Erratic speedometer operation

[mike kerley]

My speedometer has been erratic the last few trips. Jumps around, sometimes dead, sometimes not. I'm guessing the sender has a coat of nice black oil on it. Any suggestions on where to locate this cookie before I crawl under the beast with my spray cans of brake clean and disposable clothing?

8V92.

[Jon Wehrenberg]

Mike,

If it is the original it is likely to be in need of replacement.

I ended up replacing the speedo on both of my coaches. I didn't even bother to see where the sender was on my current bus but on the first one it appeared to be a magnetic sensor picking up the signal off the front wheel. (my memory ain't so hot so take that with a grain of salt.)

The replacement has an LCD display for the odometer and doesn't click like the original. The time to switch them out was about 20 minutes to a half hour.

[Petervs]

Mike, your speedo is electric, no greas or oil involved.

Seems like the early 90's vintage ones are all failing. Prevost now sells a newer VDO version, it is more robust electronically.

See my earlier thread "Speedometer was kaput" for details on how I solved my broken one. You may be able to do similar.

You can also buy them cheaper if you shop around. Here is one example:
http://cgi.ebay.com/ebaymotors/VDO-437152-Speedometer-Vision-Series-0-85-mph-3-3-8_W0QQcmdZViewItemQQcategoryZ33678QQihZ012QQitemZ2 20383611348QQrdZ1QQsspagenameZWDVW

This is the same thing Prevost sells. You can program it electronically to read exactly correctly, a simple process.

Hope this helps. A fun weekend project if you like to tinker.

[mike kerley]

Thanks Jon and Peter, I'll try that first. Its not nice crawling around under there.

[merle&louise]

Question: Will the new speedometer record the old mileage and add current miles to it? Or is it going to start from zero! Should Mike keep the old speedometer?

I changed an hour meter on my boat, it was a mechanical VDO gauge, and I kept the old gauge to substaniate the total hours on the engine. The fellow that purchased the boat from me appreciated the fact that I kept the old gauge.:D I know that the Pro Driver records the mileage, but I was just wondering how the electronic speedometers work.

[Jon Wehrenberg]

The new speedo can record the correct mileage, buit as Peter posted it requires a signal generator to do so and you can only program it at an 85 MPH rate. I have service log books and I recorded the Detroit Pro Driver mileage, plus speedo mileage with each entry and I logged when the speedo was changed so there is documentation. Unless the Pro Driver and the new speedo both puke simultaneously there should be no issue in reconstruicting my coach's actual miles, which BTW are meaningless because there are so few relative to its potential life.

[Petervs]

A speedo shop can send the new one in to be electronically programmed for about $125. I balked at this fee and devised a way to do it myself.

It is intentionally designed to be difficult to change the mileage so when a vehicle is sold it can then be relied on to be an actual mileage.

[0533]

My speedometer has been erratic the last few trips. Jumps around, sometimes dead, sometimes not. I'm guessing the sender has a coat of nice black oil on it. Any suggestions on where to locate this cookie before I crawl under the beast with my spray cans of brake clean and disposable clothing?

8V92.
Mike, I was having an erratic speedometer as well. It would go crazy off and on, showing weird numbers etc. This was all going on when I was having the voltage issues. After changing out all of my Chassis batteries it has never happened again. Might be cheaper if the speedo is bad.