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speedo

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tahoe healey

tahoe healey

Yoda
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Sorry, old stuff again. On a little drive yesterday, the speedo staid at 30 when engine stopped. Disconnected the cable and it stayed at 30 so not angle or cable. Tapped it and it eventually went to zero. Drove it this morning and it registered but sluggishly and inaccurate. It was rebuilt 8 or 9 years ago. Any suggestion as to DIY repair (cleaning)?
Thanks
TH
 
tahoe healey said:
Sorry, old stuff again. On a little drive yesterday, the speedo staid at 30 when engine stopped. Disconnected the cable and it stayed at 30 so not angle or cable. Tapped it and it eventually went to zero. Drove it this morning and it registered but sluggishly and inaccurate. It was rebuilt 8 or 9 years ago.

Any suggestion as to DIY repair (cleaning)?

1]Spray internals with TV Tuner Contact cleaner and blow out with low pressure air.

2] DYS a favor: after 8 or 9 years send to Nisonger for a check up-- :laugh:

Thanks
TH
Click to expand...
 
Surprised you didn't get more response to your query. There was a lot of discussion a year or so ago about problems with new cable assemblies that cause speedometer failures. The inner cable is too long relative to the outer cable putting a thrust load on the speedometer bushing. The bushing (maybe it's a bearing) isn't meant to take a thrust load and is damaged. I can't find the thread now, not even sure which of the too many lists I follow it was on, so I can't tell you what the dimensions should be. Any of the better known instrument shops should be aware of the problem.

As I recall, bad cables were available from most of the popular suppliers.

Marv J
 
The speedo was rebuilt in 2003 and a new cable cut to fit by the speedo shop. I cleaned and monkeyed with it for a week and couldn't get it to stay fixed. I called the shop that rebuilt it and they guessed that the cable had stretched (they say it is very common) enough to force the magnets against the aluminum dish. I kept moving it away but it kept moving back. So, I sent it in to them again along with the cable and they will fix it again (at my expense). I think it is a poor design. There should be some kind of washer between the magnet plate and the aluminum dish as a spacer.But what do I know?
 
I've had my BJ8's speedometer many times so I'm pretty familiar with them. I think if the magnets were contacting the aluminum disk they would peg the needle at 140MPH.

The indicator needle is pressed on a small shaft that is located at the front by two small holes in a brass bracket and at the rear is just rides in a hole in the bracket that holds the driving magnets. There is nothing resembling a bearing anywhere that I can tell. The needle gets returned to zero by a weak watch spring, but that should be enough if everything is moving freely.

The only things I can think of is the needle is getting hung up on the dial face. This could be caused by the shaft getting misaligned somehow. On the front bracket the shaft passes through a bracket that looks something like:


___/___|___\__


(you have to imagine the horizontal bracket across the top)

There is a small brass screw in this bracket that only serves to pinch the two parts of the bracket together. I speculate this is to align the shaft and hence the disk to the moving magnets. I've noticed that cocking the shaft causes the disk to not be parallel to the magnets, and I think this has the effect of 'amplifying' the speed indication.

Don't know if this is any help; maybe someone else can add some knowledge. Even though they are simple in theory these speedos can confound you with their behavior.
 
The needle stops at 20 to 40 MPH every time. I had the speedo apart 3 times this week. If I move the magnet plate away from the aluminum dish the needle rebounds briskly to the pin. The problem is that they will not stay away from contacting each other when the cable is inserted. The worm gear that drives the odometer moves up to the plate and stays there. Out of frustration, I sent it off as I need the car for events scheduled the end of the month. I think a speedo repair should last more miles that I put on in nine years.
I found a Tech Tip in an old Healey Highlights that suggested putting a loop of 24 gauge wire between the worm gear and the bracket to prevent the movement.
Some stuff is just best to be left to the pros.
 
The speedo shop called me this afternoon and indicated that the cable had in fact stretched. He had cut it to fit in 2003. He said this happens a lot. I guess it should be drawn out and measured and inspected every 5 years or so especially if the needle jumps.
 
Any idea how they cut it? The ends of the cable are squared-off--almost molded--and any time I've messed with one I've made a mess out of it and the cable just starts to unwind. IIRC, I tried to trim one with a cutoff tool.

I've seen cables kink, but never seen one stretch. This doesn't compute for me. I heard there were some cables sold a couple years ago that were wound the wrong way; I could see a cable starting to unwind and stretch if that were the case.
 
K
Bob_Spidell said:
I've seen cables kink, but never seen one stretch. This doesn't compute for me. I heard there were some cables sold a couple years ago that were wound the wrong way; I could see a cable starting to unwind and stretch if that were the case.
Click to expand...

I'm with Bob on this. I've never seen a cable stretch and you've had multiple occurrences and have a shop that says it's common. The cable wrapped the wrong way sounds like a plausible explanation.

Marv J
 
A cut off wheel is certainly the way to go if you need to tim the end a little bit.

Beforehand though, you can tin it with solder to help prevent fraying. Don't worry about too much build up, as it is very easily filed back to the original square shape once you're done with the trimming.

I've taken loose several cables/instruments where there was a copper washer between the two; enough so, that now it's a habit to look for one and notice if it's absent.
 
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