While in the middle of a timing belt change on the 88 240 my wife came in with a speedometer story on her 91 745t. Seems the speedometer registers zero while under way with an occasional jump up towards the probable speed only to slowly roll back down to zero again. The odometer and trip odometer are still registering. I didn't see a similiar description in the FAQ's. Has anyone encountered this? If so what was the fix? I am assuming something internal to the speedometer head and wondering if it is linked to an electrical fault or mechanical. Thanks

Randy

The same thing happened to my '86 740 GLE a few years back... I was told it was the receiving unit ( the actual speedo itself). $$$

I was lucky enough to find a whole new instrument panel with almost the exact same Kilometer reading.... 5-10 mins to replace and you don't get dirty! :) Only cost me $100 CDN


Andy

I am under the impression that it is somewhat harder to remove the cluster in 91+ 740's. I am currently avoiding the issue.

What is involved in removing the cluster on yours? Evidently not much if the repair that was that quick!

Randy

On the '86 740, the cluster is removed by popping out 2 covers on the lower right and left corners of the cluster. There is a screw behind each cover. The cover on the lower left of the cluster is associated with the clock adjustment knob. I don't remember what the lower right side has... mine may have nothing. Can't remember. The 91 is probably different.
I haven't had a chance to look over the one I just bought ( 91 940 ), since I'm dealing with a bigger issue with that one ( toasted engine), plus it's not within walking distance at the moment.

A very small slot screw driver is handy for popping out these covers/bezels.

Incidentally, I sort of blame myself for the speedo going dead.... I used to reset the trip meter after filling up... and once I did it while driving and that's when the speedo went haywire.... I don't know if that was the cause... but I certainly won't try it a second time!

Long winded reply noted... hehe... but do be careful with the connections on the back of the cluster if you do it yourself... even scarier things may happen if you're not.

Andy

Randy,

Have you solved the problem? My speedo acts similar. It will sit at zero until I'm going around 60 and then it will shoot up to 85. If I drop below 60, it goes back to zero. My odometer and trip counter work fine.

Thanks!

I was able to acquire a used 140mph speedometer to swap in on this car but have not gotten around to doing it yet (I seem to maintain a small fleet). I am hoping to locate a suspect solder joint when I pull the original one and I will try resoldering it before using the other one. I want to keep my original odometer reading and don't want to have to explore changing the odometer setting.

Randy

Randy,
I had the same problem about a week ago, turns out to be the speedometer sensor on the rear differential. There is more in depth info here:

http://www.brickboard.com/FAQ/700-900/ElectricalInstruments.htm#Speedometer_Failures

hope that helps out some :)
steve

Steve,

Thanks for the response. That entry in the FAQ's indicates the odometer quits at the same time as the speedometer. Ours is only effecting the speedometer; the odometer and trip odometer are still working correctly.

Randy

My speedo was jumping around at idle. I replaced the speedometer and it fixed the prob. 700 instrument clusters seem to have probs. On my 90 740 I have to smack the dashboard almost everytime i drive to get the voltmeter and gas level guage to even work.