VDO Speedometer needle bounces

Melbo · April 10, 2016, 06:55:24 PM

We drove to Rock Point for a week of sunshine and on the way home the speedometer needle began to bounce and not show a consistent reading it was not over reading the speed but under reading by about a fifth. The tachometer worked fine but reads from the motor so I know it was not a voltage fluctuation. I thought at first that maybe a magnet was knocked off the wheel. I did not get under and check BUT the cruise control runs from the same set of magnets and it worked fine. The speedometer reads from four magnets on the drivers side front wheel. NOW for the question. Is the speedometer (it is a VDO 24 volt electronic unit that was new about 5-10 years ago or so) worth sending in for repair or just get a new one and don't bother with the old one because it will be more trouble and money to try and get it fixed. Any thoughts would be appreciated before I pull it out to send it in.

Thanks

Melbo

DoubleEagle · April 10, 2016, 07:36:45 PM

If it is possible, price it both ways. If it is close, go with a new one. I have had good luck with IssPro models.

luvrbus · April 10, 2016, 07:50:28 PM

Mel,if it was me I would toss the wheel driven speedometer and go with a new VDO driven off the transmission with a impulse generator www.precisionspeed.com he can repair it or sell you a new unit

oltrunt · April 11, 2016, 09:25:15 AM

If that is a cable driven speedo, try greasing the cable--a cheap fix that often works. Jack

luvrbus · April 11, 2016, 09:35:16 AM

It may not be the head the pill box gives a lot of problems with age that is why I just go the route of the pulse generator off the transmission 2 twisted wires to the head and your done

bigred · April 11, 2016, 03:50:27 PM

Could be as simple as a loose ground also!!

Melbo · April 11, 2016, 04:54:55 PM

I have a twisted pair to the sensor by the front wheel. The magnets that the speedo reads are the same ones the cruise uses.

Melbo

lvmci · April 11, 2016, 05:29:10 PM

Hi Melbo, there are new speedos that are GPS self contained units, look and read just like traditional speedos, I think just browsing I saw some 24V uniits, they are not connected to anything but a wire antenna, tom, lvmci...

DoubleEagle · April 11, 2016, 05:35:28 PM

Quote from: lvmci on April 11, 2016, 05:29:10 PM
Hi Melbo, there are new speedos that are GPS self contained units, look and read just like traditional speedos, I think just browsing I saw some 24V uniits, they are not connected to anything but a wire antenna, tom, lvmci...

I have one on my 84 Eagle. It is totally dependent on the GPS signal, but you do not have to worry about senders or gear ratios or tire sizes. It also runs the odometer as well.

gumpy · April 12, 2016, 06:19:38 AM

First, check the bolts in the brake drum. There are either 2 or 4. Make sure one hasn't come out. Then make sure the hall effect sensor is positioned at the proper distance from
the bolt heads. Then, check the wiring from the sensor up to the guage. I had a wire break in the wheel well. Finally, check the ground for you guage cluster.

Do all the above, not necessarily in the order I listed.

luvrbus · April 12, 2016, 06:25:50 AM

I use a nickle to check the clearance fwiw

jackhanow · April 12, 2016, 08:26:47 PM

I would do the bolt check. The cruise just counts pulses at the time of engagement and tries to maintain the frequency.