Testing an oil temp gauge or sensor

Black Mamba · #1 (**permalink**) 04-29-2010, 11:13 AM

Is there an easy way to test either an oil temp sensor or gauge? Not sure which is the culprit but the needle never moves. This is a Smith gauge if that makes a difference and the motor is a 351 HO.

MaSnaka · #2 (**permalink**) 04-29-2010, 11:46 AM

In my experience I had to test an oil pressure gauge and the tech at Stewart Warner said disconnect and ground the sendor wire and if the gauge went to the max reading the gauge was fine. I don't see why it would be any different for all electronic gauges. Good luck,

John

Black Mamba · #3 (**permalink**) 04-29-2010, 12:04 PM

Thanks. Read something similar to that test in one other place, the only place I could find info, and so I guess this adds validation. I'll give it a go this weekend and see if I can't sort out the problem. Thanks again.

Calbullet · #4 (**permalink**) 04-29-2010, 12:34 PM

BM, most Smiths gauges are mechanical and not electrical, this means there is not a electric sender to ground. the Smiths gauges have a solid connection between the gauge and the sender at the end of the line. to check the gauge you will have to put the sender in a pan or cup of hot water to check

Black Mamba · #5 (**permalink**) 04-29-2010, 02:09 PM

Quote:

Originally Posted by Calbullet

BM, most Smiths gauges are mechanical and not electrical, this means there is not a electric sender to ground. the Smiths gauges have a solid connection between the gauge and the sender at the end of the line. to check the gauge you will have to put the sender in a pan or cup of hot water to check

OK, looks like I'm stuck again then. If I put the sender in hot water it's effectively like leaving it mounted where it is as I'm sure the oil is warming nicely while I drive. How do I tell which is defective otherwise?

Calbullet · #6 (**permalink**) 04-29-2010, 02:18 PM

BM, 9 times out of 10, it just went dead. there is no fix, other than purchase a new gauge. the gauge and sender and connecting tube are one. you can send it to Nisonger Instruments and get it repaired, but the cost of a new one is about the same. most likely engine vibration just weakend the tube and there is a leak.

Black Mamba · #7 (**permalink**) 04-29-2010, 02:51 PM

Quote:

Originally Posted by Calbullet

BM, 9 times out of 10, it just went dead. there is no fix, other than purchase a new gauge. the gauge and sender and connecting tube are one. you can send it to Nisonger Instruments and get it repaired, but the cost of a new one is about the same. most likely engine vibration just weakend the tube and there is a leak.

Thanks Cal. I'll try to get a look at it sooner then later. I may take it over to North Hollywood Speedo and let them look at it, worse case scenario is possibly having them switch the gut to something more reliable... and electric. The other option is I think these are the same as on Mini's - 52mm - and I can have one sent over for about $150.

sllib · #8 (**permalink**) 04-30-2010, 06:10 AM

John;
On initial fire-up both my temp gauges were bad and had to be replaced at no charge by Autometer. I was very careful not to kink the leads when I routed them around the engine and through the dash and, as soon as I realized something wasn't working I shut it down. I used a pan of boiling water to verify the fault.
Bill Stradtner

Black Mamba · #9 (**permalink**) 05-03-2010, 08:52 AM

Got it out over the weekend and tried the cup of hot water trick but that didn't move the dial any. Pulled it apart and it looks simple enough, just a bimetallic spring moving a gear slightly and the gear moved fine. I gave North Hollywood Speedo a call, their about 4 miles from my house and they've done excellent work on gauges for me in the past, however the estimate was $160 which exceeds the price of a new one.
The Mini's gauge is the same but the length of the capillary is about 1.5' shorter so it wouldn't work. Reckon it's time to call Nisonger.