Speedo drive

You don't legally have to have an operating speedo in your country? (USA I guess)

Plus if your speedo don't work then you're not recording mileage are you?

My speedo needle bounces at very low speeds, almost as if only a couple of teeth on a gear working...

Any comments for Mac or I?

Al

Um, he's trying to fix it, isn't he? But, the law is "don't speed", having defective equipment will add to the penalty, maybe, but isn't something you'll get busted for in and of itself. If you use, for instance, a GPS to keep from speeding, I don't know of any states where anyone would care.

That'd be a good troubleshooting step. Is the odo working, or are they both broke? If both are broke, it's between the tranny and the instrument. If miles are rolling on the odo, but the speedo doesn't move, it's the instrument itself.

There's no gear, it's a needle in a drag cup. Kinked cable can give you what you describe, and if it goes long enough it will also damage the instrument. Been there, done that.

Dave Hinz

That kind of thing varies by state in the US. If your state requires an annual inspection, you'll probably need a working speedometer to pass. If your state does not require an annual inspection (for example, my state requires an inspection only when the car is first registered, and then an emissions test every 2 years), I don't see how anyone would ever know whether your speedometer is working.

John

If it's a mechanical speedo, then it'll be the cable that's either duff or curved too sharply somewhere.

Cheers,

Colin.

according to other sources, the speedo is cable driven and the flat rate for changing it is about 30 min. therefore, I conclude it is not a big job and will give it a try when i get a cable.

You do, but nobody ever checks, I'd certainly want it to be working though.

Me too, surely there's a US equivalent of the UK M.O.T. test?

Al

I'm pretty sure the speedo isn't checked on the MOT - at least not for cars.

It is required for type-approval though, so manufacturers have to fit them.

Cheers,

Colin.

Of course. You can only continue to drive your car if you show the proper...payment. Pay for your plates, you're good to go. In high population counties and surrounding counties, you also have to pass emissions testing annually. And if you have defective equipment, you can be pulled over for it, or if a cop wants to inspect your car on the side of the road when they have you stopped for something else, they can and do.

Dave Hinz

How can they check the speedometer while standing still? The policeman is going to run alongside while you're moving? [Some of them could use the exercise.]

Not in Washington state anyway, they test every 2 years for exhaust emissions but nothing else, you can get a ticket if you get pulled over having a light out or something else visibly defective but there's no inspection for any of that stuff.

Cable, as far as I know. All C900 speedo's are driven the same way.

You need to check a few things. The speedo cable is driven by a special gear setup coming from the transmission, and the cable has a square shaped plastic 'driver' that slides into the 'socket' at the back of the speedo itself to transfer rotational energy the mechanism inside the speedo gauge.

It's possible that the gearing to drive the cable inside the transmission has failed, or the cable isn't properly connected at the back of the speedo (the special spring clip may have broken). If you ever get the dash apart and can watch the dash-end of the speedo cable while driving, watch to see if it rotates. If not, the gearing in the transmission is probably faulty or the speedo cable itself has been kinked or somehow has corroded internally.

If you see the dash-end rotating, make sure the small square-shaped 'driver' piece is intact and hasn't broken itself. If that's ok, check that the cable was properly attached to the back of the speedo gauge with the special spring clip that secures it.

If that is all ok, then the speedo gauge itself is most likely faulty. The gear to drive the odometer might have cracked and got jammed against the worm gear that comes from the speed part of the guage, or something else could have broken internally.

I looked into getting speedo's repaired some time last year and it's surprisingly difficult to locate places that repair VDO's mechanical speedo gauges, at least here in Australia.

Good luck working out what the problem is though - let us know if we can help some more.

Regards,

Craig.

They can't, they don't. Doesn't matter. It's your responsibility to have a working, accurate speedometer. If your speed is wrong and you get a ticket, defective equipment _adds to_, rather than excuses, the fine. So, "Sorry, my speedometer is broken" would be a bad thing to say if pulled over. Just a different approach; your laws assume anyone with a bad speedometer is a problem, ours only fine those who actually do something wrong.

Me, I wouldn't drive without knowing (accurately) how fast I'm going...

It is it is also a precaution, if your car is technically OK there is less of a risk that you will cause damage to others.

and if you do, they will sue your ass off for damages.

-- MH '72 97 '77 96 '78 95 '79 96 '91 900i 16