Gauge temp sending unit issues

[Team_Maha]

Hey yall, so for some months now I have been driving my 94 4.0 xj without a working temp gauge. The needle doesn't pass 100. I have tested the dial by shorting the plug's pin to ground and the needle pegs to the right. I have also put about 6 different sending units in it, changed the plug and even replaced the cluster.

Most recently I put tu238 and tu236 (duralast) sended units in and they appear to work for a few moments then fail. I have also put the Mopar unit in without any success.

Before I installed the last two unit I measured around 1.5k ohms from pin to body and now they are both open. I'm getting about 12.3 vdc from the gauge.

Am I the only one out here loosing these sensors left right? What should I look at?

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[8Mud]

Ohm test the black-light blue wire at the sender to battery ground. May be an open circuit or high resistance between the sender ground and the PCM, splice or connector. Ideally, it should be zero resistance, doubtful that will happen. Another quick check is to low voltage test the ground wire, if there is sufficient resistance there will be some voltage in the ground wire.
I'm not sure where the PCM grounds on the 94 is likely very near the PCM. That ground point may be corroded. Measure resistance between the body and battery negative. The ground strap from the engine firewall and the block is a known trouble spot.