[C2] power source
Thread Starter
Burning Brakes
Joined: Jul 2014
Posts: 1,200
Likes: 376
From: Knoxville, TN
2020 C1 of the Year Finalist - Unmodified
power source
I'm tired trying to fix my temp gauge on my 1966 money pit, so my plan is to get a universal one and keep it in the glove box only because i don't want it hanging under the dash.
I know I have 12v power at the radio fuse with the ignition on that can be used for the gauge, but is there any better 12v source. I'm too old to be crawling under the dash to the ignition switch.
I know I have 12v power at the radio fuse with the ignition on that can be used for the gauge, but is there any better 12v source. I'm too old to be crawling under the dash to the ignition switch.
Last edited by Captain Bud; Mar 26, 2026 at 03:06 PM.
Instructor
Joined: Dec 2025
Posts: 219
Likes: 74
From: Pachuta, MS
Since you didn't mention year then it's hard to be specific. If you can get to the fuse panel then you should be able to either find an available switched circuit thatyou might just have to install a fuse to use or piggy-back off an existing circuit at the panel. That's the proper way to do this but the radio circuit will certainly work and I doubt your gauge will add more than a fraction of an amp to the load so no fuse change is needed,
Burning Brakes
Joined: Jul 2019
Posts: 783
Likes: 226
From: Salt Lake City
The temp gauge is such a simple system that it seems to me it might be simpler to fix it than to install another gauge. First, with key on short the sender wire to fround, Gauge should peg. If not, you have bad gauge or wire. Either way you will need a new wire and you can tease out the cluster enough to change the gauge without totally removing it. Good luck
Thread Starter
Burning Brakes
Joined: Jul 2014
Posts: 1,200
Likes: 376
From: Knoxville, TN
2020 C1 of the Year Finalist - Unmodified
I have checked the sender ohms, grounded the green wire, got full hot indication. I really don't want to pull the cluster so another gauge hidden in the glove box is all I need now.
Le Mans Master
Joined: Nov 2015
Posts: 7,442
Likes: 2,620
From: Really Central IL Illinois
The Temp gauge should read max (all the way to the right) when you ground the green wire. Does it read ~100F when you do not ground the green wire and hook it to the sensor?
The sensor on R66 measures 711 ohms when cold (~65F). As the engine temperature rises, the resistance decreases and the gauge receives more voltage and moves upward.
It sounds like the gauge may be good if it moves from cold to hot (left to right) when the engine warms up. What does your gauge do when you warm the engine up to NOT?
IF you want to feed the new temperature gauge from the ignition circuit, the pink wire from the top fuse is switched by the ignition switch. You can select pink wire to the heater, wipers, etc, or use a flag connector from the right side of the top fuse of the fuse box to tie into the circuit.
The radio power wire will also work.
The sensor on R66 measures 711 ohms when cold (~65F). As the engine temperature rises, the resistance decreases and the gauge receives more voltage and moves upward.
It sounds like the gauge may be good if it moves from cold to hot (left to right) when the engine warms up. What does your gauge do when you warm the engine up to NOT?
IF you want to feed the new temperature gauge from the ignition circuit, the pink wire from the top fuse is switched by the ignition switch. You can select pink wire to the heater, wipers, etc, or use a flag connector from the right side of the top fuse of the fuse box to tie into the circuit.
The radio power wire will also work.
Last edited by R66; Mar 29, 2026 at 03:53 PM.
Thread Starter
Burning Brakes
Joined: Jul 2014
Posts: 1,200
Likes: 376
From: Knoxville, TN
2020 C1 of the Year Finalist - Unmodified
I have tried everything. Yes the temp needle moves from cold to hot, ohms checked, good sender ground. I get NO temp indication at all
with a hot engine. The only time I get any reading is during very slow driving with extremely hot ambient temperature. Then for some reason, the gauge works intermittently.
I was driving at highway speed with cool weather and for no apparent reason, the gauge worked.
My idea of using a remote temp gauge won't work. The sender is way to small for a SBC.
Beside my wife, this car is driving nuts.
with a hot engine. The only time I get any reading is during very slow driving with extremely hot ambient temperature. Then for some reason, the gauge works intermittently.
I was driving at highway speed with cool weather and for no apparent reason, the gauge worked.
My idea of using a remote temp gauge won't work. The sender is way to small for a SBC.
Beside my wife, this car is driving nuts.
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Le Mans Master
Joined: Nov 2015
Posts: 7,442
Likes: 2,620
From: Really Central IL Illinois
It sounds like you have a poor connection at either the sending unit or the gauge. With a warm engine, try flexing the green wire as it runs along the engine to the firewall and monitor the gauge. Tug on the green wire where it goes thru the fire wall a bit. Also wiggle the connector at the sending unit and look for a broken wire at the connector.
Then go inside the cabin and see if you can see the pink wire in the bundle. Move the bundle of wires around to see if you get a reading.
If any of these get a gauge fluctuation, you have a bad connection on the gauge or sending unit or a broken wire.
You can walk away when the car is driving you nuts, but it is best to just say YES MAM when the BOSS does.
Then go inside the cabin and see if you can see the pink wire in the bundle. Move the bundle of wires around to see if you get a reading.
If any of these get a gauge fluctuation, you have a bad connection on the gauge or sending unit or a broken wire.
You can walk away when the car is driving you nuts, but it is best to just say YES MAM when the BOSS does.
Race Director
Joined: Jan 2004
Posts: 18,191
Likes: 145
From: Snake handler
It sounds like you have a poor connection at either the sending unit or the gauge. With a warm engine, try flexing the green wire as it runs along the engine to the firewall and monitor the gauge. Tug on the green wire where it goes thru the fire wall a bit. Also wiggle the connector at the sending unit and look for a broken wire at the connector.
Then go inside the cabin and see if you can see the pink wire in the bundle. Move the bundle of wires around to see if you get a reading.
If any of these get a gauge fluctuation, you have a bad connection on the gauge or sending unit or a broken wire.
You can walk away when the car is driving you nuts, but it is best to just say YES MAM when the BOSS does.
Then go inside the cabin and see if you can see the pink wire in the bundle. Move the bundle of wires around to see if you get a reading.
If any of these get a gauge fluctuation, you have a bad connection on the gauge or sending unit or a broken wire.
You can walk away when the car is driving you nuts, but it is best to just say YES MAM when the BOSS does.
Thread Starter
Burning Brakes
Joined: Jul 2014
Posts: 1,200
Likes: 376
From: Knoxville, TN
2020 C1 of the Year Finalist - Unmodified
Temp gauge
You may be right about a loose connection. Only problem is the car has AC and its tough to get to the temp gauge to fiddle with the wires.