Temp guage issues

[Nicketts]

Hi. Recently purchased an 82fi spider. Temp gauge inoperable. Was told mechanic replaced radiator a couple years back (and have all receipts to prove that) and he said the fan was working (it does) so he didn't bother with the gauge. After reading similar posts on this website, I've purchase both sensors for the gauge and will install soon. Likely the gauge will work then? Currently it does not budge at all. Other parts like wires, or fuses, that I should check? Everything else on that particular fuse is working. Are there new gauges available? Thanks!

[GeorgeT]

Gauge should have 12v going to it - check the voltage at the positive connector. The sensors are the grounds where the current flows: one sensor has variable resistance based on temperature and the other is a simple on/off ground based on temperature. Check the gauge by applying 12v to the + terminal and grounding the - terminal (s), gauge should peg, if it doesn't the gauge is bad.

[RRoller123]

Install the over temp sensor (not the variable resistor, but the "switch" type one that pegs the gauge) to the rear position in the head, closer to the firewall than the variable resistor one that actually moves the gauge and indicates temperature. That sensor goes towards the front.

[courtenay]

Install the over temp sensor (not the variable resistor, but the "switch" type one that pegs the gauge) to the rear position in the head, closer to the firewall than the variable resistor one that actually moves the gauge and indicates temperature. That sensor goes towards the front.

Interesting, in my '80 Fi, it's the opposite. The sensor that pegs the needle is closest to the radiator and the one that actually indicates the temperature is closest to the firewall.

[RRoller123]

I think that that is backwards per how it came from the factory, but there is a lot of myth surrounding this. The hottest part of the head is back by cylinder #4, so it could be argued either way; that the Pegger should monitor that area for early warning (my opinion), or that the gauge should do the same. I don't remember where I saw that the Pegger factory position was at the rear location, it was in a diagram or manual or something, but I guess it matters little, as long as the right wire is on the right sensor. The gradient isn't that big that it makes too much difference.

[spider2081]

The position of the senders in the head seems to come up often. I am not sure if Fiat had it the same for every car. It is important that the temperature sender that makes the needle indicate engine temperature be connected to the green/black wire and the switch that makes the gauge peg or slights and over temp light is connected to the gray/black wire. Maybe someone couple state how to identify which is the sender and which is the switch be appearance or test and not position.

[Nicketts]

I appreciate all the help. I will see what position they're currently in, and try to go by that as well as maybe wire color. Thanks everybody! I'll let you know.

[Nanonevol]

My temp gauge never moves but if I ground either wire from the head sensors, the needle moves. Assuming the sensors are bad so I purchased new ones. I think one needs to drain the coolant to remove these, correct?

[GeorgeT]

My temp gauge never moves but if I ground either wire from the head sensors, the needle moves. Assuming the sensors are bad so I purchased new ones. I think one needs to drain the coolant to remove these, correct?

You do not need to drain the coolant to change the sensors.

[RRoller123]

You might get some leakage from the "T" area at the front, which I think is up higher than the sensors at the head top, but not too much will come out and you can probably use a bunch of rags to sop it up.

[Nanonevol]

Thanks folks!

[Nanonevol]

Yeah! New sensors fixed my temp gauge! Now I just need my clock and gas gauge to work and I'll be at 100%. Good luck to the OP .

[RRoller123]

Palo Alto Speedometer is really good at the clock, and I assume all the other gauges too.

Pete

[Nicketts]

Hey, fixed the temp gauge. Per suggestions I got it to peg, but still didn't work. Took off air induction stuff so I could reach the sensors. Tried for hours but couldn't budge either one. Put it all back together and now gauge works. Now to try to lube the jumpy speedo...