| Generator Light [message #336471] |
Tue, 28 August 2018 19:32  |
Bruce Hart
Messages: 1500
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
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Senior Member |
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Need some advice on why the generator light won't come on when I turn the key switch to on position.
Generator light will come on bright when I start up the engine and stays on.
I checked the voltage at the isolator and was charging at 15.7 volts.
This also happened to a spare alternator I had. Both alternators tested good at NAPA
Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: [GMCnet] Generator Light [message #336474 is a reply to message #336472] |
Tue, 28 August 2018 21:51  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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15.7 volts measured at which terminal of the isolator?
There are two leads going to the terminals of the alternator. One of them goes through alternator light and provides power to start the alternator anytime the key is on. The second terminal is a sense line to the alternator to tell it that the voltage in the coach is correct. I would get out a wiring diagram and start measuring to see if those wires are intact.
When mine went over voltage it was a poor connection on the sense lead where it plugged in to the alternator. I squeezed the terminal with a pair of pliers for a better connection and took care of the problem.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Generator Light [message #336477 is a reply to message #336476] |
Wed, 29 August 2018 06:55 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Bruce Hart wrote on Wed, 29 August 2018 06:15Emory, it happened with both alternators.
Will check the fuse next,
Ken, checked voltage at center post of isolator. Will follow up with
connector.
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
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OK, so you are about 1 volt over expected. That point should be around 14.7 volts give or take a few 1/10s of a volt. The other two terminals on the isolator should be around 14.0 volts again give or take a few 1/10s.
This is from memory and could be wrong. Thee is a sense lead that is connected to the big terminal on the horn relay. On that same terminal is the fusible link connected to the isolator. The wire you want is a #12 red one that goes to the alternator pin #2. Along it's route it changes colors from red to white. I would be reading the voltage at the horn relay and also at the #2 terminal at the alternator. They should be the same reading and around 14.0 volts with the engine running.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Generator Light [message #336485 is a reply to message #336477] |
Wed, 29 August 2018 09:56 |
JerryW
Messages: 256
Registered: August 2018
Karma: 1
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Senior Member |
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Are you using the Gene Fisher UPC cable attached to the alternator?
Emery Stora
> On Aug 29, 2018, at 5:55 AM, Ken Burton wrote:
>
> Bruce Hart wrote on Wed, 29 August 2018 06:15
>> Emory, it happened with both alternators.
>> Will check the fuse next,
>> Ken, checked voltage at center post of isolator. Will follow up with
>> connector.
>>
>> Bruce Hart
>> 1976 Palm Beach
>> Milliken, Co
>> GMC=Got More Class
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> OK, so you are about 1 volt over expected. That point should be around 14.7 volts give or take a few 1/10s of a volt. The other two terminals on
> the isolator should be around 14.0 volts again give or take a few 1/10s.
>
> This is from memory and could be wrong. Thee is a sense lead that is connected to the big terminal on the horn relay. On that same terminal is the
> fusible link connected to the isolator. The wire you want is a #12 red one that goes to the alternator pin #2. Along it's route it changes colors
> from red to white. I would be reading the voltage at the horn relay and also at the #2 terminal at the alternator. They should be the same reading
> and around 14.0 volts with the engine running.
>
>
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] Generator Light [message #336486 is a reply to message #336472] |
Wed, 29 August 2018 09:58 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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Read here
http://www.gmcmhphotos.com/photos/data/15/GMC_charging_system_checkout.pdf
On Wed, Aug 29, 2018 at 7:57 AM Emery Stora via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Are you using the Gene Fisher UPC cable attached to the alternator?
>
> Emery Stora
>
>> On Aug 29, 2018, at 5:55 AM, Ken Burton wrote:
>>
>> Bruce Hart wrote on Wed, 29 August 2018 06:15
>>> Emory, it happened with both alternators.
>>> Will check the fuse next,
>>> Ken, checked voltage at center post of isolator. Will follow up with
>>> connector.
>>>
>>> Bruce Hart
>>> 1976 Palm Beach
>>> Milliken, Co
>>> GMC=Got More Class
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>> OK, so you are about 1 volt over expected. That point should be around
> 14.7 volts give or take a few 1/10s of a volt. The other two terminals on
>> the isolator should be around 14.0 volts again give or take a few
> 1/10s.
>>
>> This is from memory and could be wrong. Thee is a sense lead that is
> connected to the big terminal on the horn relay. On that same terminal is
> the
>> fusible link connected to the isolator. The wire you want is a #12 red
> one that goes to the alternator pin #2. Along it's route it changes colors
>> from red to white. I would be reading the voltage at the horn relay and
> also at the #2 terminal at the alternator. They should be the same reading
>> and around 14.0 volts with the engine running.
>>
>>
>> --
>> Ken Burton - N9KB
>> 76 Palm Beach
>> Hebron, Indiana
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
> _______________________________________________
> 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://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] Generator Light [message #336518 is a reply to message #336486] |
Wed, 29 August 2018 20:03 |
Bruce Hart
Messages: 1500
Registered: October 2011
Location: La Grange, Wyoming
Karma: 5
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Senior Member |
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Checked the connector and all seemed good, removed small fuse and checked
ohm value, That was ok.
Found fuse for gauges was bad and now generator light functions correctly.
Thanks all for the help
Emery, recently received APC from Eugene Fisher and installed. (Did not
correct issue).
On Wed, Aug 29, 2018 at 8:59 AM gene Fisher wrote:
> Read here
> http://www.gmcmhphotos.com/photos/data/15/GMC_charging_system_checkout.pdf
>
>
>
> On Wed, Aug 29, 2018 at 7:57 AM Emery Stora via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> Are you using the Gene Fisher UPC cable attached to the alternator?
>>
>> Emery Stora
>>
>>> On Aug 29, 2018, at 5:55 AM, Ken Burton wrote:
>>>
>>> Bruce Hart wrote on Wed, 29 August 2018 06:15
>>>> Emory, it happened with both alternators.
>>>> Will check the fuse next,
>>>> Ken, checked voltage at center post of isolator. Will follow up with
>>>> connector.
>>>>
>>>> Bruce Hart
>>>> 1976 Palm Beach
>>>> Milliken, Co
>>>> GMC=Got More Class
>>>> _______________________________________________
>>>> GMCnet mailing list
>>>> Unsubscribe or Change List Options:
>>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>>
>>> OK, so you are about 1 volt over expected. That point should be around
>> 14.7 volts give or take a few 1/10s of a volt. The other two
> terminals on
>>> the isolator should be around 14.0 volts again give or take a few
>> 1/10s.
>>>
>>> This is from memory and could be wrong. Thee is a sense lead that is
>> connected to the big terminal on the horn relay. On that same terminal
> is
>> the
>>> fusible link connected to the isolator. The wire you want is a #12
> red
>> one that goes to the alternator pin #2. Along it's route it changes
> colors
>>> from red to white. I would be reading the voltage at the horn relay
> and
>> also at the #2 terminal at the alternator. They should be the same
> reading
>>> and around 14.0 volts with the engine running.
>>>
>>>
>>> --
>>> Ken Burton - N9KB
>>> 76 Palm Beach
>>> Hebron, Indiana
>>>
>>> _______________________________________________
>>> GMCnet mailing list
>>> Unsubscribe or Change List Options:
>>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
>> _______________________________________________
>> 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://gmcmotorhome.info/
> Alternator Protection Cable
> http://gmcmotorhome.info/APC.html
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Bruce Hart
1976 Palm Beach
Milliken, Co
GMC=Got More Class
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
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Bruce Hart
1976 Palm Beach
1977 28' Kingsley
La Grange, Wyoming
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| Re: [GMCnet] Generator Light [message #336519 is a reply to message #336518] |
Wed, 29 August 2018 20:35 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I am still worried about the high voltage at the isolator (all three terminals). Please check the voltages again.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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