Instrument gauge diagnosis and repair

[itsdiz]

Subject car - 1965 Barracuda. I have had some issues with skipping speedometer and non functioning gauges so I removed the instrument cluster to see what the problem was. A while back I purchased two used instrument panels to use for parts. My original odometer was missing the plastic gear shaft that turns it so I had used the speedometer from one of the used panels and put my original odometer in to retain the mileage reading it had. This is the one that began to skip while driving. I connected another speedometer cable to the back, and inserted the other end into my cordless drill for testing. After cleaning some gunk out from inside the cable hole on the speedo I think I got it working pretty smooth. As for the gauges, I found this - the ground circuit for the voltage limiter had burned or broken free, so I got my soldering iron out and fixed it, tested the circuit with an ohmeter to make sure it was good. I also had to clean up some of the copper contacts with 0000 steel wool to get a couple of the bulbs to illuminate. Another note, this cluster does not have the condensor on it, I am guessing that it was for radio interference and since this car is radio delete, not necessary.

 

[Murray]

A skipping speedo needle is usually a bad cable.

 

[Dana67Dart]

A skipping speedo needle is usually a bad cable.

it MAY be a bad cable and a cheap and easy thing to test for so it should be test #1, BUT there are other causes as well. There is a "Jewel" (bushing) inside the speedo head that keeps the parts that the needle is attached to in place and centered. when that goes bad with time the ASSY can float and make contact with the rotating magnet that is attached to the speedo cable. When that happens the needle will dance or bounce and many times you can hear an audible click when the needle bounces. and some times at slow speeds you can move the car forward and watch the needle rise off of its resting post and then move back to the resting post.

this is a cross section of the "Jewel" the small ID hole engages with the recess in the speedo needle shaft to keep the needle centered and at the right height.

I just went through this, from replacing the cable to removing and cleaning the speedo head to bringing the head to a proper speedo shop and they explained the entire issue to me. The shop I used had a few more pieces but said when they are gone they are gone as they are not reproduced by anyone currently.

This part is smaller than a pencil eraser. I drew up the CAD and 3D printed some to test fit. the fit seems right but my material is not sufficient. Its on my back burner.

The OEM parts are swedged in and replacements are epoxied in. I toyed with a c clip

 

[RustyRatRod]

Nice repair. I wouldda set the whole damn thing on fire trying to solder it. It probably wouldn't hurt to maybe coat that solder joint with some clear coat to seal it. Maybe just brush a little on. Some clear fingernail polish would do it.

 

[itsdiz]

it MAY be a bad cable and a cheap and easy thing to test for so it should be test #1, BUT there are other causes as well. There is a "Jewel" (bushing) inside the speedo head that keeps the parts that the needle is attached to in place and centered. when that goes bad with time the ASSY can float and make contact with the rotating magnet that is attached to the speedo cable. When that happens the needle will dance or bounce and many times you can hear an audible click when the needle bounces. and some times at slow speeds you can move the car forward and watch the needle rise off of its resting post and then move back to the resting post.

this is a cross section of the "Jewel" the small ID hole engages with the recess in the speedo needle shaft to keep the needle centered and at the right height.

I just went through this, from replacing the cable to removing and cleaning the speedo head to bringing the head to a proper speedo shop and they explained the entire issue to me. The shop I used had a few more pieces but said when they are gone they are gone as they are not reproduced by anyone currently.

This part is smaller than a pencil eraser. I drew up the CAD and 3D printed some to test fit. the fit seems right but my material is not sufficient. Its on my back burner.

View attachment 1716491601

The OEM parts are swedged in and replacements are epoxied in. I toyed with a c clip

View attachment 1716491603View attachment 1716491604

Great information, I've never fully understood how they work. I am planning to run the car in gear with the wheels off the ground and watch the cable to make sure it is spinning freely. The original speedo seemed to work okay so if need be, I'll swap parts back to the old one, which is probably what I should have done in the first place.

 

[Dana67Dart]

Great information, I've never fully understood how they work

This is the location on the needle drive that the "jewel" locks on to

This is a prototype of a jewel

this is the Jewel, Needle drive, clock spring assembled

 

[itsdiz]

This is the location on the needle drive that the "jewel" locks on to

View attachment 1716491888

This is a prototype of a jewel
View attachment 1716491890


this is the Jewel, Needle drive, clock spring assembled

View attachment 1716491891

Interesting, I have never taken one apart that far. I am going to check mine once again before I reinstall the cluster, but it seemed that the drum portion - for lack of proper terminology - was bouncing before I cleaned out the gunk and got better afterward, not sure if that was the issue or what you are showing. Thanks for the info. I do have a spare brand new cable also.

 

[Dana67Dart]

Because anything that contacts the needle drive and the spinning magnet (attached to the speedo cable) will cause needle bounce or other issues

Cleaning out the areas CAN help, there can also be metal particles stuck to the magnets.