Sending unit or gauge malfunction?

[pryord]

The oil pressure gauge on my '67 isn't working. How does an electrical newbie determine if the problem is with the gauge or sending unit?

[Quicksilver]

Is the gauge all the way up or down?

If everything is working and you disconnect the wire at the sender it should peg the gauge all the way to the top.

If the sender has no resistance or the gauge is dead the needle will be all the way at the bottom.

[pryord]

Hmm, I disconnected the sending unit and the gauge stayed all the way down. I tried the same thing on my SC and got the same results. I know the pressure gauge on my SC works, so, I'm not sure it's true that the gauge will go all the way to the top when the wire is disconnected.

[ossiblue]

Originally Posted by Quicksilver

Is the gauge all the way up or down?

If everything is working and you disconnect the wire at the sender it should peg the gauge all the way to the top.

If the sender has no resistance or the gauge is dead the needle will be all the way at the bottom.

This is the way it works on my car also--can't explain why your SC is different.

On your 67, if you disconnected from the sender and the needle is still down, the sender wire itself may be shorting to ground somewhere along it's run, or the gauge is bad. I know it's a PITA to remove the gauge on the early cars, but you may try removing the sender wire from the back of the gauge and see if the needle pins to the top. Also, run a continuity check on the sender wire and a voltage check on the hot wire to the gauge while you're "in there."

[pryord]

Well, here's one problem, I'm an idiot!

It's the oil temperature gauge that isn't working, not pressure.

I've been disconnecting the oil temp gauge. That's the one to the right of the fan housing, right? How do I tell if the OIL TEMP gauge or sending unit is the problem?

Thanks,
David

[3.2 CAB]

I believe that you can test the temp gauge/sensor the same as the other oil level/pressure sending/sensor units.

[Porsche_monkey]

Originally Posted by pryord

Well, here's one problem, I'm an idiot!

The root cause to issues is rarely found this quickly. We can all learn something from this post.

This sort of honest self appraisal would be beneficial in the Off-Topic Forum.

[Porsche_monkey]

On a more serious note: You should be able to remove the sensor wire and have the gage respond in one direction, then short that wire to ground and have the gage move to the opposite end of the scale.

Typically the gages work properly or not at all, so if they move when you turn the key on the are likely okay. If you can not get them to move by opening then shorting the lead at the sensor then you have a sensor or a wiring issue.

Now if I could just remember where that temperature sensor is located....