too cold or inaccurate gauge?

I have only owned my XJ (87 4.0) for a few months and the temp seems to stay right around 170 or so. I have only seen it above that a couple of times when wheeling. I assumed that the PO put in a lower temp thermostat so I went and got a 195* one from the dealer. Well, the one I pulled out was 195* and the temp didn't change with the new one.
What do you think?
Is my sensor/gauge just inaccurate? If so, am I getting into the closed loop or does that come from a different sensor?
TIA

It just may be the sensor that is bad. I think you can just unscrew the sensor and place it in some hot water to see if it reads. Use a thermometer to use as a reference.

I think all that should work, but just guessing. I would check the sensor first. On my '96, I think the sensor for the gauge was on the back side behind the valve cover and not the one that is hooked in by the thermostat.

Just a guess

In boiling water (not resting on the bottom of the pan) the temp sender's resistance should be 185ohms (slightly higher for lower boiling temps) --

A 1.5K ohm resistor should get your guage to read 100*F

The temp gauge and t-sender are really touchy in the area that the XJ operates (like 1.5Kohms is 100*F, 450ohms is 160*F, 185ohms shoud be about 212*F) - so a little variance in that area can make a significant change to the readings/indications ..

Since the meter is really measuring current - voltage regulation plays a huge role as well...

... It's not a scientific value, but it's a good measure of what's hot and not -- changing the sensor is really your only affordable option - then you'll likely end-up with what you have already...

Plus the senders don't cost all that much from the dealer anyway. I think my temp sender was around $25.

Tom Dennis

Well, I had the same problem, actually mine stays in the blue zone, on the left of the scale. New temp sending unit didn't solve it.

So, I took the gauge out after I warmed the engine to operating temperature and played with the resistance at the back of the gauge. I think an 180 Ohms one make it point to the center. It looks as if it works OK now, across the whole band.

Mine is a 1984, maybe the years take their toll on the resistance?

Rgds