Temp light

[Handmedown]

I have a 72 with full gauges . It also has a temp light under the fuel gauge, what triggers the light. Does it have a separate sending unit, or does the temp gauge trigger it when it gets up to a certain temp?

[AirSpeed]

I have full gauges as well, in both my trucks and I've never seen the temp light come on, even when I actually did overheat my truck. I think they're there because it's cheaper than removing it for a gauge filled panel.

[Handmedown]

I'm going to hook it up to a sending unit anyway I don't like having stuff that doesn't work. I already installed a temp gauge in the empty spot below the fuel gauge I am going to conect that to a sensor on the trans

[72longhornII]

I had a 65 impala with a 283 and I cooked the motor when the thermostat failed. The best thing was to install a temp gauge so you know what temp your running at. My dad put one in my 72 when he had it along with a tach and vacuum gauge.

[Handmedown]

I do have a gauge. I plan on running both, I just hate having on light in the dash that does nothing.

[VetteVet]

Originally Posted by Handmedown

I have a 72 with full gauges . It also has a temp light under the fuel gauge, what triggers the light. Does it have a separate sending unit, or does the temp gauge trigger it when it gets up to a certain temp?

The temp light is used on the light cluster not the gauge cluster. The sender and the wire for it are are in the same locations as the gauge sender and wire, but the sender is different for the gauge cluster and the wire is pinned in a different spot on the cluster plug.

The light cluster is pinned on spot 5 on the light cluster and it is moved to the no.6 spot on the gauge cluster. You probably don't even have a wire for it on spot 5 and you may not have a light bulb in the cluster.

Here is the illustrations for the two clusters.

The light cluster.



Notice the temp wire on spot 5.



Here is the gauge cluster.




The wire is moved to spot 6. There are other differences too as you can see.


Here is a diagram of the gauge cluster showing the circuit board and the light below the fuel gauge . The red dotted line is the path for the temp light that is no longer used.



I suppose if you add a light sender and the wire to the no. 5 spot in the cluster plug, the light would work.

In addition the wire from the light sender is routed to the key switch on trucks and then to the cluster plug so that the key switch will ground the light wire during engine start, to test the bulb to be sure it isn't blown out. I can't say if the gauge trucks have this feature in their ignition switches. I assume that it is, because it retains the brake warning light feature of the idiot light cluster, which is routed similarly.