Q: Alternator Ground Path

[240260280z]

I saw an electrical strap in parallel with an add-on alternator adjuster. The purpose was to ensure the electrical return path to the alternator was maintained.

 

This made me wonder first about galvanic corrosion of the timing cover bolts (as they are probably the current path from the block to the alternator as the timing cover is insulated by the gasket. 

 

But... after more thought, the alternator is also bolted at the bottom to the block.

 

I am guessing that adding a copper strap from the battery ground at the transmission/starter area directly to the alternator would be a useful modification to reduce electrical currents in the block.

 

Anyone have more insight on this?

 

[Mark Maras]

 I have been curious about the source of the pitting inside the t. cover for a while & your theory about the current path (or lack of it) thru the block may explain why. Some old covers are pitted & others not. Is it possible that without a "solid" ground thru any of the bolts & assuming that the coolant is acidic enough to act as an electrolyte, is it likely some of the current is flowing between the dissimilar metals, pitting the alum? It may also be the pitting is caused by galvanic action alone. Any thoughts?

[240260280z]

I just found a diesel mfgr's report on a similar path and the damage it causes including pitting.  I bet you are right in your observation.

[240260280z]

Read the field problem observations: http://www.dieselduck.info/machine/01%20prime%20movers/coolant_voltage.htm

[240260280z]

I wonder if the rot that sometimes happens on the aluminium fittings for the radiator is also related?

[Zed Head]

Don't know about the other years but my 76 has a ground wire from the harness for the alternator.  To the E post. It's branched to several others on the the way to where ever it's attached.  Considering the years, maybe corrosion affects its ability to function also.  An added wire from post E to the engine block might be good insurance.

[grannyknot]

An old mechanic told me once that I should always add a heavy gauge ground strap from the alternator to the frame of the car and another from the engine block to frame.

Hopefully I've averted possible problems.

 

[Patcon]

Grannyknot,

I think you need bigger cables!  Just kidding. I love the wiring in your engine bay. Bigger cables are good...

[Mark Maras]

 Thanks for the tech article. The testing procedure is particularly interesting.

 I remember the elec. gremlins that arose from not replacing the ground wire on the valve cover of the small block Chevys. My dad always said "you can't have too many grounds" & proved it many times by bringing a circuit to life by adding a ground. Easier than finding the bad connection for him.

 Coolant as a ground circuit=corroded rad. fittings, timing covers, diesel engine blocks maybe even Subaru head gaskets. I think I'm going to run the tests on my Subie first.