temp gauge not working Help?

Okay, long story short I recently had the head off the motor to fix a broken exhaust stud. After reassambly the temp gauge quit working. I assumed that I must have damaged the sending unit ontop of the head either during repairs or when I rolled the jeep the week before. So I replaced it, and just to be on the safe side I replaced the unit on the thermostat housing as well. That did not fix the problem and after a couple weeks trouble shooting the wiring I just gave up and bought a aftermarket gauge. I put the new sending unit in that came with the gauge, ran the wire to the gauge and connected the 12v power and ground to the back of the gauge and of course this gauge doesn't work either. The old gauge never moved off the bottom of the scale except to peg while starting. The new gauge just stays pegged as soon as the power is turned on. I am no longer sure of anything after this.

So I want to ask a couple stupid questions.


The ground strap on the firewall should be hooked to the rear driverside head bolt correct?

Has anyone seen this before?

I would appreciate any response even if its just to point and laugh because I just don't know what to do with it any more.

On a '96 cherokee:

--AT THE BACK OF ENGINE AT FIREWALL--

-disconnect the harness from the sensor, key on, -gauge reads min.. With paperclip or pin connect the connector to a ground- gauge reads max. that checks the wiring. (turn key off!!)

There are two types sensors-one is for on/off warning light and has a black connector plastic. (temperature switch on or off only)

The one for Gauge has white connector plastic. (When temperature changes it changes the resistance) (less R as temp goes up = more current thru meter = higher temp reading)

Both types must have good ground at threads into engine.(thread sealer not needed and just snug, not over tightened.)

Hope that helps,
O

The ground strap can be connected to the head wherever it can make a good solid connection. Make sure paint, gasket materials, etc. don't interfere. Check the body end of the strap as well. Scrape or grind paint off to a clean metal surface and apply grease to prevent oxidation.

Found my problem, thanks to orange and heavyequipment for the response, the sending wire was grounding to the sending unit due to a missing washer. OE temp gauge is kaploey but the aftermarket one now works.

Excellent!

Happy Trails,
O