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VDO Tachometer Troubleshooting?

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K4ZDZ

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Oct 29, 1996, 3:00:00 AM10/29/96
to

I have a VDO Tachometer on my boat and am seeking info on how to
troubleshoot it. The Tach has 4 connectors at its head, a 12V+, a 12V-,
and two leads from a mechanical sending unit on a Volvo diesel engine.

Since the Tach stopped reading anything, I need to determine whether the
sending unit or the indicator is bad. I'd hate to buy the wrong one!

I would presume (dangerous thing to do) that the 2 leads from the sending
unit merely send a "pulsed" signal as a result of making/breaking contact,
is this the case?

Any Marine Electronic Techs out there??

Sam Goldwasser

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Oct 30, 1996, 3:00:00 AM10/30/96
to

It could be a switch or a magnetic or capacitive sensor. It is probably safe
to try shorting those contacst together and seeing if it will register. This
would work if it is a switch. Touching a 1.5 V cell through a capacitor
to the inputs may trigger it if it is an inductive or capacitive pickup.

I don't suppose getting to the sending unit is a joy, huh? If you can,
then you could probably do some tests on it.

--- sam

Sandy Morton

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Oct 31, 1996, 3:00:00 AM10/31/96
to

> I have a VDO Tachometer on my boat and am seeking info on how to
> troubleshoot it. The Tach has 4 connectors at its head, a 12V+, a 12V-,
> and two leads from a mechanical sending unit on a Volvo diesel engine.

Don't know about Volvo in USA but Volvo in GB have always been extremely
helpful.

Any Tachs which I have seen which had four wires were connected as
follows:-
12v+, Ground, Signal (normally from the alternator) and panel lighting.

Hope this helps.


sandymillport
on the bicycle island
GM8BJJ

k4...@aol.com

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Nov 1, 1996, 3:00:00 AM11/1/96
to

Thanks, since it is such a chore to get to the sending unit, I am writing
to VDO and VOLVO for advice.

Jeff Roberts

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Nov 2, 1996, 3:00:00 AM11/2/96
to

I can give you VDO's address and phone number
They should know

VDO Yazaki Corporation
980 Brooke Road P.O. box 2897
Winchester, Virginia 22601
703-665-0100

VDO Yazaki Corporation
455 Welham Rd. Box 8700
Barrie, Ontario L4V-1L2
705-722-6400


k4...@aol.com (K4ZDZ) wrote:

>I have a VDO Tachometer on my boat and am seeking info on how to
>troubleshoot it. The Tach has 4 connectors at its head, a 12V+, a 12V-,
>and two leads from a mechanical sending unit on a Volvo diesel engine.

>Since the Tach stopped reading anything, I need to determine whether the


>sending unit or the indicator is bad. I'd hate to buy the wrong one!

>I would presume (dangerous thing to do) that the 2 leads from the sending
>unit merely send a "pulsed" signal as a result of making/breaking contact,
>is this the case?

>Any Marine Electronic Techs out there??

Jeff Roberts

http://bcyellowpages.com/advert/j/j.r.electronics.html
jrob...@axionet.com


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