Temp gauge stuck on Hot (key on or off)

[ChuckN]

I know there’s been many posts on temperature gauges, but just wanted to ask that if my temperature gauge reads on hot all the time, and I know if there is power getting to the sensor, then it is likely the gauge? I know it is getting power to the sensor through the wire because I accidentally dropped the wire on the intake manifold when I was trying to reposition it and it sparked and not just a little bit. I’ve just started down this road and I have errands to do today, but thought I would check in here before I start buying parts for it. Thanks in advance! I’m not wholly inexperienced when it comes to wiring, but sometimes I am a little bit rusty and don’t understand the rationale, so please feel free to be elaborate it’s only one wire, so I’m guessing it’s grounded through the intake manifold.

The set up I have has the temperature sensor inside the gooseneck where the thermostat is. I just replaced some gaskets, and put some sealer on the threads of the temp sensor when I put everything back together so perhaps that is keeping it from grounding? SBC 350 for reference. I find it concerning that if it is a ground problem (too much sealant?), then it seems like the gauge would go back to cold when the key is off?

 

[Ricko1966]

Sounds like you have something wired wrong or just the gauge has physically stuck. Tap the face of it. Any gauge if every seen was key on,hot to gauge. Gauge to sender,sender to ground. I'd want to know why that gauge has constant power.

 

[ChuckN]

I think the gauge might be stuck. Key on or off, it doesn’t even waiver, not even a little bit. Do these gauges go bad sometimes?

All other gauges seem to be just fine.

 

[ChuckN]

I hate throwing parts at it, but out of time saving, I ordered a new sensor and went ahead and got a temp gauge from LMC (wanted one anyway since it has actual numbers on it rather than H or C). They’re all 40 years old now and doesn’t hurt to replace. Failing that, I’ll get in and dig around when I put the LMC tach kit in- need to replace a bulb or two while I’m at it and assess why the gear indicator above the steering column doesn’t work. It’ll be a minute since I’m knee deep in doing a complete brake rebuild from head to toe but I’ll get there.

 

[ChuckN]

Sounds like you have something wired wrong or just the gauge has physically stuck. Tap the face of it. Any gauge if every seen was key on,hot to gauge. Gauge to sender,sender to ground. I'd want to know why that gauge has constant power.

Hey, just discovered something- completely stumbled upon it. I was checking something with the carb and had removed the ground wire from the electric choke on the Edelbrock and I happened to notice that suddenly the temp gauge corrected itself to cold.

Reconnected the ground wire and then directly back to pinned on Hot. So I disconnected the ground wire again from the choke, and ran a test wire from the ground terminal on the choke directly to battery ground, and the temperature gauge went back to cold. Also ran test lead from the ground terminal on the choke to the ground screw on the carb (bypassing the choke wire) and temp gauge also goes to cold there as well.

Clearly the choke ground wire that goes to the carburetor is bad, so I will replace that. But why would it go pinned hot when the power is hooked up to the choke and doesn’t have good ground? Is it trying to find ground through the temperature gauge wire in the intake manifold?

 

[Ricko1966]

Hey, just discovered something- completely stumbled upon it. I was checking something with the carb and had removed the ground wire from the electric choke on the Edelbrock and I happened to notice that suddenly the temp gauge corrected itself to cold.

Reconnected the ground wire and then directly back to pinned on Hot. So I disconnected the ground wire again from the choke, and ran a test wire from the ground terminal on the choke directly to battery ground, and the temperature gauge went back to cold. Also ran test lead from the ground terminal on the choke to the ground screw on the carb (bypassing the choke wire) and temp gauge also goes to cold there as well.

Clearly the choke ground wire that goes to the carburetor is bad, so I will replace that. But why would it go pinned hot when the power is hooked up to the choke and doesn’t have good ground? Is it trying to find ground through the temperature gauge wire in the intake .

Get a schematic and check wire colors and locations. The wire going to the electric choke should be a hot not a ground,and grounding a gauge is exactly what makes them peg. Chase your wiring and give us a pic of your electric choke complete with wiring so maybe we can see what's going on.

 

[ChuckN]

Ok will do- I’m out of the house now, but I will definitely grab a photo later and post it up.

But yes, wire going to electric choke is hot (I tested it). Just has a small squiggly ground wire that is going from the negative terminal on the electric choke on the Edelbrock carb that goes to the carb body itself for grounding.

 

[ChuckN]

Found this old photo- I cropped it in. You can see the small black ground wire that is disconnected from the electric choke and the power wire that is connected. When I bought the truck, that ground wire was already disconnected. I had connected it up, not knowing any wiser, and this is probably why it was disconnected from the get-go. When I put a temporary wire in its place, it grounds fine, and the gauge goes back to normal. So clearly there is a breaking that wire internally somewhere.

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