Temp gauge issues.

[76chevyc20454]

I have a 1976 K10, when I got the truck the temp gauge only went up to the 1/4 mark so I put in a mechanical temp gauge. The waterpump failed so I put a newer radiator, waterpump t-stat and hoses. The t-stat I pulled out was a 180, so I put in a 195 to get my heat working again. I figured that was the reason the factory gauge only went up to the 1/4 mark. I went ahead and put a new sending unit in and the same thing happened. When I ground out the wire for the gauge it jumps all the way up to hot, but I can't seem to figure out what's going on. I checked ohms at the sending unit and it read 150 ohms. Need some advice please.

 

[chengny]

I have a 1976 K10, when I got the truck the temp gauge only went up to the 1/4 mark so I put in a mechanical temp gauge. The waterpump failed so I put a newer radiator, waterpump t-stat and hoses. The t-stat I pulled out was a 180, so I put in a 195 to get my heat working again. I figured that was the reason the factory gauge only went up to the 1/4 mark. I went ahead and put a new sending unit in and the same thing happened. When I ground out the wire for the gauge it jumps all the way up to hot, but I can't seem to figure out what's going on. I checked ohms at the sending unit and it read 150 ohms. Need some advice please.

Maybe the factory gauge is indicating the coolant temperature correctly. By how many degrees does it differ from the mechanical gauge you were using? Did you ever have a chance to run them side by side? You aren't using teflon tape to seal the sender threads in the head are you? That can raise the resistance across the sender and cause the gauge to skew lower than it should read. Check that your t-stat is properly seated in the intake manifold so that no coolant is able to leak around the outer edges of the flange.

 

[76chevyc20454]

Maybe the factory gauge is indicating the coolant temperature correctly. By how many degrees does it differ from the mechanical gauge you were using? Did you ever have a chance to run them side by side? You aren't using teflon tape to seal the sender threads in the head are you? That can raise the resistance across the sender and cause the gauge to skew lower than it should read. Check that your t-stat is properly seated in the intake manifold so that no coolant is able to leak around the outer edges of the flange.

My old gauge read 220ish so I thought it might be messed up because it read 200-210 with a 180 t stat and 220 with a 195. I had it in my truck before and it read 210 with a 180 t stat. I don't think its overheating, the radiator cap hasn't sprayed coolant out and the hoses are hot but you can hold your hand on them. It may be reading correctly but I'm going to take the teflon tape off just to make sure and see what happens. Thanks for the input

 

[highdesertrange]

I just posted this chart on the other temp thread,

http://www.gmsquarebody.com/threads/temperature-gauge-reporting-wrong-temp.21751/

highdesertranger