'70 C10 Temp Gauge Max Hot, Why? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**c30** · 01-31-2024, 10:43 AM

Had a similar thing happen once after I changed the cab on a 72 pickup.
Temp gage would go full hot when key was in the start position.
Problem went away after I installed the ground straps from engine to cab and from cab to frame.
Was the gage carrying the full ground to the cab? I don't know.

**CKfan** · 01-31-2024, 01:20 PM

Hooked the sending unit wire back up, the battery, turned the key to on and quickly pegged the needle again. Reversed what I had done but this time touching the back of the terminal and tapping on it had no effect. Still pegged.

Bad ground seems likely but everything else on the cluster works.
I have two ground straps to the cab already, as I know to use lots of grounding points on these trucks. Because the dome light doesn't work also, I will take off and re-tighten the ground straps to see what happens.

**1970cstblazer** · 01-31-2024, 01:50 PM

In other GM forums, guys have had issues with the currently available sending units, as the resistance values are not the same as original. Only AC NOS or Lectric Limited reproductions are correct to get a somewhat accurate reading.

https://www.lectriclimited.com/catal.../category/734/

**CKfan** · 01-31-2024, 02:21 PM

Quote:

Originally Posted by 1970cstblazer

In other GM forums, guys have had issues with the currently available sending units, as the resistance values are not the same as original. Only AC NOS or Lectric Limited reproductions are correct to get a somewhat accurate reading.

https://www.lectriclimited.com/catal.../category/734/

The new one I installed was just over the counter at Napa. So that could be the issue. So many variables.........

**HO455** · 01-31-2024, 02:36 PM

The circuit works so when the wire is off of the sensor the guage should read low. When the wire to sensor is grounded to the block the guage should peg high and it should be some where in between when hooked to the sensor. The key must be on for these tests.

If you get no action then I would check the continuity of the wire from the sensor to the guage plug at the circuit board disconnect the sensor from the wire for this. If you have good continuity then I would pull the guage. It is possible to just remove the temperature guage pair from the rest of the guages. Possible not easy.

01-31-2024, 10:43 AM	#1
c30 Junior Member Join Date: Feb 2015 Location: chicagoland Posts: 30	Re: '70 C10 Temp Gauge Max Hot, Why? Had a similar thing happen once after I changed the cab on a 72 pickup. Temp gage would go full hot when key was in the start position. Problem went away after I installed the ground straps from engine to cab and from cab to frame. Was the gage carrying the full ground to the cab? I don't know.

01-31-2024, 01:20 PM	#2
CKfan Senior Member Join Date: Nov 2022 Location: So central coast, CA Posts: 393	Re: '70 C10 Temp Gauge Max Hot, Why? Hooked the sending unit wire back up, the battery, turned the key to on and quickly pegged the needle again. Reversed what I had done but this time touching the back of the terminal and tapping on it had no effect. Still pegged. Bad ground seems likely but everything else on the cluster works. I have two ground straps to the cab already, as I know to use lots of grounding points on these trucks. Because the dome light doesn't work also, I will take off and re-tighten the ground straps to see what happens.

01-31-2024, 01:50 PM	#3
1970cstblazer All stock and staying that way Join Date: Jul 2003 Location: Elkland, PA Posts: 1,400	Re: '70 C10 Temp Gauge Max Hot, Why? In other GM forums, guys have had issues with the currently available sending units, as the resistance values are not the same as original. Only AC NOS or Lectric Limited reproductions are correct to get a somewhat accurate reading. https://www.lectriclimited.com/catal.../category/734/ __________________ 1970 K/5 Blazer CST 4WD, Bronze, 93k ACT. miles, 350, 4 speed, positraction, 16.5" x 8.25" wheel option, tilt, tach, vacuum, AM/FM, manual throttle...Dad ordered and purchased new 4/70. Currently frame off restoration in progress... 1972 Cheyenne Super 20 2WD, DK Blue/White, 90K ACT. miles, 402, TH400, 4.10 open, tilt, tach, vacuum, A/C, AM/FM, manual throttle.. A mostly original paint never rusted Texas survivor... 2017 Sierra 1500 SLT 4WD, Black, 41k miles, 5.3, 6L80E, 3.42 LS, 20" polished wheels, everything but moonroof and 6.2... 2019 Canyon SLT 4WD, White, 60k miles, 3.6, 8L45, 3.23 LS, 18" wheels

01-31-2024, 02:36 PM	#5
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 10,948	Re: '70 C10 Temp Gauge Max Hot, Why? The circuit works so when the wire is off of the sensor the guage should read low. When the wire to sensor is grounded to the block the guage should peg high and it should be some where in between when hooked to the sensor. The key must be on for these tests. If you get no action then I would check the continuity of the wire from the sensor to the guage plug at the circuit board disconnect the sensor from the wire for this. If you have good continuity then I would pull the guage. It is possible to just remove the temperature guage pair from the rest of the guages. Possible not easy. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377



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