Speedometer: what the heck is going on?

[Acollin]

1966 series V stock setup

I just came back from a drive and now my speedometer is acting nutty. Mileage counter and trip Odometer seem to be OK , but the needle appeared to spin all the way around and stick there underneath the stop pin when the car is moving. I stopped at a traffic light and while not moving the needle reads about 35 mph. I start up again the needle spins clockwise back to the stop.

I assume the cable is working. I am hopeful that one of you wizards has seen this behavior before.

Thanks in advance for the help
Andrew

 

[alpine_64]

I would think the cable might be binding. Did the needle bounce before it jammed? Take the cable out of the speedo and slowly drive and put your finger on the end of the cable drive and feel if it is flicking or catching.

If so.. Remove the speedo cable and slide it out of its casing clean and lubriacte with a lithium grease then slide back in and reinstall

 

[hartmandm]

Odometer and trip odometer are direct gear driven. Speedo needle has magnetism involved. I would guess a lubrication issue in the speedo. I'd suggest you disassemble the speedo, clean everything, and lubricate the things that should be lubricated.

There are a couple of articles on speedo rebuilds on my site that give the details for disassembly, cleaning, and lubrication. Go to the "Gauges" section of the page to find them.
http://wp.mhartman.net/home/cars/sunbeam/alpine/info

Mike

 

[hartmandm]

Agree with Michael to check cable for binding. With the speedo sitting at 35 when the cable isn't spinning, you have to remove the speedo and fix it.

Once you have the speedo disassembled, cleaned, lubed, and reassembled, you can test the speedo behavior using a variable speed drill. I believe a slotted driver bit will fit nicely into the cable input connection on the back of the speedo. Spin the speedo cable input connection counter-clockwise using the drill.

Mike

 

[Acollin]

The needle is not stuck but moves in an odd range.

Car not moving-- speedo reads about 35 mph
Car moving--- as far as the needle can go clockwise , off the grid back to the pin

The needle may have had a " bounce" before it went wacky. I noted something in the corner of my vision, but when I looked again, it was pegged as far as it could go clockwise.

I guess my plan should be to pull and lubricate the cable and check. I won't take the guage apart unless lubricating the cable doesn't help.

Thanks-- I will post what I find.
Andrew

 

[Ken Ellis]

While you're addressing the cable, it's good to have it secured at multiple points along the way so it can't whip around. Whipping can cause unsteady displayed speed, but this is an 'incidental' recommendation. I don't think cable whipping or movement can actually cause the main problem you're seeing.

(Side note: I have a Chevy Suburban that had a speedo recall issue. It would run more as a 'totalizer', displaying the top speed achieved, never going to zero. Next time you started the truck, it would add your new speed to the old total, and then stay there. Didn't take long before you were doing 130 while stopped.)

 

[George Coleman]

One note do not!!!! lube the cable!!! I know believe me !!

 

[Tom H]

If it is not at zero when the car is stopped you MUST go inside the speedo and see and fix what's up. NOTHING about the cable would cause the needle to stick. There should be nothing but air (and a light magnetic field) between the magnet driven by the cable and the cup that the needle is connected to. Something (fragments of the gasket?) has gotten into the space between the magnet and the cup. You may also have a cable problem, but that is secondary. Click on the link Mike Hartman provided and go to the Gauges section and click on the Speedo to see what's inside.

Tom

 

[Barry]

If it is not at zero when the car is stopped you MUST go inside the speedo and see and fix what's up. NOTHING about the cable would cause the needle to stick. There should be nothing but air (and a light magnetic field) between the magnet driven by the cable and the cup that the needle is connected to. Something (fragments of the gasket?) has gotten into the space between the magnet and the cup. You may also have a cable problem, but that is secondary. Click on the link Mike Hartman provided and go to the Gauges section and click on the Speedo to see what's inside.

Tom

Nail hit on head with sledgehammer. The cable has nothing to do with what the speedometer does when the car is not moving.

 

[husky drvr]

Andrew,

Wild guess is the spring that returns the needle to zero is broken.

 

[mikephillips]

as noted the speedo needle is driven by a magnet. The way it works, the shaft has a magnetized disc on the inside end which sits inside a shallow cup, without touching it, which is driven by the cable from the transmission. The shaft rests in a nylon type "bearing" at the back end of the speedo. As the car speed increases the magnet spins faster and the cup on the end of the needle shaft is pulled clockwise against a circular spring. The spring keeps the shaft from moving all way around when pulled by the spinning magnet and returns it to zero when the magnet stops spinning. So, a couple things can happen to mess this up. One as noted is the spring could have failed or come loose. A second is that the nylon bearing or shaft end could have failed causing the alignment of the cup/magnet to shift and they are now actually touching and grabbing each other. Only way to know for sure is to disassemble the gauge. If the shaft bearing has failed and the cup/magnet assembly is rubbing on each other, you won't be able to fix it at home since the magnet has probably been damaged and will no longer be the same size and shape as before which affects the pull on the cup. The spring you might be able to deal with, but remember you'll need to careful what it is replaced with since if the tension of a replacement is too high or too low, it will affect how it reads.

Good luck.

 

[Acollin]

Thanks for all the help-- everyone. Great explanation, Mike.

As always, I could use some advice.

1) If I send my speedo out to a service, what should I expect to pay?

2) Which makes the most sense: to buy a used speedo from a reputable parts seller or have my speedo rebuilt?

Be well all
Andrew

 

[mikephillips]

A lot of people use these guys.

http://www.nisonger.com/

Now I never have, so I have no personal opinion good or bad about what you get from them.

As for rebuild or buy used, keep in mind all the original used instruments are 50 years old or older and until opened up you don't really know the condition of what you're getting. Anything you buy may soldier on for years or suffer a breakdown next week. Considering that I'd probably have a rebuild done, provided it was rebuildable since I don't know the availability of all the bits and pieces inside one.

 

[Tom H]

I suggest you take it apart and look inside. It might be as simple as a chunk of gasket stuck in the cup. If you elect to buy a used one, be sure to get one with the same calibration you have now - see the number on the dial at the bottom edge- probably 1020 for a stock SV.

Tom

 

[65beam]

speedometer

Nissonger does good work. They were in the business when the cars were being sold new. There service charge isn't cheap but the quality is great. They converted the cable driven tach for one of my Harringtons to an electronic unit. Cost was somewhere around 460.00 give or take a couple dollars. That included restoration of the face, housing, etc. Repair of the speedo is probably less. Call them and ask for the cost. You could always set your GPS on the dash and have a really accurate speedo reading. I do that all the time. The speedo wasn't real accurate when the cars were new. I picked up a few speeding tickets for that reason back in the late 60's and early 70's.

 

[Rick Young]

Nisonger repaired my TR speedometer a few years ago. It still works perfect. I think it was $110.00.
Rick

 

[Acollin]

I emailed nisonger yesterday. They replied quickly. I asked for an estimate and relayed my symptoms.

They quoted $175 + shipping and provide a 1 year warranty. They say they set them up to a factory spec .

Given the cost I see for used, the service makes sense. Hard to believe even the most reputable seller of used parts will stand behind a used guage for a year.

I will open it up to have a look to see if I can make sense of it. I do not believe my tinkering will effect much if I decide to go the rebuild route.

Andrew