<VV> more grounds?

[Larry Forman]

At 08:00 PM 1/4/2005 -0800, Jim Briggs wrote:
>Ok wise ones.  Recently my tach quit working intermittently. After a 
>while, I realized it quit only when I was in reverse (4spd) or when I turn 
>on the heater fan. I figure its a ground problem but where do you all 
>suggest I start to look?
>
>Jim Briggs
>3 LM's

Hi Jim,
OK, so you have a Late.  That means the poor dash ground could be causing 
you problems.  There is only one relatively poor ground to the grounding 
flexible strip.  I like to take some heavier gage insulated wire, like 16 
or larger, and make a grounding wire attached to the grounding strip inside 
the dash and then with a couple of feet wire ground to the screw holding 
the flasher under the dash.  That is a good grounding location and whether 
or not the bottom dash grounding screw is there you always have a good ground.

One possible reason that the ground, or rather lack of ground, can cause 
problems, is that when current flows for certain accessories it can create 
a voltage drop and other electronics will then stop working.  Since the 
heater fan takes several amps, it can easily create a voltage drop of a 
couple of volts to stop something like a tach.  Look for other loose or 
defective grounds.

An approach to "snooping" for faulty grounds is to take a LONG insulated 
heavy gauge wire clipped directly to the battery and then ground various 
items and see if the defective item suddenly starts working.  Then add a 
ground right there and keep looking if needed.

-- Larry