Possible Bad Gauge

[LS Fan]

So I have a 1998 LS400 with 170,000 miles on it. It has been babied and garaged. It is in fantastic shape. One morning this week I started the car, drove about a mile and noticed that the temperature gauge was just under the red line. It normally hangs out just under the halfway mark. I tuned around and drove home as not wanting to run it too hot. Here's what i checked on to determine the issue. Water pump, timing belt, thermostat, all radiator hoses and new coolant was just done 12,000 miles ago. This check out normal. Then I thought that it might be the sensor/sending unit indicating the wrong temperature to display on the gauge. I was going to just buy a new one and change it out, but then I thought of hooking up my OBDII scan tool to check the engine temperature. Sure enough the engine temperature read normal through the real-time scan tool. Here's my logic. If the scan tool shows the correct temperature as read from the ecm computer, it must be getting the temperature sent to it from the sensor correctly which means that there isn't a reason to change out the temperature sensor as a possible fix. I believe that I can rule it out. I think that only leaves me the instrument gauge itself that could be the culprit in this issue. Also, I think that this is the part I need.    CLICK-HERE     

If this is the issue, would it be better to just buy the gauge and change it out or send the instrument cluster in somewhere to be rebuilt?  Also, occasionally the tach sticks at zero so a good slap on the top of the dashboard above the gauge fixes it. Maybe a rebuild of the instrument cluster would fix this too.

Please help me figure out this dilemma. I try to keep everything on the car working at 100% so even if the car isn't running hot, I want the gauge to report the correct temperature. 

[TrevC]

Hi Tim...welcome to the club!

I would agree with your diagnosis of the instrument panel being faulty.

I believe there are issues with the electrical connections having bad joints within the panel itself so maybe consider a complete rebuild of the instrument panel rather than just a component within it.

Let us know how you get on with it

Regards    Trevor - Admin

[LS Fan]

Trevor,  Thanks for the tip. Is there any shop in particular that you would trust your own instrument cluster to be rebuilt by? Also, would you happen to know the correct engine operating temp for this vehicle? I'm thinking 200 degrees?

[Exhaustgases]

Tanin auto electric does clusters.

[TrevC]

Engines usually run at around  190 degrees (88 degrees Centrigrade) which you could measure with an infra-red temperature gun (very cheap to buy nowadays).