T&T: Tachometer Problem

[Scott H.E. Welch]

GARY RITZMAN <ritzmans at msn.com> writes:
>One of the VDO tachs for my Lehman 135s seems to "skip" or "bounce." For
>example, running at 1700 RPM, it will drop to zero and then immediately
>bounce
>back up to 2000 before settling back to 1700. I thought that perhaps the belt
>was loose but that does not appear to be the problem. Any suggestions from
>the
>fertile minds of this knowledgeable  group?

Well, I have good and bad news.

The good news is that I know what causes this, because it also happens to me
on my VDO tach. It happens when the batteries reach full charge and the field
current on the alternator drops to such a low point that the tachometer feed
from the alternator is too weak for the tach to read.

The bad news is that I have not yet figured out what I can do about it, other
than installing a dedicated tachometer sender.

Perhaps someone else has a suggestion?

Scott Welch
FirstClass Product Manager
www.firstclass.com

Those who make no mistakes rarely make anything.