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Re: [T3] GEN light on AGAIN!

On 21 Nov 2003 at 12:22, Mike Wodkowski wrote:

> > Turn the engine off.
> > 
> > Remove all the wires from the D+ and DF terminals on your new generator and
> > push those wires out of the way. Make the following resistance measurements:
> > 
> > What is the resistance between D+ and ground on the generator?
> Zero

It's actually slightly above zero, but still less than 1 Ohm, so this sounds 

> > What is the resistance between D+ and DF on the generator?
> Infinity

This should be 3-4 Ohms. The field windings of the generator are connected 
directly between these 2 terminals, and their wires should be soldered directly 
to the underside of the terminals. If your field winding is open the generator 
will never generate. Sound familiar?

Double-check this (use the R x 1 scale on your VOM), and if it still stays 
high, return it for a better one. This was a rebuilt, I assume; who rebuilt it?

You could try looking inside the generator to see if you see any signs that a 
wire has come loose, broken, burned thru or that a field winding is charred 
from overheating. You can see the field windings from the brush holes and from 
the air hole. I'm concerned that your string of problems all have a common 
cause which we haven't fixed yet. One thing that might explain all of these 
problems would be  that the DF wire has an occasional short to ground somewhere 
between the DF terminal on the generator and the DF terminal on the VR. If this 
happened, it would turn the generator on full blast (this is called "full 
fielding" the generator, often done for testing) and would burn out the field 
windings if driven this way for a few minutes. The generator light would 
probably be on during this process.

You had a second wire connected to one of the generator terminals at one time. 
I believe you measured that as being grounded at one time, although it cleared 
up without explaination. You should be just running this generator with one 
wire on each terminal (D+ and DF) but there is a separate brown wire that runs 
to a ground screw on the generator body. If you count that wire, that's 3 wires 
total to three connection points.  

You should check where the wire disappears into the wiring harness, and where 
the wiring harness goes into the bodywork. Then check the other end at the VR. 
One possibility at the VR end would be that the seat belt buckle had fallen 
against the VR and shorted the DF terminal to ground. You should also inspect   
the DF wire for scrapes and breaks in the insulation at that end.  

Jim Adney
Madison, WI 53711-3054

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