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Ohming a temp sender

bigbovine

NAXJA Forum User
Location
Tennessee
OK, I got a 96 Cherokee with, I6 engine and standard transmission recently. Temp sender at firewall on block was broken , so went to parts store and got a new one and installed it.
Temp gauge when vehicle is warm shows around 230 to 245 degrees. I was told to ohm the sender to check it. I did, and while in that range of temperature I gave above, it read between 135 and 145 ohms at sender.
The electric fan cycles on and off with the rise and lower of the ohms, so I don't think I am running 240 degrees (It runs off a different sender).
I took a Temp Gun that I use in heat and air work (I do not trust it to give me actual temperatures, but have tested it and found it gives accurate differances no matter what it says the temperature is, does that make sense?) and the upper heater hose read between 170 and 185 while the block in the same area would read 190 to 210 (So I am for certain the pump is working).

I then pulled the gauge cluster to check the wires at that end to see if I am getting good ground there. That is where I got lost. I see the 3 screws in the back labeled "grd", "ign", "tsu" (I believe that is right). I read somewhere to take a wire and ground at the gauge but do not want to do something that messes the rest orf the cluster up.

Here is where I got my information
http://www.autometer.com/tech_faq_an...x?sid=1&qid=57
http://www.marshallinstruments.com/f...tail.cfm?id=33
http://www.marshallinstruments.com/products/9204.cfm

Am I right in saying that I am running at normal temps based on ohms at sending unit and something is wrong at the gauge?
Also, if I want to run a "better" ground to the gauge on the cluster to check it (Remember that it is a plastic sheet with copper running around and labeled screws holding gauges with one pigtail hooked in, sorry I understand you guys may know this but wanted to make sure), would I run that wire to the screw labeled GRN (It runs to several so I would assume it is ground)?
 
Courtesy of Cruiser54:

Improving the Instrument Panel Ground

The ground point for the complete instrument cluster on your XJ or MJ is located up under the driver’s side dash. If you lay on your back and look up under there with a flashlight, without wearing a hat, you will see a black wire attached to a shiny piece of metal almost directly above the hood release knob. The screw will have either a ¼” or 5/16” head on it.

This ground point is responsible for handling the ground circuit for the following items: Dome lamps, Seatbelt and key warning, trans comfort switch, wiper switch, headlamp switch and delay module, fog lamp switch, cargo lamp switch, all instrument panel grounds and illumination, power windows and door locks, cruise control dump valve, and a few more things.

The problem is that where the ground point is located does not have a good contact with the chassis where the ground should be. The solution is simple.

Make up a jumper wire with #10 gauge wire about 10” long. On one end, crimp on a ¼” round wire terminal. On the other end, crimp on a 3/8” round wire terminal.

Remove the screw from the existing ground wire and attach the small terminal of your jumper so that the original wire and your new jumper share the same attaching point, one over the other.

Look above the driver’s side plastic kick panel just forward of the top of the hood release knob. You will see an 8mm stud there. Attach the large terminal end there with a washer and nut over it tightened securely.

**Special note for Comanche owners: Make your jumper wire 12” long and attach it on the driver’s side kick panel close to the fusebox on the 8mm stud.**
 
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