Just wondering if I need to clean the powder coat under the bolt heads of the water bridge as well.

SMTCapeCod

If you do, please post some tip on doing so without de-laminating the whole coat, of coat? Or maybe that's an unfounded concern, but I've had some chipping and it seems to creep.

Imo000

Put a temporary wire from the body of the sensor to the chassis and see if that works.

Cosmo Kramer

So took my meter and I was getting 5 ohms from the sensor body on the temp2 and gauge sensors to both the block and the chassis. The sensors weren't the culprit I found they were grounding fine through the threads. I removed one of the water bridge bolts and carefully dremelled the powder coat off the size of the washer on the bolt. Bingo, now 0 resistance from sensor body to the chassis. I will see how that works.

Cosmo Kramer

So two good runs in the car and this was the problem. If I had to do the powder coat again I would put a bolt and washer in one of the water bridge mounting holes to keep the coating off the mating surface and ensure the sensors get a good ground.

davek9

Wow.. great find and tip, some good troubleshooting there, thanks for the follow-up!!!

Dave