Warning light wiring.

[Peterjojo]

Here’s kind of a stupid question. I’m concerned that my overheat warning light isn’t functioning and it’s getting hot. Does anyone know how to check this?

[Eagle]

The factory electrical manual shows only one test for the idiot light.

 

"Touch C307 terminal S to ground." [C307 is the terminal that plugs onto the temperature sender in the left rear corner of the engine.]

 

If the idiot light illuminates, replace the switch (the temp sender).

 

If the light doesn't illuminate but you know the bulb is okay, then you have a broken wire or an open connection between the sender and the bulb. (Could also be a damaged trace on the printed circuit board of the cluster itself.)

[Pete M]

a full cluster swap will give you a real gauge.  

[Peterjojo]

Yeah. I was talking to my Jeep guru yesterday about replacing the thermostat housing with one that has the extra hole to install an after market temp gauge. But man it’s so hard to tell if what I’m looking at is actually going to fit my 87. Getting parts it becoming very hard. The Cherokee from that 86-90 era are the same though right?

[Pete M]

an 87-90 full cluster will go right in.   swap out the temp and oil pressure switches for sending units and go.  should be a link to a writeup in the link in my signature.  also should be a link to modding the odometer on the new cluster if you want the mileage to match.