Oil Temp Gauge problems

Jerry Chabino · #1 (**permalink**) 02-03-2002, 01:30 AM

The oil temp gauge on my Unique has never worked. It is an SW. How can I diagnose the problem. It does not move offf the peg at all.

Tnx,

Jerry:

Cobra20646 · #2 (**permalink**) 02-03-2002, 05:41 AM

Jerry,

I'm assuming electric gauges here....

If you have a simple volt meter, make a few simple checks.

1. First step is to measure the voltage at the oil temp sensor. Should indicate "something", but not ZERO volts. (ignition switch ON)

2. If you have a voltage reading, have an assistant watch the gauge closely while you short the sensor wire to ground. Short it and un-short it as quick as possible, you will damage the gauge if left shorted too long. If the gauge needle moved, replace the sensor.

3. If you had zero volts in step one, your going to have to get to the back of the dash to check the connections on the gauge.

4. On the back of the gauge, there are two terminals. One is usually labled '1' or '+' and should measure 12 volts with the ignition switch on. The other terminal is usually labled 'S' and connects to the sensor. Measure the voltage at the 'S' terminal, it should show something.

5. Tests results...

If you didn't measure voltage at the 1 or + terminal, you need to repair the wire from the gauge to the ignition switch.

If you didn't measure voltage at the S terminal, but did at the 1 or + terminal, the gauge is bad.

If you measured voltage at both the 1 or + terminal and the S terminal, but didn't at the sensor (step one) then repair the wire between the gauge and the sensor.

Happy trouble shooting

- Jim -

Bob Putnam · #3 (**permalink**) 02-03-2002, 06:10 AM

Jim,

I couldn't have said it better.

I'm going to let you answer all the electrical problems from now on!

Jerry,

If it's a mechanical gage and the bulb is in the pan, the gage is toast.

Double Venom · #4 (**permalink**) 02-03-2002, 07:42 AM

Jim,

You wouldn't want to wire the next DV would you?

DV..he who gets lost when replacing a fuse doesn't fix the problem!

Jerry Chabino · #5 (**permalink**) 02-03-2002, 08:32 AM

Thanks much Jim !!!! I did exactly what you instructed and the sensor is bad !!! Really appreciate the help.

Regards,

Jerry

Cobra20646 · #6 (**permalink**) 02-03-2002, 10:35 AM

Jerry,

Glad I could help you find the problem.. After posting my responce above, I got to thinking about where the sensor is mounted..... if other than in the pan. My thinking was that maybe the sensor is not grounded!!!! If you haven't already pulled the sensor, you might take a short length of wire and hook one end to the engine block and the other to the body (threaded part) of the sensor, and see what happens.

Bob and DV

Every now and then someone asks a question that I know something about

.... and Ed, I'm looking for something to do after I finally get around to retiring.. someday...

- Jim -

Jack21 · #7 (**permalink**) 02-03-2002, 04:13 PM

Jim,

If you know anything about automatic fuel tank gauging systems, like the ones they use at gas stations, I have another potential job for you a little bit closer to home. Although, like you, the thought had occurred to me about building cobras as a retirement income.

Cobra20646 · #8 (**permalink**) 02-03-2002, 06:58 PM

Jack,

What's that old saying....... "So, how does that work?" answer: "works fine!"

The State of Maryland has a contract with an outfit called Automated Fuel Systems or something likt that, and I've watched their techs pull their hair out over some of the problems with those systems. I know absolutely nothing of how those systems do what they do, but I've been in electronics for .... lets see now... over forty years now, so I guess I could still learn how they do what they do

I'm always interested to hear about ways to supplement my retirement income. Heck,... we're right across the river from one another. We'll have to get together one day and talk!

Say, how come you arn't a member of the Capital Area Cobra Club?

- Jim -

Bruce Botti · #9 (**permalink**) 02-03-2002, 07:45 PM

Bob,
Just curious, but why can't you mount a mechanical gauge bulb in the pan? Thanks in advance!
Bruce

Jerry Chabino · #10 (**permalink**) 02-03-2002, 08:06 PM

Jim and all,

My sensor is mounted in the oil cooler. I thought they all were mounted there. SHEESH what do I know. Thanks again .

Jerry

Double Venom · #11 (**permalink**) 02-03-2002, 08:20 PM

Jerry,

It's in the cooler!????

Run a ground to it man! You will probably have to move it eventually, but I'll bet it works if you ground the sensor.

I got that one !

DV

Bob Putnam · #12 (**permalink**) 02-04-2002, 05:59 AM

Jerry,

There's nothing wrong with mounting the bulb in the pan - in fact, it's probably the best place. I was asking(in my

way) whether you actually had the bulb immersed in the oil.

Jerry Chabino · #13 (**permalink**) 02-04-2002, 06:01 AM

Ed,

Yep it threads into the cooler. The cooler itself is mounted on a frame cross member. The sensor itself has only one wire which is power. I thought that the cooler being mounted on the frame would be enough ground. Any ideas ??

Jerry

Double Venom · #14 (**permalink**) 02-04-2002, 06:29 AM

Jerry,
I know a lot of the coolers mount through rubber >> Bob has a good point...sensor isn't in an air pocket is it?

Darn..thought I had that one!
DV

Jerry Chabino · #15 (**permalink**) 02-04-2002, 07:19 AM

Ed,

I checked for ground between the sensor base and the block. Ground is good. Regarding the possibility of an air pocket, when I took out the sensor oil flowed out.

Jerry

Cobra20646 · #16 (**permalink**) 02-04-2002, 03:46 PM

Guys,
This is where I pass off the baton

... but have to ask a question just the same....
With the gauge needing to see something above 140 degrees before it starts it upward movement, is it possible that the oil cooler is doing a fantastic job at cooling the oil that it never gets that hot around the sensor? If I'm wrong in my thinking, than I guess it's back to the problem of a defective sensor.
A resistance check of the sensor is also a way to tell if it's bad. My old notes show a resistance of 1000 ohms should be equal to a gauge reading of just a tad over 140 degrees, and a resistance of 470 ohms equal to a reading of 200 degrees. I don't have a cold (room temp) resistance to check, but I have a good sensor out in the garage that I'll try to dig out and measure..... will post that when (if?) I find it.

- Jim -

Double Venom · #17 (**permalink**) 02-04-2002, 04:35 PM

Darn!

Back to the above! Change sensor and let us know.

DV

Cobra20646 · #18 (**permalink**) 02-05-2002, 12:13 PM

Jerry,

The SW oil temp sender I have reads around 10,000 ohms at room temperature.

Hope you problem is solved now.

- Jim -

Jerry Chabino · #19 (**permalink**) 02-05-2002, 01:45 PM

Jim,

I ordered a new sensor from Enzo. I tested the old one by using an ohm meter . I touched the black lead to the base of the sensor and the red one to where the power wire is hooked on. There was no reading. My friend tells me that the circuit is open and that the sensor is bad. I just know enough about electricity to be dangerous !! I'll let U know how it turns out.

Many thanks,

Jerry

Jerry Chabino · #20 (**permalink**) 03-01-2002, 09:19 AM

Hey all,

I finally got a new temp sensor from Stewart Warner. Took 2 weeks !! I installed it and everything works fine. Once again U guys come through !!!

Thanks again.

Jerry