MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Speedos, not swimwear

My speedometer, which has not been functioning properly since buying the 1974.5 mgb roadster last year, has stopped working all together. Prior to its complete failure it would sort of wave back and forth around the 40 mph mark no matter how fast I was going. I am not sure as to where to begin and don't want to buy angle drives, cables, etc. when that might not be the problem. The odometer and trip odometer are still working but not all that accurate (miles recorded are about 30% less than actually driven, this was the way it was when I purchased the car). The only thing I did to it was to change the chrome bezel to the proper one for its year and in so doing did touch the speedo needle, after that it didn't work at all. As to the cables in the rear of the gauge, the one in the center is tight (I assume that is the speedo cable). The cable near the edge is somewhat loose and I can't seem to tighten it down (again I am assuming that is the odometer cable). Any ideas as to which way to proceed?
John

Hi John
First of all you have to do some trouble shooting to establish which part of the system has failed. A lot of times it is just a broken cable. And I am a firm believe in start trouble shooting with the easiest accessible components first.
Jack the car up and securely support it. Undo the speedo cable at the tranny. Get yourself in a position where you can see the speedo and still give the cable a few turns (you will have to figure out which way to turn it). If the speedo and cable are working then the needle will move a little when you turn the cable. If the needle doesn't move then up under the dash pull the speedo cable off the speedometer, yes it’s the center one. Pull the cable out to see if it is broken. If it is not broken, lubricate it and re-install it. Take a look at the driven gear in the tranny. It isn’t that hard to get at and see if the gears are stripped. If not put it back in. If the speedo is still not working at this point, then you know everything else is ok. It has to be the speedometer. Perhaps a speed shop in your area can fix it or you can locate a used one.
If you do need a used one, take a look at the bottom of the speedo face itself, see all the little white numbers there at the bottom, the used speedo (or new) will have to match those numbers.
Hope this helps.
Bruce


Bruce Mills

Hi John.

Given that it stopped working when you changed the bezel I suspect that you may have bent the needle a little so that it drags on either the glass or the dial.

It does sound as if it has an internal problem too, which might be cured by cleaning and lubing the internal bearings, but this is delicate work and may be better left to someone with experience.

There was a thread about this recently.

Don
Don

John, there is only one cable, and as the first step I would unscrew it at the speedo and pull it out so that you can see the end. You should have half an inch of the inner cable stcking out, and if all is well on the cable side you'll see this spin if you drive the car a few yards.
Steve Postins

This thread was discussed between 02/01/2006 and 03/01/2006

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.