Hi guys I have an 86 chevy c10 with a carbed 5.0 liter my problem is that intermittently the gauge just goes nuts all the way around to way past 260 back to nothing and everywhere in between then without warning it just goes back to normal. I know the problem is either in the gauge or the sending unit my question is can the sending unit cause this. Second where is the sending unit for the gauge located. Any help would be appreciated. By the way the truck is not actually overheating and the coolant level is good.

As for the question of "can" the temperature sending unit cause this condition? Absolutely.

As for the location, it is usually mounted on or near the upper radiator inlet nipple where the large upper most radiator hose attaches to the engine. A vehicle manual will point out the exact location. You can either purchase one for approximately $20 at any auto parts store or go to your local library.

Thanks for the response I already have a haynes manual for it but the manual wasn't very clear the wiring diagram showed the sensor but the location was not stated at least not that I could find this truck has two sensors one for the computer and one for the gauge. I did finally locate it through a little hands on troubleshooting its on the driver side just below the exhaust manifold. The clip holding the wire away from manifold had broken and allowed the wire insulation to melt allowing the bare wire to ground out occasionally. Wire is repaired as of today and all is well thanks again. AC

Generally speaking, when something electrical that was working starts acting funky, it's a short or loose connection. Those sensors are pretty basic, so they don't go out very often. I'm glad you found it. I am amazed that the Haynes wiring diagrams are still in black and white. I had a manual for one of my Ford trucks that had them in color. What a time saver. Before I retired, I ran construction crews on occasion and there was never enough time and money to do the job right, but there was always enough money to do things over. Go figure ?

They list the color of the wire in the diagram but it's a very basic schematic broken into about 6 or 8 different sections I think part of my problem is that 86 seems to be a crossover year I think it was the last year for the carbed models before they went to the throttle body injection. Any way thanks for the interest and your right a full color diagram would be awesome. Have a good evening. AC