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Discussion Starter #1
I am having a heck of a time trying to figure out what is wrong with my stock console temp gauge in my 68 Camaro. It steadily creeps all the way to hot in a matter of 5 minutes. I pretty much ruled out an overheating problem. So far I replaced the sending unit with a "calibrated" unit from lectric limited. I tested the thermostat. I replaced the wiring from the sended to the bulkhead in the engine compartment. I tested the temp gauge with a potentiometer and got these values:

Cold: 172 Ohms 9.5 Volts
1/4: 95 Ohms 7.2 Volts
1/2 78 Ohms 6.7 Volts
3/4 66 Ohms 6.2 volts
Hot 47 Ohms 5.2 Volts

I also measured across the upper and lower posts on the gauge itself and it read 88 Ohms. I also checked the grounds on the gauge itself and they are clean and tight.

Any help would be appreciated.

Thanks!
Mike
 

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Mike68RS,

I had a similar problem with my 69 Temp Gauge, I changed both the sensor & gauge without any success.

My problem was that when I was staring the engine, the Temp Gauge was reading full scale when the dash light was coming on.

Make sure that the Dash Temp Light & Ignition Switch (the one that tests your dash lights) are out of the circuit.

In my case the light is out and I cut (problem solved) the Ignition Switch wire going to the Dash Temp Light.

To make a long story short make sure that your Temp Sensor is Directly connected to the Temp Gauge.

Here’s an extract from the console gauges installation procedure, hope this will help you.

Good Luck,
Daniel.


TEMPERATURE GAUGE.

1967
UNPLUG THE SPEEDOMETER CLUSTER PLUG FROM THE REAR OF THE SPEEDOMETER CLUSTER. THE PLUG IS NUMBERED ABOVE EACH OF THE 12 INPUTS. LOCATION 2 CONTAINS TWO DARK GREEN WIRES. DISCONNECT THESE WIRES FROM THE PLUG AND TAPE THEM ASIDE. ORIGINALLY ONE OF THESE DARK GREEN WIRES WAS ROUTED TO THE FUSE BLOCK AND THE OTHER TO THE IGNITION SWITCH. TRACE THE DARK GREEN WIRE TO THE FUSE BLOCK AND DISCONNECT IT FROM LOCATION C-Z. TRACE THE OTHER DARK GREEN WIRE TO THE IGNITION SWITCH AND DISCONNECT IT ALSO. THIS PROCEDURE NOW REMOVES THEORIGINAL DASH TEMPERATURE LIGHT CIRCUIT FROM SERVICE. CONNECT THE DARK GREEN WIRE FROM THE GAUGE HARNESS CONNECTOR (LOCATION 11) TO FUSE BLOCK LOCATION C-2. THIS NOW ROUTES THE TEMPERATURE LEAD DIRECTLY FROM THE FUSE BLOCK TO THE GAUGE HARNESS CONNECTOR.

1968
UNPLUG THE SPEEDOMETER CLUSTER PLUG FROM THE REAR OF THE SPEEDOMETER CLUSTER. THE PLUG IS NUMBERED ABOVE EACH OF THE 12 INPUTS. Location 2 CONTAINS TWO DARK GREEN WIRES. DISCONNECT THESE WIRES FROM THE PLUG AND TAPE THEN ASIDE. ORIGINALLY ONE OF THESE DARK GREEN WIRES WAS ROUTED TO THE FUSE BLOCK AND THE OTHER TO THE IGNITION SWITCH. TRACE THE DARK GREEN WIRE TO THE FUSE BLOCK AND DISCONNECT IT FROM LOCATION C-T. TRACE THE OTHER DARK GREEN WIRE TO THE IGNITION SWITCH AND DISCONNECT IT ALSO. THIS PROCEDURE NOW REMOVES THE ORIGINAL DASH TEMPERATURE LIGHT CIRCUIT FROM SERVICE. CONNECT THE DARK GREEN WIRE FROM THE GAUGE HARNESS CONNECTOR (LOCATION 11) TO FUSE BLOCK LOCATION C-T. THIS NOW ROUTES THE TEMPERATURE LEAD DIRECTLY FROM THE FUSE BLOCK TO THE GAUGE -HARNESS CONNECTOR.

1969
LOCATE THE TWO DARK GREEN WIRES GOING INTO THE TEMP LIGHT (SECOND LIGHT FROM THE RIGHT IN THE LIGHT ASSEMBLY LOCATED TO THE RIGHT OF THE STEERING WHEEL). DISCONNECT THESE WIRES FROM THE LIGHT SOCKET AND TAPE THEM ASIDE. ORIGINALLY ONE OF THESE DARK GREEN WIRES WAS ROUTED TO THE FUSE BLOCK AND THE OTHER TO THE IGNITION SWITCH. TRACE THE DARK GREEN WIRE TO THE FUSE BLOCK AND DISCONNECT IT FROM LOCATION C-T. TRACE THE OTHER DARK GREEN WIRE TO THE IGNITION SWITCH AND DISCONNECT IT ALSO. THIS PROCEDURE NOW REMOVES THE ORIGINAL DASH TEMPERATURE LIGHT CIRCUIT FROM SERVICE. CONNECT THE DARK GREEN WIRE FROM THE GAUGE HARNESS CONNECTOR (LOCATION 8) TO FUSE BLOCK LOCATION C-T. THIS NOW ROUTES THE TEMPERATURE LEAD DIRECTLY FROM THE FUSE BLOCK TO THE GAUGE HARNESS CONNECTOR.
 

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A sensor / guage mismatch can cause this. Also, grounding problems may also cause a misread. Mesure the voltage potential between the engine block and guage ground to see if there is a bias of more than a couple tenths of a volt.
 

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Discussion Starter #4
Well after wasting my time removing the gauge and wiring it directly only to have the same symptoms, a friend of mine gave me a clear radiator hose to check for coolant flow and I also removed the thermostat to find that the temp stayed cool. I previously tested the thermostat and it opened o.k. I again checked it after i removed it to try the clear hose and again it appears to open. I haven't put in a new stat yet, but it does seem like the stat is causing my problem
. Mybe it is only partially opening and I assume its opening all the way.I will put in a new one tomorrow and let you know the results.

Thanks!
Mike
 

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Did you just add this gauge cluster, or did it just star doing this recently?

Sounds like you don't have a ground on the rear gauge mounting panel. It doesn't show on any wiring diagrams but you need a ground jumper that runs from the front panel to the rear panel. I forget which gauge mounting panel you actually connect the ground lead that attaches to the transmission tunnel (think it's the rear one with the temp gauge), but you need to place a jumper from one panel to the other. If you don't the lamps on the ungrounded panel won't light up, and the temp gauge will creep all the way to H and stay there, or the fuel gauge will stay pegged at F depending on which one isn't grounded.

There are no grounds on the gauge connections themselves. The case is grounded to the rear guage mounting panel thrug the lower mounting stud. If you have a ground connection added, anywhere but there that will be a problem in itself.

http://home.townisp.com/~markcanning/camaro/gauge1.jpg
http://home.townisp.com/~markcanning/camaro/gauge3.jpg
 

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Discussion Starter #8
The problem just started on day and the cluster was in and working from the day I got it about 22 years ago. Normally the gauge will read between a quarter and the halfway mark. I removed the gauge from the cluster and wired it directly to 12v to the battery, ground from the bottom post and to the sender, so I know it's most likely not a wiring/ground problem. Again, I changed the sender, the stat, tried new wiring, the pump seems
good, I have new hoses and an aluminum radiator.
Today I am going back out there with a thermocouple that I am going to put in the upper hose right after the stat to get a true reading of the water temperature and compare it to the gauge. I am thinking it's the gauge since there's not much left!

Mike
 
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