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Cooperative Motor Works

Vintage RV & Motorhome restorations - "The GMC Coop"

You are here: Home / The Daily Pose / GMC Motorhome: 1 wire alternator wiring modification ans a road test……….

October 21, 2019

GMC Motorhome: 1 wire alternator wiring modification ans a road test……….

Already had a big day planned, the big road test for the 72 Revcon project was already planned but equally important first thing I wanted to go over our wiring mod to let the 1 wire alternator service us.  Here it it:

So last month I introduced the things we learned on Deco modifications to our original alternator casing.

The upgraded 130amp diode coach and the slow ramp up of charging current.  These new features added to our original alternators was a needed improvement, thank you Delco.

The 3rd update feature is getting rid of the external trigger circuit Our original alternators needed to do its thing.  The reason this change is important is it does away with the “nichrome trigger circuit” that we all have seen causes fire dangers in our coaches engine electrical system harness.

All of us have added various bandaids to try and lesson our exposure but those were trying to fix the inherent problems no one knew about when trying to charge multiple batteries with our first design alternator.

All that sounds great but there needs to be a rewire to allow this 1 wire, higher output 2nd design alternator for it to do its thing.

Last month I drew up a quick rewiring to accept this 1 wire alternator.  Unfortunately, I should have spent a little more time thinking about this rewire circuit.  I was more interested in the alternator itself not worrying ad much on the circuit.  Under normal driving conditions, we recommend tiring all batteries together for alternator charging……doing that the simple circuit worked fine but it did not isolate the engine battery during living area operation……sorry bout that chief .

I have found over the years there are some on the GMC social network sites there are those self professed gurus seem to take great pride in sitting on their lillypad approving or disapproving things that come up in their Perdue.  I hate that those throw up roadblocks arguing about seemingly every unique idea.   In this case they dissected my idea and what I feel was a rude way to point out the issue.  A tiff insued which was not real pretty.  I do appreciate one guru who approached me with less aggression which helped me understand think A more, thank you for that help.

So when we make this move to improve and make our charging system better and safer, below is how to get these improvements.  Sorry for my sloppy drawing, as you can see ill never be a technical graphic artist!oops, don’t know how to rotate using my phone and I was thinking of drawing it again….I have boxes of that old holed computer paper I scribble on………but no time and well, when you pick up one of the new technology “isolator/combiners” there will be ample instructions.

Yes, I’ve now been forced to throw our beloved blue donned thing (battery isolator) under the proverbial bus for this application.  Its old technology when you COULD isolate the 2 electrical systems by floating the alternator output.  That circuit won’t work completely in this application anymore.  It WILL still isolate a 2 battery pair but not the way it used to so now we move on to “isolator/combined”.  The unit we have selected, there are many out there, is the Samlex brand, ACR-160As I said, there are several brands of these things some more suited than others.  If you can read the specs on my poor sideways drawing, this is not merely a mechanical relay pulling current and creating heat.  When off it only draws 1.8ma which is less than 1/2 of what the memory in your dash radio pulls and when on the electronic switching circuit only pulls 340ma which is @ the memory in the radio so this thing is one that does its job well and completely.

On line you can find these for @ $100.  Yeah….I know…..more money!  Hey but this is new technology, better and safer for our GMC.  What can I say……….

So all you naysayers were……kinda right.   My circuit was not the best circuit and we now need to embrace this new style of charging……..no .8 volt drop……no nichrome trigger circuit to burn up your electrical harness……a stronger 130amp regulator……slower charge at low RPM to help with alternator heat buildup and all in our same original alternator casing.   “Video killers the radio star…..” …say Farwell to our blue donned things and get in here Megatron!

I hope this clears things up with everyone, I’ve asked Kim Weeks to put this update in the next “Vintage RVing” publication to clear it up there and I’m doing a video this week to personally explain all of this real soon.  This is a great update and a real safety issue for our coaches, lets get it right…….

And for the rest of us who have not made the change, have no fear…..I’m keeping my old system until the alternator craps out again…..come to think about it Larry has been charging 16 volts (hard charge) for a while….I should put this on it.   Tell ya what, I’ll do that and do a video……stay tuned.

Ok, I have a drive with some prospective owners and a road test on this critterWITH its new front and maybe back bumper…..there are a couple of issues to iron out on them.

Talk ta ya tomorrow and really, please call me direct at 321.299.5707 if you have any questions…..see ya later.

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Article by jimbounds / The Daily Pose

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