blue thing

[donm]

Under the dash on my '80 is a blue thing that looks like a fuse holder but inside is a fuse-like part that is wrapped with very fine wire. What is it?

[spider2081]

I think its a resistor in the overheat switch circuit of your temperature gauge.

[donm]

But I can see there's a break in the fine wire yet my temp gage seems to work ok.

[spider2081]

The are 2 senders in the top of the engine. One is the temperature sender. It is a variable resistor. The other is a temperature switch. The switch closes somewhere around 140 degrees and pegs the gauge needle. The resistor is in series with the switch to keep the gauge from burning out if the car overheats. With the resistor defective the only thing that happens is the temperature gauge is always going to read the temperature from the sender. I believe some cars used the over temp switch to light a warning light. The later cars have a red area on the gauge the needle is driven to once the engine reaches the switch temperature. When the needle is driven by the over temp switch the needle can be pointing to a higher temperature than the engine actually is.