Hi, So a while back I snapped my temp sender off in the head of my 93 and I used an adapter that you put inline with your upper radiator hose. My question is what is the wire gauge for the connector that goes to the sender? I need to extend it to said adapter and cannot seem to find it anywhere online.

 

per factory manual for 1990 XJ that wire at the coolant sensor is 18 gauge. Diagram MJ-XJ 28 is the source for this info. Interestingly that wire reduces to 20 gauge as it goes thru various connectors on route to the dash

 

It carries negligible current, so 20-gauge is plenty. Only one wire to the sensor? How's it getting grounded since it's not screwed into the head?

 

Yes that setup os useless without the sensor grounded to the block or frame. A hose clamp around the brass hex with a wire squished under it and grounded to the block or frame will make the sensor work.

 

I had a wire going from the base of the sensor to a bolt on the A/C Compressor and that's how I knew it was reading as overheating.