Water Temperature Gauge Not Working

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1969VADart

1969VADart

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We finally got my car running and driveable but we have some kinks to work out. The water temperature gauge in the dash does not seem to be working. The car is not having any overheating problems but I don't want to drive it too much without that gauge working. Any ideas what might cause the gauge to not work? Is there a fuse in the fuse block that makes the gauge work or something at the thermostat? Any thoughts would be greatly appreciated.

I hope to get some video of the car running posted in the next few days. Boy does it sound and run good. And that is without the carb totally tuned in right.
 
Does the fuel gauge work?

Try grounding the temp sender wire, turn the key to "run" and watch the gauge. It should "shoot" towards "hot." Don't leave the key on any longer than to see if it works
 
There are some elcheapo senders on the shelves today. A new sender may be all you need. The simple test posted above will tell the tale.
 
I will give this a try and see what I come up with. Much appreciated.

The fuel gauge is not working yet because I have to put the ground strap on the new fuel tank/sending unit. The one that I got when I put the new tank in was a little too short to reach for ground, so we are going to manufacture the ground for the fuel sending unit. Not sure if it matters, but the speedometer works, charge indicator works, and oil pressure light works.

67Dart273 said:
Does the fuel gauge work?

Try grounding the temp sender wire, turn the key to "run" and watch the gauge. It should "shoot" towards "hot." Don't leave the key on any longer than to see if it works
Click to expand...
 
The fuel and temp gauge (and oil gauge, if equipped) all get their power from a device known variously as the "instrument voltage limiter" or "instrument voltage regulator" If that is bad neither gauge will work. This can also be caused by one or more bad connections in the gauge system.
 
This might be a silly question but where is the instrument voltage regulator mounted on the car typically?

67Dart273 said:
The fuel and temp gauge (and oil gauge, if equipped) all get their power from a device known variously as the "instrument voltage limiter" or "instrument voltage regulator" If that is bad neither gauge will work. This can also be caused by one or more bad connections in the gauge system.
Click to expand...
 
Most common location is plugged into the backside of the instrument panel.
 
So I finally replaced the voltage regulator today. And I still have no temperature gauge or fuel gauge working. I also replaced the temperature sending unit and grounded the new fuel sending unit and yet nothing. Also, I replaced all the instrument cluster bulbs and still have no gauge lights. The parking brake indicator light works, speedometer works, ammeter works, and oil pressure light works. Do the parts of the cluster that are not working come off of a single fuse in the fuse block? I am going to go through and replace every fuse tomorrow. Is there a ground or connection that I might be missing? Oh, and taking the entire instrument cluster out was real fun!
 
1969VADart said:
So I finally replaced the voltage regulator today. And I still have no temperature gauge or fuel gauge working. I also replaced the temperature sending unit and grounded the new fuel sending unit and yet nothing. Also, I replaced all the instrument cluster bulbs and still have no gauge lights. The parking brake indicator light works, speedometer works, ammeter works, and oil pressure light works. Do the parts of the cluster that are not working come off of a single fuse in the fuse block? I am going to go through and replace every fuse tomorrow. Is there a ground or connection that I might be missing? Oh, and taking the entire instrument cluster out was real fun!
Click to expand...

Everything that you state is working gets its ground though a wire. Everything that isn't working requires a chassis ground.
 
RedFish said:
Everything that you state is working gets its ground though a wire. Everything that isn't working requires a chassis ground.
Click to expand...

Actually "at least some," certainly solid state IVR requires a ground.
 
67Dart273 said:
Actually "at least some," certainly solid state IVR requires a ground.
Click to expand...

Huh ? I didn't understand your comment. Doesn't matter though.
He will figure out that a metal inst' housing wont play right while dangling from its harness connectors.
He says the speedometer works. How he knows that at this point is puzzling too.
 
I know the speedometer works because I have driven it on the road, and while it has not been calibrated, it seems to be pretty close on the speed reading. I guess I am just at a loss why half of the components (ammeter, oil pressure, speedo, parking brake light) work, but the other half does not. I guess I just don't understand what you mean by dangling from the harness connectors?
 
99% of the time, owners do some inst' panel repairs then power it up for testing before completing the reinstall. That's what I assumed is your case and why.
The housing gets its ground via the hardware that holds it in the dash.
Not everything in the housing uses that ground path. Park brake lamp is grounded by the switch on that mechanism. Oil warning lamp is grounded by that sender, and so on.
Illumination, turn indicators, just about everything does require the chassis ground. Is this making sense now ?
 
RedFish said:
99% of the time, owners do some inst' panel repairs then power it up for testing before completing the reinstall. That's what I assumed is your case and why.
The housing gets its ground via the hardware that holds it in the dash.
Not everything in the housing uses that ground path. Park brake lamp is grounded by the switch on that mechanism. Oil warning lamp is grounded by that sender, and so on.
Illumination, turn indicators, just about everything does require the chassis ground. Is this making sense now ?
Click to expand...

I think I follow. I fully reinstalled the cluster just like I took it out. I will take it back out and trace all the mounts to see if I am missing something. I don't notice anything that seemed out of place but I don't know for sure. Maybe I will try running a direct ground between the cluster and the body and see if that makes a difference. The previous owner had obviously been messing around under the dash because he installed an aftermarket radio.
 
I try to get you guys to think of the gauges as a "complete end to end system" rather than "this works" or "that doesn't"

Here's some of what was wrong with my 67 cluster...............

Power comes to the cluster warning lights and the instrument regulator via "ignition run" from the key through the harness to PC board connector

The harness side of the connector can be loose, broken corroded.

On mine, many of the PC board pins were loose or broken. You can repair them, but mine were so bad that I abandoned the original connector, bought some "Molex" style connectors from Rad Shack and used them. I soldered wire pigtails onto the board traces down below the original pins.

On mine, the IVR was bad, I ordered an RTE replacement.

On mine, the board contacts into which the IVR plugs were NOT making contact with the board traces. I had to solder jumpers from the brass finger contacts to the board traces.

The gauges have "fake nuts" on the gauge studs. Replace these with real nuts and loosen/ tighten them a few times to scrub the connection clean.

Revisit the PC board connector where the sender wiring exits to the harness.

If at all possible, test the cluster out of the car

After reading on this board, I added a dedicated ground pigtail to my cluster, about a foot long, and bolted it to the column support brace

You can test the gauges, temp, fuel, and oil (if equipped) are all the same movement.

Go to RadShack and buy some resistors, you want 11-15 ohms for "full" 23-25 for 1/2 and 70-75 for empty

For example, buy a pack of four 100 ohm, 1/2 watt resistors and wire all four in parallel. This makes a 25 ohms resistor which you wire from either temp or fuel gauge sender to ground, turn on the key, and let it sit for about 1 minute. This should give you 1/2 scale on the guage if the IVR is OK and the gauge is still accurate.

Last don't discount problems in the harness. The temp (and oil if equipped) both go through the bulkhead connector, so THAT is a possible problem. The connector right at the sender can be a problem, and of course the sender itself can be bad or out of calibration

For fuel, the wiring goes through the rear harness kick panel connector, not commonly a problem but it COULD be.

and --------the tank sender must be grounded, and the sender must be correctly operating. Also, it seems that many? most? of these repop senders are not very accurate.
 
1969VADart said:
I think I follow. I fully reinstalled the cluster just like I took it out. I will take it back out and trace all the mounts to see if I am missing something. I don't notice anything that seemed out of place but I don't know for sure. Maybe I will try running a direct ground between the cluster and the body and see if that makes a difference. The previous owner had obviously been messing around under the dash because he installed an aftermarket radio.
Click to expand...

A permanent dedicated ground wire is strongly recommended. Original daisy chain of contact points might have been fine when everything was new but... it never equaled an actual copper wire as a conductor.
45 years later you could take the time to clean every contact surface. Several owners have mistakenly painted over many of those original contact points.
 
you guys need to make a sticky on this issue--- gets asked a lot, Lawrence
 
Look at the back of your cluster. There will be some screws going into the printed circuit board which ground it to the cluster, which is supposed to be grounded through the dash. Use some stake-on's and wire and make a ground lead. Attach one end to the screw I mentioned, and the other to the dash frame somewhere nearby so you can still get the cluster in and out easily. That's been the problem in all my cars, not being properly grounded.

Also, you seem to have it in your head, "why does the speedometer work?" It isn't electric, it doesn't have anything to do with the fuel gauge. It's mechanical, and totally separate.
 
70DartMike said:
Look at the back of your cluster. There will be some screws going into the printed circuit board which ground it to the cluster, which is supposed to be grounded through the dash. Use some stake-on's and wire and make a ground lead. Attach one end to the screw I mentioned, and the other to the dash frame somewhere nearby so you can still get the cluster in and out easily. That's been the problem in all my cars, not being properly grounded.

Also, you seem to have it in your head, "why does the speedometer work?" It isn't electric, it doesn't have anything to do with the fuel gauge. It's mechanical, and totally separate.
Click to expand...

Its not totally isolated though.
Although a ground connection rarely arcs.. if the current does arc through the speedometers mechanical parts or the cable it could screw it up.
There may even be a condition where dc current would demagnetize the gyro in speedometer. Lets not attempt to create that condition. :)
 
70DartMike said:
Also, you seem to have it in your head, "why does the speedometer work?" It isn't electric, it doesn't have anything to do with the fuel gauge. It's mechanical, and totally separate.
Click to expand...

Thanks. I am not really hung up on the speedo, it was just mentioned previously. Since it is cable actuated, I figured it doesn't have anything to do with the immediate problem. I assume there must be a ground issue since all of the cluster lights do not work as well as the two gauges. Going to also go back and check the bulkhead connector as well.

I really appreciate all of the insight from everybody. I can work through body and mechanical stuff, but electrical issues are way beyond my usual skill level. But I did spring for a service manual, so hopefully that will help.
 
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