MGB & GT Forum

I have been having a strange issue with the speedometer in my 1969 GT. The odometer works fine, but the speedometer will do one of several things:

- It will stick at 20 mph - regardless of actual speed. Moving the speedometer cable while stopped will return it to zero. Until the next time I drive past 20 - then it gets stuck again.
- Speedometer needle will not move at all - regardless of actual speed. Moving the speedometer cable will get the speedometer working for a short time.
- Speedometer will read 20 to 30 mph over actual speed. Moving the speedometer cable while the car is in motion will get the indicated speed back to actual.

Everything was working fine before I removed the dash this winter. I installed a new speedometer cable back then.

One thing I noticed is that the speedometer will operate fine with the dash out and the car running on jack stands. When I put the dash (and speedometer) back in the speedometer stops working. I thought maybe there was a tight curve in the cable behind the dash so I bought a right-angle adapter. That has not helped the situation that much.

I also thought maybe I had a bad new speedometer so I got my spare from the parts box - same issue.

Throughout all this the odometer continues to work so I need the speedo is getting revolutions from the cable. It baffles me as to why pushing/pulling the cable gets everything working again.

Before I send the speedo to the guys at Palo Alto is there anything else I can check? I can't be the first guy with this issue.

Did you change to LED bulbs when the dash was out? sometimes, if the bulb is pushed too far in, it can cause the needle to hang.

I did! That would explain why it works with the speedo out of the dash.

Heading out to the garage.......

I reached up and pulled the bulb out 1/8". Took it for a drive around the block and - the speedo is working perfectly.

THANK YOU!

Glad I could help! my local lbc mechanic suggests putting a small o-ring (available in most hw stores) around the bulb socket, to keep it from pushing in too far...