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VDO Analogue Tachometer and Speedometer on our 1997 U320

November 02, 2013, 04:07:55 pm

We are having trouble with our VDO Analogue Tachometer and Speedometer.  When stationary the tachometer seems to work.  Going down the road at 65 MPH the speedometer says we are going 32 MPH @ 700 RPM's.  Just stopped at a truck stop and wiggled all the connections under the dash with no improvement.  All other gauges appear to be functioning properly. Anybody have any thoughts?

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Re: VDO Analogue Tachometer and Speedometer on our 1997 U320

Reply #1 – November 02, 2013, 05:05:40 pm

Hi John;

I just replaced my tach about 3 weeks ago on my 1998 U270. I believe they are the same.

At first when I put it into the dash it did not work, said a few nice ones. Called FT talked with, gee can't remember his name, he is tech assist. He said there are codes that must be entered to make it work, hmmmmm.

My tach had not worked since I had a new Alt. put in last spring. Not sure here but a here's a guess, have you lost the 12v to the panel at some time, which may have caused the code to be erased. I'm sure there is someone out there that can give you a more positive answer. At any rate you can get the code by giving him, FT Tech Assist, by giving him your build number. He also has a pdf file with instructions.

The other part in question may be the sending units on the engine. Not likely both sending units would go at the same time. The tach was $140, don't know about the speedo, sending unit for the tach was $37 of course plus shipping. Did not need the sending unit.

Hope this helps. Just thought I would give my experience.

Norm

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Re: VDO Analogue Tachometer and Speedometer on our 1997 U320

Reply #2 – November 02, 2013, 05:40:42 pm

There is an Android smart-phone (and tablet) app called "Ulysse Speedometer" that makes a great addition to your RV tool kit with a big easy-to-read speed indicator in digital form as well as an analog representation. Also shows time, trip distance, elevation, battery use, and compass heading.

Best of all, it has a HUD (Heads Up Display) mode so you can lay it on its back on the dashboard show it looks up at the windshield and it projects a reverse image of speed (only) onto the windshield so you don't have to look down. Visible night and day except in bright sun right on the windshield.

I use mine all the time. Hardly ever notice the speedometer any more.

Craig

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Re: VDO Analogue Tachometer and Speedometer on our 1997 U320

Reply #3 – November 02, 2013, 06:07:21 pm

John,

I pulled out the wiring diagram on a 1993 U240.  Suspect the instruments are similar.

Both tack and spedo share a 12 VDC positive, so that is where I would start.  Verify you do, indeed have 12+ VDC to each.

The spedo shares ground with a number of other gauges.  Be sure the ground is tight.  If in question, add a separate ground.

Brett

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Re: VDO Analogue Tachometer and Speedometer on our 1997 U320

Reply #4 – November 02, 2013, 09:44:41 pm

Thanks wa_desert_rat.  We were able to download a free iPhone app that has a very nice large digital reading....we made good use of it all afternoon.

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Re: VDO Analogue Tachometer and Speedometer on our 1997 U320

Reply #5 – November 02, 2013, 10:01:21 pm

Nice new coach you are showing there today.  We all hope the drive home is a fun time that is just the start of more in the future.

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Re: VDO Analogue Tachometer and Speedometer on our 1997 U320

Reply #6 – December 02, 2013, 08:48:56 pm

95' 320 w/erad tach signal (me too). 
So far.  Replaced engine position sensor (same erad signal). 
Next, confirmed the ECM, which indicated no issues. 
Next, checked resistance (it was smooth) to tach, same erad tach.

I thought something was amiss within (diode?). 
Yep, seems the VDO website has a directive for this issue (add a diode). 
No, you do not have to open the tach, just add the diode.
Stay tuned.. pc

Ps. I'm at 50/50 on this for results. 
But, it is a bunch cheaper if it will fix the issue.

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