Temp gauge at max with batteries off!

[Baltimore Sailor]

Now here's a good one I haven't seen before: with my battery switch OFF, my temp gauge is pegged at the max. As soon as I turn the key to start the engine, it drops back down to the min mark, and then works normally.

As soon as I turn of the engine again, it maxes back up the top.

What could possibly cause this behavior? I should just probably get a new gauge, right?

[Tenorsax]

My temp gauge has the opposite problem. It goes to max when I turn the switch on. Below is a thread that another member sent me. I think it might help you:

"My temp gauge also jumped to a full scale reading. It was due to a broken wire inside the gauge (which I'm sure I snagged and broke). I think mine works like this.....

There are two coils that both get 12vdc across them. One goes directly to ground and the other grounds through the sending unit. They create opposing magnetic fields that pull on the bottom of the needle. The hotter the sender gets, the less resistance it has and the more current can flow though it's respective coil.

When the "sender unit's coil" broke and was open, the other coil pulled the needle to full scale.

I broke out the magnifying glass and little solder iron tip. I was able to resolder the broken coil wire and it's working fine now.

I'm glad to keep the original gauge as it's part of a cluster... change one, change them all...."

good luck,

Mark (I live in the Columbia River Gorge and have a Santana 27, thus the user name).

[Baltimore Sailor]

Well, I don't have the problem of the gauge being part of a cluster, so I could swap mine out easily. What I can't figure out is how the gauge can be off the zero mark at all with no power in the system.

That's just weird.