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Tstat temp wiring question


NAXJA Forum User
Santa Clarita
Can the Temp sensor from a newer XJ that is located in the Tstat housing be wired to the connector of an older XJ that had the sensor in the rad?
Assuming you have the Renix engine in the XJ, the XJ temp sensor in the housing won't do you any good. The one in the radiator is a N/O thermostatic switch, not really a sensor. The thing to do is either splice a universal switch into one of your radiator lines or there's a switch that went in some 350 Chevy engines that will screw into the thermostat housing.
What are you trying to accomplish?

There are three temperature sensors for your year XJ. The sensor for the gauge (or idiot light) is located on the left (driver's side) rear corner of the head. The sensor that provide data to the ECU for engine controls is located down low on the driver's side of the block, below the manifolds. The sensor in the driver's side radiator tank isn't really a sensor, it is (as noted) nothing but an ON/OFF switch, and all it controls is the auxiliary cooling can.
I was trying to find the easiest way to wire a temp switch to that would control a electric fan to replace my clutch driven one and a newer style aux fan from a later model XJ.

I was planning on putting in a Zirgo 16" to replace the mech fan and clutch.

The Stock T-stat sensor is a resistive element and not a switch. It feeds the ECU which determines when to trigger the fan. You can not use it to turn on a fan relay directly.

If your rig is an '89 your stock fan control is closed loop and does not involve the ECU as do later models with the resistive sensor in the T-Stat.

The best thing you can do (assuming you have an '89) is to get a later model T-Stat housing and put in a temp switch sensor. You can get one from Pianlesw wiring, Hayden, Derale, or us a GM model.. Thats what I did for my '90.
Thanks for the input.

Yes I have an 89, and I picked up a later model Tstat housing when I did my rad conversion. The temps were alot cooler then but now they're starting to heat up and I want to finish my engine cooling project before summer.

Thanks again for the help!