Coolant temperature sensor on 1991 XJ

My temperature gauge is no longer working, so I suspect it is the coolant temperature sensor. But I see two on my Jeep. One is in the thermostat housing, and one looks like it is located on the intake manifold near the firewall on the driver's side. I do not have an electric cooling fan on this Jeep - looked like it never came with one, this is a Jeep that was also sold with no A/C. Which sensor do I need to replace to get the gauge working? Thanks in advance.

Found it. I kept looking for the type like on the thermostat housing with two wires and the plug in type connector, not the bar type one.

and??? where was the sensor?

- The one on the drivers side of the motor, in the head, near the firewall is the sending unit for the dash gauge or idiot light, depending on your gauge gluster.

- The one at the front of the motor, near the thermostat housing is for the ECU to monitor engine temps.

In later years, they eliminated the separate gauge sensor and used just one sensor at the thermostat for both the gauge and the ECU.

The sensor was at the back of the head, just looked like a threaded rod. I found that the wire was disconnected from the sensor. Reconnected it, and the gauge is now working. The Jeep is new to me, so I'm just working through issues.