Upgrading the big 3 or big 4 wires?

[6cuda6]

Has anyone taken the time to upgrade all 3 or 4 charge wires for the engine side? (So alt poss to bat...alt neg to bat or block....neg bat to
frame....neg frame to engine...i know we have an isolator in there but you get the picture). Did you see an improvement in charging?
--
Rich Mondor,

Brockville, ON

77 Hughes 2600

 

[Jim Hupy]

Probably a good idea to do the math. GM sized the alternator harness to
work ORIGINALLY with the 66 amp alternator. At least ONE upgrade was done
when HEI was introduced in mid year 1976. The resistance wire was no longer
needed for the ignition primary, and the Alternator output was changed to
80 amps.
Somewhere in there, there was a dealer notification (not a recall)
about that fire starter resistance wire bundled into the harness under the
dash. When it got hot enough to fail, it melted all the conductors included
with it in the harness. Bad ju-ju.
Bring that up to today, and many of us have further upgraded the
charging system with 100 amp alternators with double belts and larger
conductors to the CENTER POST of the Isolator. That is where the alternator
output goes to, first. Then it exits the isolator via the top and bottom
posts. Figure your ampaciity from those points. If yours pencils out to
have a 40 - 50% overkill, then leave it be. If you have less than that,
then upsize everything downstream from those posts to the batteries. That
might include things like relays and shunts as well. These coaches have all
been tampered with in there. Check all the crimped connectors for sure, and
fix what needs it. Some don't need much, and others, O.M.G. what a mess.
Jim Hupy
Salem, Oregon

On Thu, Nov 14, 2019, 6:36 AM tonka6cuda6--- via Gmclist <

> Has anyone taken the time to upgrade all 3 or 4 charge wires for the
> engine side? (So alt poss to bat...alt neg to bat or block....neg bat to
> frame....neg frame to engine...i know we have an isolator in there but you
> get the picture). Did you see an improvement in charging?
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[gmcnet1]

> Has anyone taken the time to upgrade all 3 or 4 charge wires for the engine side? (So alt poss to bat...alt neg to bat or block....neg bat to
> frame....neg frame to engine...i know we have an isolator in there but you get the picture). Did you see an improvement in charging?

What sort of problem are you having with charging? If you connect a meter to your battery terminals (or even just read your voltage gauge as a
starting point), what does it read with the engine running?
--
Christo Darsch
GMC Nor'easters
1977 Eleganza II - "The Komet"
3.50 Power Drive, Disc Brakes, Alcoas
Weymouth, MA

 

[Rdenney]

I have done so, but I eliminated the isolator and installed a combiner in
its place.

I can’t say I’ve needed to monitor the charging from the alternator closely
enough to notice any improvement.

I suspect my primary wire from the alternator to the master power terminal
could be bigger, but I don’t worry much. Alternator output ratings are
peak, and require optimal temperatures and RPMs to attain a large fraction
thereof.

Jim is right that it could be sized by downstream demands. Lead-acid
batteries can only take about 25 amps charging, as I recall, so two
depleted batteries will draw 50 amps. The air pump might draw 10 amps, and
a supplemental vacuum pump the same. Headlights are less. Ignition is much
less, even with HEI. Even with a “larger” alternator, I doubt we really
overload the stock wire from the alternator.

Corroded connectors? That’s a whole other thing. And wiring a battery
backwards? Not good; ask me how I know.

I’d bet that *most* cases of poor charging or starting current are related
to bad ground straps. I’ve replaced all those, too, and it’s probably about
time to do it again. I ran a large-diameter wire (maybe #2, but I don’t
recall) from the battery to a bolt on the engine block, and from there to a
chassis bolt.

Rick “about time to go battery shopping anyway” Denney

On Thu, Nov 14, 2019 at 9:36 AM tonka6cuda6--- via Gmclist <

> Has anyone taken the time to upgrade all 3 or 4 charge wires for the
> engine side? (So alt poss to bat...alt neg to bat or block....neg bat to
> frame....neg frame to engine...i know we have an isolator in there but you
> get the picture). Did you see an improvement in charging?
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com

 

[6cuda6]

I actually dont have a charging problem...i was just curious as bigger wires usually means less resistance therefore less voltage drop etc.....

The only problem i do have, which is really unrelated is a "gen" light that momentarily flickers on then off when the blower fan is put on
high.....hence my other thread about ditching the Nichrome wire.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600

 

[mghamms]

I change to larger wires when I upgrade and just assume the ones or there are good if no apparent problems.
--
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts

 

[john r. lebetski]

Voltage drop on the alternator main wire to isolator is a mute point. The sense cable to regulator is after the isolator and so all voltage drop
before that gets made up for. I don't know why you would remove the isolator to add a combiner when you can simply add the combiner to the factory
setup. Also In the event of an internal alternator short while parked the isolator eliminates a fire hazard.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[john r. lebetski]

Also if you arr worried about thin wires, the ones you are worried about are not the bottleneck. The fusible link is way smaller gauge. And you don't
want to change that gauge.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[Jim Hupy]

Know the maximum possible load on the conductors, and size your wires
accordingly. Tain't rocket science, just ohms law.
Jim Hupy
Salem, Oregon

On Thu, Nov 14, 2019, 6:29 PM John R. Lebetski via Gmclist <

> Also if you arr worried about thin wires, the ones you are worried about
> are not the bottleneck. The fusible link is way smaller gauge. And you don't
> want to change that gauge.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

 

[steve southworth]

> I
>
> I'd bet that *most* cases of poor charging or starting current are related
> to bad ground straps. I've replaced all those, too, and it's probably about
> time to do it again. I ran a large-diameter wire (maybe #2, but I don't
> recall) from the battery to a bolt on the engine block, and from there to a
> chassis bolt.
>
> Rick "about time to go battery shopping anyway" Denney

If you have not inspected your 3 primary ground straps check these pictures:

http://www.gmcmhphotos.com/photos/g6081-frame-ground-connections-2c-1974.html

If these straps fail the current may flow in other connections between body, frame or engine. What kinds of other connections? Brake lines, throttle
cables, transmission shift cables and who knows what else. Hopefully larger bolts will be the alternate path.
--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI

 

[Ken B]

> Has anyone taken the time to upgrade all 3 or 4 charge wires for the engine side? (So alt poss to bat...alt neg to bat or block....neg bat to
> frame....neg frame to engine...i know we have an isolator in there but you get the picture). Did you see an improvement in charging?

Well let's see. On the engine side the master ground for everything is the engine block and because they are bolted to the engine also the
transmission and final drive can be considered the master ground.

1. Alt positive to bat
The real question on this one is how much current are you expecting to run across this path. I suggest that this path might briefly max out at 40
amps but quicky will drop to around 25 and slowly drop from there as it charges. There are other possible current flows in parts of this path
(lights, blower, etc. The highest current part of the path would be between the isolator and the alternator. You might consider making this heavier
than the OEM 10 ga but you will not see any increased voltage at the battery because the alternator monitors the voltage farther down this path and
raises the voltage if it is low.

2. Alternator neg to battery or block
There is no cable between the alternator and the block. The alternator is mounted directly to the master ground (the block). The rest of the path to
the battery path is the negative battery cable which is connected directly to the engine block (master ground). If the cable works OK during starting
(a couple hundred amps), then it is fine for a charging current of 25 or so amps.

3. Negative (engine) battery to frame
This path does not exist. There should never be any battery charging or discharging current coming from the frame to the battery.

4. Negative frame to alternator
This path exists only for charging the house batteries from the alternator and when using the battery boost switch. It is braided jumpers between
the back of the transmission and the frame plus two more braided jumpers from the frame to the body. They are located across the right front body
mount and in the left rear if you have an Onan installed. The normal charging current would be 0 to 40 amps on this path depending on the batteries
installed and their state of charge.
I suggest that your efforts would be more efficiently spent inspecting these three jumpers and then disconnecting and cleaning the connections.
Reinstall the connections with anti-oxidation grease available from Home Depot.
You could replace them but I do not see any benefit in doing this.





1
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana