It started yesterday afternoon, usually mine reads 3 mph more then I'm driving. Now, every time i start the car to drive it changes. This morning it is reading 10 mpg less than it is going. Last night it was read 3 mpg less than I was driving. Anyone have this problem before?

Thanks

The gears slip on their shaft. Very common problem. New or used speedos are available and a search will reveal methods of repair if you want to try that route.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Make sure you fill up the tank when it reads 3mpg more.

You get better fuel economy that way.

Problem was the battery. I have been told you need a good battery for a Mercedes Diesel but wow, I didn't expect this to happen.

I was mistaking not a battery problem. This is happening again. I'll be driving along when all of a sudden it will drop down 10 t0 20 mph and not come back up to accurate speed. Any ideas?

Thanks

__________________
1983 300SD Turbo

The W126 has some plastic gears that disintegrate after a number of years. there is a couple places the make the new gears for replacement.

There is a difference between the Diesel and Gas as far as the gear count on teeth of the gears.

W126 speedometer gears

Odometer Gears - WELCOME

http://www.odometergears.com/documentation/Mercedes-Benz_Electronic_Odometer_Repair.pdf

Diesel only
Mercedes W126 (diesel only) Odometer gear repair set



Installation guide
Garagistic - BMW E30 and NISSAN S30 motor swap specialists - VDO e30 odometer repair instructions

W126 odometer gear repair kits - Benzworld.org - Mercedes-Benz Discussion Forum



Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

since your speedometer signal is electric like mine (1983 300sd) look for electrical problems
loose grounds, broken ground wire etc
just fixed an erratic temp gauge by cleaning connections. electricity with out a consistent ground is trouble.

only the ODOMETER is affected by the gears. the speedometer is driven off an electric signal motor drive, on a slip ring to the needle... the problem is either in the motor or the signal... I 2nd ground and connection problems.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Still having this problem. Anyone fix this problem? There are times when it works perfectly and other times it will fail when driving or not work correctly at all.

__________________
1983 300SD Turbo