Temperature sensor?

I recently got a 93 XJ & swapped another 93 4.0L motor into it (was easier than tearing down the motor in my opinion). I have it running now, but the temperature guage in the dash isn't reading anything?
I broke the old rear temperature sensor off in the block & put a new one from Autozone in yesterday; still nothing. I know that both it & the one in the thermostat housing are connected, so why am I not getting a reading on the dash. The fan kicked on once for about 1 minute right after I installed it, but not since & the block/hoses feel quite warm to the touch.

I am not sure if the sensor was working in the old motor that was in the XJ, I only had it running a little. I know that the old Jeep that the new motor was in the temp guage was working.

Which on controls the guage & which one controls the fan?
I am worried that the fan isn't kicking on & I am overheating the motor - I don't want to mess this motor up right after dropping it in.

The sender in the front (theromostat) sends to the gauge. The one in the rear sends sig to P:CM which turn on fan.

If the guage isn't working then either the front sender is bad, doesn't have ground, or a problem with the wire.

On my 1993 4.0 L it is the exact opposite of what rstarch345 stated !! The sensor at the back of the block (nearest the firewall) drives the gauge. The other sensor at the thermostat housing sends input to the PCM to richen the mixture until you get to optimum temperature. HTH Bill-93XJ

I thought it was the other way around, Front Sensor in the Thermostat Housing signals the PCM and the rear sensor in the head signals the gauge/idiot light.

At least its that way for my 2.5L, perhaps I'm mixing it up and its different for the 2 motors.

"thought it was the other way around, Front Sensor in the Thermostat Housing signals the PCM and the rear sensor in the head signals the gauge/idiot light.

At least its that way for my 2.5L, perhaps I'm mixing it up and its different for the 2 motors."

This is correct. There is a problem with the gauge, or the wiring to the sensor on the back of the block. I opted for a Auto-Meter temp gauge and now my temp never even gets to 210 where it was reading 220-235 all the time on my gauge. It was fairly inexpensive and easy to install the gauge pod on the
A-pillar.
I posted some issues about the temp gauge a while back and got some pretty good responses.
Good luck with the temp gauge.

SORRY

SORRY

You guys are right, hadn't had my morning coffee. Fingers engaged before the brain was warmed up.

No worries, not bashin ya. That's why we're all here.

LABMBA87 said:

"thought it was the other way around, Front Sensor in the Thermostat Housing signals the PCM and the rear sensor in the head signals the gauge/idiot light.

At least its that way for my 2.5L, perhaps I'm mixing it up and its different for the 2 motors."

This is correct. There is a problem with the gauge, or the wiring to the sensor on the back of the block. I opted for a Auto-Meter temp gauge and now my temp never even gets to 210 where it was reading 220-235 all the time on my gauge. It was fairly inexpensive and easy to install the gauge pod on the
A-pillar.
I posted some issues about the temp gauge a while back and got some pretty good responses.
Good luck with the temp gauge.

Click to expand...

So, to confirm - it is the rear sensor that signals the guage in the dash.
That'd mean either a bad sensor (autozone, what more would you expect?) or wiring issue?

jfiscus said:

So, to confirm - it is the rear sensor that signals the guage in the dash.
That'd mean either a bad sensor (autozone, what more would you expect?) or wiring issue?

Click to expand...

Usually, yes. I would recommend using an after market gauge as the resistance variance in the wiring harness seems to be having an issue. I double checked everything at the shop I work at and found that i was getting too much voltage to the sensor at any given time and the gauge was always reading too hot. I replaced sensors in both the block and the t-stat housing. NOTHING. If you can find the wiring issue, let me know please, but considering that this is my daily, and my wheeler, I needed it fixed asap.
BTW, get the sensor from the dealer if you find out it's bad.
Good luck and keep us posted.

I hear that you should go to the dealer for the gauge temp sender....something about the gauge needing to calibrate with a factory sender.

All other sensors seem to work fine coming from auto parts stores....only ones that have problems are the temp gauge senders it seems.