Oil Temperature Gauge Failure

I just had a Van's brand oil temp guage go south. (No offense to you southern boys, I have no idea what that saying means.) It started the other day on start up it was pegged at 50F then jumped to 100F and was fine the rest of the day. Today, nothing but 50F, and it's been 100F all day! lol

How do I test the guage and sender to see which one is bad?

Also, there are 3 studs on the back for wiring. They are labeled;

S = Sender
G = Ground
I = ?

The builder has the I wired to the ground also, but his wiring is has been interesting to say the least.

Any help mucho apprciated.

I = power for internal light??

Gauge action definitely sounds like an electrical fault in the path somewhere. I would redo the ground first, that's dead simple and easy - if the sender (or sender wire) is at fault, the problem will still be there.

I took a .053 of a volt (I think that is how you say that.) reading from the sender and it seems to be fine. Pretty sure it's the guage. I ordered a new one from Vans.

airguy said:

I = power for internal light??

Gauge action definitely sounds like an electrical fault in the path somewhere. I would redo the ground first, that's dead simple and easy - if the sender (or sender wire) is at fault, the problem will still be there.

Click to expand...

No, there are 2 tiny red & black wires for the lighting.

I think "I" means ignition as in "switched" power. What is strange is the "I" was hooked to a ground and it worked fine.

The I terminal is for 12v.

Steve

Oil temperature gauge connections:

I = 12 Volts
G = Ground
S = Sender

Most gauges that work with resistive sensors such as oil temp, fuel level, fuel pressure etc. work via the same principle. They provide a constant current to the resistive sensor. They then measure and display the voltage across the sender to ground. According to Ohms law E=IR, if you provide a constant current to a resistive load, the voltage across the load will vary with the resistance. The gauge may also work in reverse, that is the gauge may display a higher reading as the voltage decreases, just depends on the design of the sender and the gauge.

You can test the Oil Temperature gauge by replacing the Sender with a 1k ohm potentiometer. The sender will typically measure about 650 ohms at room temperature and as the temperature increases, the resistance will go DOWN. So, if you connect a 1k ohm pot to the gauge you should be able to simulate the operation of the sender more or less. You should avoid adjusting the resistance of the pot to 0 ohms which might stress the gauge, shouldn?t but it might. Hope this helps.

The PO had the "I" & "G" connected to a ground and the "S" to the sender.....and it worked until I did some wiring and disturbed something.

I know it must sound silly of me to ask such a trivial questions about a oil temp guage hook up, but I studied this thing for hourts trying to figure out how it worked when it was hooked up wrong.

Sometimes things are best left alone, why this was working is one of them.

Thanks for all the input.