This connector has a clip that holds it in place on a bracket, and I thought this was the ground you were referring to in your last post.

--tj

 

So, if a disconnect the right plug that you mentioned, it should never reach H, but stay of C? Then what?

 

Did the gauge remain at C when you unplugged it?

 

The behavior remains unchanged, i.e., it starts at C and after starting, 10 seconds later, clims to H.

 

If you unplugged the sensor I labeled with the yellow arrow, then there is either a problem with the wire from that sensor to the instrument cluster or you had two clusters with the same problem?

I would reinstall the old cluster, because the lights work on it. When you unplug the old cluster, you will want to test that the wire in question has an open circuit to ground when it is unplugged at the sensor on the engine.

 

Thanks for the pix, after I unplug the wire, it doesn't move at all from C. Once the wired is plugged it, it slowly rises to H after idle for 10 seconds.

This is with the new cluster.

 

Then you need to replace that sensor. It is called something like the coolant temperature sending unit.

 

After replacing the "coolant sending unit sensor" nothing has changed. I'm suspecting the cable itself is the culprit. Any new ideas?

--tj

 

Unfortunately my idea isn't all that good...

The gauge staying zero when it's unplugged, kinda shows that the wire isn't shorted to ground. The gauge climbing high shows the wire isn't open. So that leaves a faulty gauge.

Sure you got the right sending unit??

When testing, the shop manual warns that you shouldn't allow the gauge to peg at HOT. But I don't know how the gauge behaves if you allow it to do that.

 

I replaced the sensor sending unit. It was the same sensor that you pointed in the picture. The old cluster was re-installed, but the same behavior. Actually, the old cluster slowly climbs to normal temperature, and then shoots to H and bounces from H to normal while driving, most of the time it's stuck on H.

Not sure what's next.

--tj