Intermittent field wire (alternator issue)

Dave Defferding mstrblastr at
Wed Jun 7 00:42:26 EDT 2006

It's not clear to me if you are jumping around/past the voltage regulator. 
If you are, I would NOT use a direct connection from the field to the + jump 
post full time.  Here's why.  When the field is energized full time the 
voltage output will continue to increase unimpeded when alternator rpm 
increases-- up to maybe 130V DC or more!!!  This "trick" will not work on an 
alternator with an internal regulator.  The voltage regulator breaks that 
current supply so that voltage is maintained at the "right" level, 
independent of engine speed.  I don't know if our vehicles have external or 
internal voltage regulators.

I once built an add-on pulley and "extra" alternator bracket to run my 
electric chain saw on a Ford Pickup.  I had it geared so that at ~1200 rpm, 
a fast idle, would give me ~120V output  from my 130amp alternator to which 
I wired in a standard duplex outlet to connect to my saw via an extension 
cord.  It worked well as most small electric motors are universal motors and 
will run on AC or DC, with the caveat that they run variable speed, 
proportional to voltage, on DC.  You may already know all of that, but no 
harm in mentioning it.

Good luck of figuring out the problem.

Dave D
'91 200Q
>  _____
> From: Schaible, David
> Sent: Tuesday, June 06, 2006 2:28 PM
> To: 200q20v at
> Subject: Intermittent field wire (alternator issue)
> What exactly does the circuit board in the dash do for the field wire ?
> Has anyone with flaky dash syndrome had alternator issue?  Can the
> intermittent ground in the dash cause this?
> I was able to get the alternator working by hooking up a manually
> switched field wire.  Can you run with a direct link from the field to
> the + jump post full time?
> David Schaible

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