What causes speedometer to fail (1 Viewer)

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Finally got my '71 running and moving on to some of the smaller details like the speedometer. The obvious issue was no speedo cable. Ordered a new one from Specter and installed it yesterday but still no go.

I pulled the cluster to check the speedometer itself. I can spin the magnet with a drill, the needle is free and connected to the cup around the magnet, but no movement of the speedo needle with the drill. Odo works fine. What could be wrong with this thing? Can the magnet go bad?
 
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Could be stripped gears inside the speedo housing. They are plastic and develop cracks over time.

If you tear it apart, replace those gears and that still doesn't fix the problem, then your speedometer drive gear in the tail of the transfer case could be stripped. That's my next stop with mine.
 

bj40green

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Finally got my '71 running and moving on to some of the smaller details like the speedometer. The obvious issue was no speedo cable. Ordered a new one from Specter and installed it yesterday but still no go.

I pulled the cluster to check the speedometer itself. I can spin the magnet with a drill, the needle is free and connected to the cup around the magnet, but no movement of the speedo needle with the drill. Odo works fine. What could be wrong with this thing? Can the magnet go bad?

He said that the speedo needle doesn't move but that the odo works fine so..... the problem is in the unit but where?????
I don't have a spare any more but from memory it works like this:
In the top right corner is a little gear that separates the turning of the cable into the speedo and the odo movement.
Check this for old sticky grease.

Rudi

Edit: Here's a picture "How it works"
DSC06652_text.JPG

Can you turn the disc with the holes in it by hand? This should turn with almost no force because it's a magnetic coupling. If not.... remove the needle, pull it off and attach a tiny drop of WD40 to the shaft.

Good luck,

Rudi
 
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This is what I'm looking at, pre 9/72 or whatever. The central dark part spins with the cable. The needle is connected to the silver piece just to the outside of that. And yes the piece connected to the needle is free.

1410453592876.jpg
 
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There isn't much to it. If the magnet spins but the needle doesn't move, then there is no magnetic coupling. Check the magnet.
 
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He said that the speedo needle doesn't move but that the odo works fine so..... the problem is in the unit but where?????
I don't have a spare any more but from memory it works like this:
In the top right corner is a little gear that separates the turning of the cable into the speedo and the odo movement.
Check this for old sticky grease.

Rudi

Edit: Here's a picture "How it works"
View attachment 940606
Can you turn the disc with the holes in it by hand? This should turn with almost no force because it's a magnetic coupling. If not.... remove the needle, pull it off and attach a tiny drop of WD40 to the shaft.

Good luck,

Rudi


Rudi and Pih_head,

I'm attempting to revive an old thread. We spoke a few years ago re-rebuilding the odometer, you may remember though I'm sure just about every guy with a Cruiser has contacted you with the same issues. So I see in this thread you speak a little about the speedo itself and not the odometer. I have two speedos now where the odometer works but not the speedometer. They don't appear to be stuck anywhere. One doesn't appear to be coupled to the magnet...the magnet will spin from the cable connector side and I can move the needle by hand which turns the metal disc inside the housing. It appears the magnet is no longer strong enough to drag on the disc to which the needle/spindle is attached. Does this make sense? Is this a case of the magnets just "wearing out"? The disc that the needle spindle is attached to, inside the housing, appears to be aluminum and is not attracted to the magnet. The housing that it sits in IS attracted. I don't know the physics of this but somehow a force must be created and the aluminum disc sort of gets caught in the storm, causing it to spin. So, if indeed it's the magnet that has gotten weaker over the years, is there any kind of fix?

My other unit does spin the needle but it is completely erratic and makes a grinding sound that changes in volume as the needle gets up into the 80/90 mph (I'm doing 30 or 40 maybe). Any clues on that one? Do we just chuck these units at this point, or rather, just use them for an odometer and resign ourselves to the speedo never working again?

Thanks, Sproggy
 
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Sorry, its a 2nd gen cluster, I believe. Fits a 1971 so the screw on type cable....
 
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If you want to know how they work, Google "eddy current speedometer".

If you want to know what is wrong, you will have to take it apart. They are very delicate.
 
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Sorry guys, somehow I missed the replies here until now. I actually got one of them working. It seems it just needed lube. Yes, they are delicate and the eddy current is really not strong at all. So any bit of friction caused by a non-lubricated drive shaft seems to be enough to prevent proper functioning. I was reading up on magnets going bad and that does indeed happen over time, especially with heat so years under the dash in a hot climate could ruin them? I didn't actually run across any time frames or temps in regards to a magnet losing its force. The other unit I was working on, well, I thought maybe the magnet was indeed bad but then I noticed that the drive shaft where it goes through the speed cup (hmm, now I'm a bit foggy…where it goes through one of the elements) seems to be a bit wobbly as if some sort of bearing is missing or worn and thus it rubs at this point and creates enough friction to prevent the cup from spinning. At that point, I was eager to get the other unit installed and put it aside for a rainy day. The only problem I seem to have now with the unit I have installed is that it reads 10 to 15 mph too fast. I assume I just need to spin the needle on the drive shaft counter-clockwise X amount.

It's a fascinating little mechanism. Seems like a pretty wacky way to make a speedometer but what do I know? I would think a few years of wear on that hair spring and the accuracy would start to change….
 

David70FJ40

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Had the same problem in my '70 40, speedometer made funny noises and worked poorly when connected to a drill. I realize this will not satisfy the purists but I replaced it with a GPS speedometer from Auto Meter. No cables, no fuss, very accurate.
 
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Had the same problem in my '70 40, speedometer made funny noises and worked poorly when connected to a drill. I realize this will not satisfy the purists but I replaced it with a GPS speedometer from Auto Meter. No cables, no fuss, very accurate.

Interesting…I didn't know they made such things (I'm pretty out of the loop). Got a pic of it? I'm interested to see where/how it's mounted. I'm not a purist myself. I quite like to find work-arounds to things. This is perhaps out of necessity i.e. lack of funds.
 

David70FJ40

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Again, I realize the purists here will not like this but my speedo and gauges were toast/junk. So I looked around for the easiest option I could find. While watching one of the auto auction show the commentator said the hot rod that was on the block came with a GPS speedo which made bells go off in my head. I already had a replacement speedo which required another cable and a pulse generator which had to be calibrated. Looked like to many places for something to go wrong so I found the Auto Meter GPS speedo. Love it. Easy to wire in and the antenna can be mounted anywhere with its magnetic base.

DWS_1197.JPG


Sharp eyes will see the antenna wire in front of the speedo, that is now well hidden and the antenna is on the hood. I also added LED lights in the gauges which makes a ton of difference at night.
 
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Wow that sure is different looking. Who fashioned the face plate so well? Ammeter...just run without one?
 

David70FJ40

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The face plate came from BTB Products but I am sure there are others who have something similar as well. The gauges can be purchased from almost any speed shop and I believe Auto Meter will sell direct as well. The water temp, oil pressure and volt meter have been moved to the dashboard and were rewired when the new wiring harness was installed. I was told the volt meter does a better job and I wasn't able to find an amp meter anywhere. Here is what the speedo looks like now and the gauges on the dash.
GPS Speedo.JPG
Dash Gauges.JPG
 
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…that takes some getting used to! I feel lost looking at it, weird, eh? I'm so habituated to the more or less stock placement and look of everything...
 

David70FJ40

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Understand. I have never been one to go by the book and have always looked for the different and unusual. I want to put my individual touch on this 46 year old truck and make it as individual as I can. Wish you the best for yours.
 
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…I get where you're coming from. I rely on rust for the "individualization factor." All kidding aside, I agree with you. I'm not looking for a hot rod. I'm looking for a car with character and story and plenty of dings and dirt enough where I don't have to worry about it. I don't like perfect. I do like functional.

It's good to know that these gauge options are out there. Cheers David, Sproggy.
 

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