Alternator

Russell

Russell

Active member
Jan 2, 2017
357
88
28
Dunedin, Florida
When we bought our '78 GMC Eleganza II this past August, it came with decent maintenance and repair records back to 1983. I was digging through the
documentation again last night to see when the alternator was last replaced, and could not find any record of a new alternator. According to the
voltmeter in the dash, the alternator is putting out about 13.5 volts under load with the lights on. Could this actually be the original alternator?
(see pics below) I could not find a part number or model number on the current alternator. If it is original, does someone have a current part number
and recommended brand for a replacement? I think the alternator is charging the house batteries as well as the chassis battery. Do I need to go with
the 100 amp alternator, or an 80 amp?

Thanks again for the help.
Russell

http://www.gmcmhphotos.com/photos/data/7016/medium/alternator2.jpg

http://www.gmcmhphotos.com/photos/data/7016/medium/Alternator_Back.jpg

http://www.gmcmhphotos.com/photos/data/7016/medium/20170114_144002.jpg
--
Russell Keith

1978 Eleganza II

Dunedin, Florida
 
Could be original. But Delco is a decent one either way.

I am not positive you are diagnosing that as bad, putting out 13.5 volts, but others or you can figure out if that is enough, and what the voltage is
doing with engine off/ vs running.

my advice is to pull that Delco out, and bring it to a "rebuilder". it is a good unit, and they can fix it cheap and usually do a good job. Any
replacement off the shelf alternator is ify as to how good of a new unit it is.

a quick google search, I would bring it to: ADVANCE ALTERNATOR AND STARTER SVC.  
4.925 Google reviews
Auto Electrical Service
Address: 1982 Sherwood St, Clearwater, FL 33765
Phone: (727) 442-6344


--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/
 
Thanks Jon. Good Advice. Those guys are 10 minutes from my house, and the reviews look pretty good.
--
Russell Keith

1978 Eleganza II

Dunedin, Florida
 
Looks to me like a later style fan. Bearings and brushes ( wear items ) are easily replaced. You should check voltage under a variety of conditions,
as it varies with temp to try to match battery charging requirements. Should be up near 14.2 after cold start then taper down as underhood temps rise
to about 13.4V
--
John Lebetski
Woodstock, IL
77 Eleganza II
Source America First
 
It's done and continues to do what it's supposed to for at least 33 years.
Don't fix it if it isn't broke. That's when you'll start having trouble.

When we bought our '78 GMC Eleganza II this past August, it came with
decent maintenance and repair records back to 1983. I was digging through
the
documentation again last night to see when the alternator was last
replaced, and could not find any record of a new alternator. According to
the
voltmeter in the dash, the alternator is putting out about 13.5 volts under
load with the lights on. Could this actually be the original alternator?
(see pics below) I could not find a part number or model number on the
current alternator. If it is original, does someone have a current part
number
and recommended brand for a replacement? I think the alternator is charging
the house batteries as well as the chassis battery. Do I need to go with
the 100 amp alternator, or an 80 amp?

Thanks again for the help.
Russell

http://www.gmcmhphotos.com/photos/data/7016/medium/alternator2.jpg

http://www.gmcmhphotos.com/photos/data/7016/medium/Alternator_Back.jpg

http://www.gmcmhphotos.com/photos/data/7016/medium/20170114_144002.jpg
--
Russell Keith

1978 Eleganza II

Dunedin, Florida

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> When we bought our '78 GMC Eleganza II this past August, it came with decent maintenance and repair records back to 1983. I was digging through
> the documentation again last night to see when the alternator was last replaced, and could not find any record of a new alternator. According to
> the voltmeter in the dash, the alternator is putting out about 13.5 volts under load with the lights on. Could this actually be the original
> alternator? (see pics below) I could not find a part number or model number on the current alternator. If it is original, does someone have a
> current part number and recommended brand for a replacement? I think the alternator is charging the house batteries as well as the chassis battery.
> Do I need to go with the 100 amp alternator, or an 80 amp?
>
> Thanks again for the help.
> Russell

Russel,

You are obviously not stupid, but you don't seem to have looked at the whole picture. 13.5V out of the alternator is just fine, under many
circumstances, but you gave us no hint as to the conditions. Obviously the engine is running, but how long since cranking and how much did the
voltage rise as soon as the engine was at idle speed. All this stuff matters. Right now, I'm with those that say leave it alone.

Easy test for any automotive charging systems:
Log the rest terminal voltage. This should be close to 12.5.
When you crank, the terminal should not drop below 10.5. If it does, you have a battery problem.
As soon as the engine is at a stable idle, the terminal should have gone up "about a volt".
Turn one the headlights and the heater blower on. The the terminal stay up? Good the regulator is good.
What happens after that is very situation dependent.

So, unless you have nothing better to do, LEAVE it ALONE.

You don't know me (something many might be thankful for), but I know this stuff.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Still Loving OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Read here

http://gmc49ers.blogspot.com/2014/03/check-your-battery-system-through-your.html

> Thanks guys.
> --
> Russell Keith
>
> 1978 Eleganza II
>
> Dunedin, Florida
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://bdub.net/gmcmotorhome.info/
Alternator Protection Cable
http://bdub.net/gmcmotorhome.info/APC.html
 
The question is where is the voltmeter on the the dash is connected. It probably is connected past the ignition switch. If so then a reading there
of 13.5 with the headlights is perfectly normal. There is several 1/10ths of a volts loss when reading there due to losses in the fusible link,
wiring, and ignition switch. Also where is the ground sie of the meter connected?

If you want to read actual voltages, use the 3 terminals on the isolator and the aluminum plate the isolator is mounted on for ground when you are
teading voltages.

13.5v under load is perfectly normal where you are testing. There is nothing wrong with that alternator.

If the voltage were low under load at the isolator, the first thing I would look for is a slipping / worn fan belt.

If it ain't broke, don't fix it.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
The statement has been made "if it ain't broke, don't fix it.". This is really good advice.

Just take note, If it ain't broke, fix it 'till it is" is also very valid advice.
--
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
 
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