oil temp guage
 

I just bought a 2001 SPF and the oil temp guage isn't working. What do you think the most likely cause would be? Thanks, John

Low oil temperature?

My guage doesn't move until I've driven quite a distance, it takes a while for the oil temp to come up.

Mechanical or electrical type gage?

The sending unit is typically mounted on the passenger side of the remote oil filter housing. It's a sensitive probe that can be easily broken if not handled properly. I would start there and inspect that first.

-Dean #747

The gauge doesn't move after an hour of driving. I'll check the connection at the filter housing. Thanks alot guys.
John

If its a mechanical gauge, you would have to replace the whole thing (sender, capillary and gauge).

If its an electrical gauge, it could be a bad sender, bad wire or bad gauge. Check to make sure there is power being supplied to gauge.

Disconnect the wire from the sender, and measure the resistance from the sender to ground when engine is cold. Repeat measurement after driving car for an hour. If the resistance measurement is the same, replace the sender.

If the resistance measurement has changed, check wire for insulation breaks (improper grounding somewhere). Easy to just replace wire. Still have problem, test gauge by varying the resistance to the gauge using a decade box.

Oh yeah, like we have 2 or 3 of these lying around... :LOL:

Seriously, a great debugging procedure! But if you don't have access to a decade box, are you then pretty much pulling the gauge and sending it to Nisonger?

Thanks,

-Dean

WOW. Thanks for all the troubleshooting tips. I'll check it out by first finding out if it's elec. or mech. Anthem Motors, the Superformance dealer here in town (95.00/hr), could be an option but not a good one at this point. We'll see what's what first. Thanks again.
John

Touch the sending unit wire to ground temporarily (with the key in the ON position) and the guage should begin to move and ultimately go to top of range. If that works then the sender is bad.

John said: I just bought a 2001 SPF and the oil temp guage isn't working. What do you think the most likely cause would be?

John - Assuming it's the standard SPF gauge, it will be a Smiths mechanical gauge. Easy to tell: Does the face say "Smiths"? Is there a small tube enclosed in a somewhat larger wire spiral (which protects the small tube) running from the back of the instrument panel gauge to some point on the engine, or maybe to the remote oil filter block, at the front of the engine? If the answers are yes, you have a 1960's technology Smiths mechanical gauge. Assuming you do, the most likely cause for failure is a hole in the small tube that is enclosed by the wire spiral. That tube contains ether, which expands as temp increases, and causes a deflection of the needle (yes, it's really a pressure gauge calibrated to temperature). A small ding in the tube can allow the ether to leak out, and kill the gauge. There are no replaceable components on this gauge; you have to replace the entire thing. Mine has been replaced twice. If you replace yours, handle the new gauge carefully. Oh, and you might want to check the calibration of the new gauge before installing it. Put the bulb into a pot of water (suspended so that it doesn't touch the metal of the pot) and heat to boiling. Gauge should show close to 100 C when the water boils. If you have an accurate thermometer, you could also put it into the water (suspended as the bulb on the gauge) and check the gauge reading against the thermometer as the water heats and cools down.
Maybe better yet, replace the failed gauge with a new electric one. Autometer has some nice vintage looking electric gauges.
Good luck.

I think they are usually slow, but after 15 mins of "warmup", it should be reading a temperature

And after two hours?

"Houston, we may have a problem" :D

Just kidding, that is a long time for you to get a reading on the temp.

double ugly its a mechanical gauge and you can't repair it........just ordr another........I have replaced all my small smiths gauges with a cheaper one that actually has lights that I can see. I do however have a brand new , installed and removed to match the new gauges, Smiths oil temp gauge I'm willing to part with. Send me a PM if you are intrested...........

PM sent.
John

Just adding onto this thread. I had the same issue with a mechanical Smith oil temp gauge. Mine plugs into the oil pan. It takes about 10 minutes to register oil temp but it tends vary to extremes based on speed wind sppeeds likely cooling the wire. I didn’t know about the “ether” and tube compenentry. Mine might be a pure wire conducting heat and transferring the heat to a coil. I am curious if others have an unstable oil temp guage and I’d love to know if installing a heat shield wrap / tube along the wire would correct this.

No, it won't help. That long tube is really transmitting a pressure value to the gauge, not a temperature value. The gauge then converts the pressure reading to a temperature. My Smiths oil and water gauges are rock solid, predictable and consistent. Try just pulling your bulb out of your oil pan and sticking it into a cup of boiling water. If it doesn't go quickly to 100 degrees Celsius then the gauge is broken.

I have a Smiths electronic oil temp gauge, which is identical in looks to the analog gauge. A single wire to the sender in the oil pan, with power and ground to the gauge under the dash. It is rock solid. It takes 4-5 miles of driving for the oil to come up to temperature.

But with a wired sender you don't get to tell people that your temperature gauges use tubes that were developed by Eugène Bourdon in 1849 and that they require no power whatsoever to function. That's half the fun of mechanical gauges.:cool:

It's a Cobra, after all. It needs a "mechanical" gauge ;)

Cheers!
Glen