The Stovebolt Site Forums The Shop Area Engine Shop Another temp gauge question.

I bought a 66 with an aftermarket temp gauge, Its a new gauge mounted in a cluster under the dash and the engine is a 350.
The gauge is not registering so I looked under to see if it was connected and I noticed that the wire was bent over pretty far where it connects to the gauge.
Will a bad bend in the sending unit wire ruin the wire, I bent it back and its still dead.

How do I check the gauge and sending unit with a meter?

Billybolt,

The wire would only be ruined if it is broken!! The gauge should have two wires going to it I think, one power wire, and the wire to the sending unit. If you have voltage to the power wire when you turn on the switch, half your battle is won.

The other wire on the back of the gauge, (the bent one) as you state, goes to the sending unit. The sender is a variable ground. If you put a wire from that terminal (on the gauge) to ground with the key on, the switch should do something...peg at hot, or peg at cold. This proves the gauge is good, and the wire to sender is defunct, or sender is NFG. This IS a electric gauge isn't it? That wire isn't a capillary tube is it?

Stuart

The wire to the sending unit was thick and almost felt like it was a tube, it wasn’t an actual 16 gage wire it was about an 1/8 " thick and was stiff not flexible like a wire.
I should say it was Pose able.

Oh also it does have a power wire daisey chained with the other guages

Just make sure the two wires do not/did not short across to each other. I made that mistake, having the wires short across the back of the gage. It ruined the gage instantly. Also, make sure the sending unit is grounded to the block. If you wrap it up with teflon tape (or equivalent) and it doesn't make ground, I don't think it will work. I used tape, but only sparingly and at the deep portion of the threads.

It's got to be an electric gage. No way it is a capillary tube temp sending unit.1

Billybolt,

The daisey chained wires could be for lighting. I would guess your gauge is mechanical, and might be toast!

Stuart

What's the difference between a mechanical and electrical gauge?

Billybolt,

The electric gauge uses a sending unit that is in the block and is wired to the gauge..the mechanical gauge has a capillary tube which is filled and sealed and goes to a probe that is in the block.

The tube on the mechanical unit isn't serviceable...if it is broken or NFG, it's time for a new gauge. The difference is obvious between these two types. The capillary tube is, as you described, a little tube, not a wire.

The old AD rigs used a small copper tube, you indicated yours was a black plastic looking tube...again, obviously not a "wire".

If yours is mechanical, where the tube goes into the back of the gauge, there will be NO connection...it will end in a weird looking crimp, and won't be detachable.

Both styles are accurate. Some old timers feel the mechanical type is more accurate. I think they are more expensive, and not as popular today.

Hope this helps!

Stuart

Thanks automarc!
One last thing, When I reinstall the new unit do I need to bleed out any air in the block, or any other technical suggestions.
I went home to take a look at it and it has a cylinder that sticks out of the gauge and it is soldered to the lead.

Thanks,
Billy

Billybolt,

Just stuff the new one in and take a drive!


Good Luck, Stuart