Speedometer cable issues?

[Jerry]

Question for the forum. My speedometer quit a while ago and I determine that the 90 angle drive was gone. I happened to have an extra so installed it. That also went bad. I cannot turn the cable by hand which seems strange to me. I am wondering if it got kinked. Should the cable turn by hand? It does turn with a drill.

Thanks

Jerry
BJ8

 

[Keoke]

Hi Jerry yes the cable should turn quite freely by hand.
I suggest you remove the core and have a look at it. If it appears good without any fraying I would then look for a kink or a pinch in the outer cable sheath. It may also be that the speedo has packed in.--Fwiw--Keoke

 

[Jerry]

I had the speedo repaired by Palo Alto Speedometers, but that does not mean it is still working. I am going to discounect it and try an old cable that I have in the barn. Maybe it will tell me if it is the cable or the Speedo. I find sometimes thinking about the problem overnight gives me an option.

PS: I had earlier told you guys my car was overheating (new engine). I have a 123 electronic distributor. Someone on the Healey list recomended a profile of 8 for the distributor. That turns out to give too much advance. I changed it to profile B. Now it runs like a Healey! Lots of power and the heat went away.

Jerry
BJ8

 

[Jerry]

I think I may have found the problem. I took the Speedo out because I could not get it to turn by hand. I put a bit that looks like the end of the cable into the back. Too stiff to turn. This does not seem normal? What do you say?

It will turn with a drill. That tension is putting too much strain on the other parts of the system.

Jerry

 

[Rob Glasgow]

Jerry, I had the same problem with my BT7 two months ago. The angle drive broke, I repaired it, it broke again, replaced it with a new one and it broke. All broke within a few feet of operation and all of them twisted a the short piece of cable that enters the overdrive. Finally pulled the speedo and found that it turned very stiffly. When I took the speedo apart, I found the worm gear that is driven by the cable was binding on the gear that turns the odometer. I couldn't see a reason for the binding, but there were some brass shavings present. The speedo would turn, but the binding caused too much stress on the angle drive.
I replaced the speedo with an old one I had laying around. I repaired the angle drive and put everything back together. So far everything has worked for 300 miles.
As a side note, I installed a 3:54 rear end last year and afterwards the speedo always read incorrectly. When I replaced the broken speedo, I attempted to recalibrate it by installing the needle in the "minus 5 MPH" position. I then carefully flexed the needle over the resting pin to put it one the left side of the pin at zero MPH. I was pleasantly surprised to find the speedo in now actuate (within 1 MPH) at all speeds from 10 MPH to 70) based on a comparison to my GPS. Several friends said "adjusting" the needle this way would not calibrate the speedo over the entire range, but only at one speed. Although that make sense to me, my testing shows it's correct at all speeds. Can anyone explain why resetting the needle can work over the entire speed range?

 

[TimK]

Not me!

 

[Rob Glasgow]

Just to make myself clear, resetting the speedo needle only fixed the MPH reading, but the odometer and trip meter are still off by 8%. Also confirmed by comparing to GPS I think that is to be expected based on switching from a 3.9 to 3.54 gears.

 

[Bob_Spidell]

I've done a lot of work and study on my speedometer. As far as I can tell, there is no adjustment for the speed reading other than changing the initial position of the needle (also indicated in the well-traveled speedo guide by Anthony Rhodes). Generally, mechanical/magnetic speedometers are only accurate at one speed or in a narrow range; if yours is accurate from 10-70mph you are fortunate.

Your tripmeter and odometer will be off (low) approximately 11% (3.91/3.54). The 'cure'--besides a ratio change box on the cable--is different driven gears on the tripmeter and odometer. Palo Alto Speedo did mine when I installed the 3.54 rearend--over $200 and a couple weeks to get the gears.