[ajftj]

What a great write up from JJ, some useful info in there for me to try on my 04 TJ, always wondered what the actual temperature is compared with the needle position.

I was thinking about your problem and trying to understand what kind of electrical issue would give those symptoms (assuming nothing else has changed) and couldn't really come up with a good theory. To go straight to 100 with key on, youd need a low resistance between the connected module and ground. If the sensor was still connected in parallel but functioning the gauge would be higher than the expected value. The two resistances in parallel would create a slightly lower resistance, so a slightly higher temperature. Then when the actual sensor heated up as its resistance fell, the gauge would eventually start to read too high - but you said it reduces a fraction after warm up.

Its hard to imagine what could happen to the sensor during a flush, but who knows.

Id start by disconnecting the sensor, leave the wire hanging and start the engine. In my TJ this brings the engine management warning lamp on, because it detected a failed sensor and it's an emissions fail. Don't panic after the 4th engine start with it reconnected the fault self heals.

In your case if there is a damaged wire but your module still sees a resistance which equates to 100c approximately, the gauge will read ok, the warning lamp wont come on and you will have to focus on the wiring.

On the other hand, if you get an engine warning lamp (stays on when running) and your gauge is stuck cold then id have to assume for some reason a sensor, or less likely, grounding problem. If you wanted to get a bit more scientific in this scenario, pop into Jaycar and buy a 1.2Kohm resistor, hang it on the end of the connector between the two pins gently. And expect to see about 80c on the gauge, proving your diagnosis of the sensor before you buy one.

But overall, ask yourself what you might have physically disturbed, bumped, crunched or pulled during the other work.

A bit generic, but interested to know what you eventually come up with.