Hello again, Hoping to get this ironed out somehow.

While driving one day I noticed that my coolant temp gauge suddenly pegged all the way hot and is now stuck there, even when the engine is cold. It is not overheating, runs between 180 and 190 degrees (verified with an infrared thermometer). I suspected a faulty sending unit at first, as I would disconnect it and the gauge would go back down over time. However when I installed the new one it did the same thing as soon as the key was turned on - Spiked hot and stayed put. Most likely a short in the circuit somewhere, but I don't want to start guessing and change more parts out to find that I've wasted money....

Anyone have this issue randomly occur before? I'm hoping someone else has found an answer so I at least have a direction to look into.

Looking forward to hearing your feedback!

Thanks!

-Zack

 

Iirc, That equation only has two variables... the unit itself and the green wire that runs from it all the way to the wire harness connected to the gauge cluster.

 

Open the hood. Look on the driver's side exhaust manifold or header. You're looking for the green wire, or the wire formerly known as green that is likely melted to the exhaust. Or look for where the green wire is pinched and is grounding. If all that is good, take a good long look at the gauge itself and see if the needle is hanging up on the edge of the gauge face - it happens.

 

I'm guessing it's a wiring issue, already had the dash partially disassembled to inspect the gauge and it moves freely...

Thinking I have to look into the harness itself and see the condition of the wire. Nothing that is directly visible indicates that there is a problem.. Plenty of clearance between the wire and the exhaust, and none of the insulation is missing. Have to open it up and trace the wire to the gauge.

 

FWIW the temp gauge on my '89 LB( 305 IROC Z was stuck, pegged hot. I installed a new gauge and it reads fine. Approx. 15 accessible screws and the cluster lens, trim and gauge pull right out.