| Hmn power drain? [message #70805] |
Thu, 14 January 2010 12:21  |
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gmcdude76
Messages: 102
Registered: December 2009
Location: Northern Ca
Karma: 1
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Hey,
I have come to think that due to the article bullitin from gmc
that any pre 76 Birchavens have a flaw with the generator light staying on.its only been a day since i changed out my isolator but
i was actually able to turn over my generator.the guage on the panel for battery life is much stronger than normal.the light on the dash is way brighter.
not to say there isent a drain.but perhaps i can maintain my current house batterys without replacing them.the other options is to check the fuse on the dash or install a apc cable on the generator.just some simple(cheap)ways to get around it.i also am not sure if i have a buz box.there is a system
under the sink but its on the floor but am not aware of its function?
Thanks
Gmc76Birchaven 23'94947
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| Re: Hmn power drain? [message #70817 is a reply to message #70805] |
Thu, 14 January 2010 15:38  |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
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Senior Member |
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If the box under the sink is about the size and shape of a shoe box, and it has a 110 lead going into it and three wires coming out of it, or a junction block, it is your buzz box. It's job is to destroy your house batteries by boiling the water out of them.  It should hum or buzz when you are plugged into shore power or running the generator. These are very old technology battery chargers. They work well, but have no internal circuitry to control the current being sent to the battery. Once the battery is fully charged, they just keep on agoin'.
Most people have changed over to a more modern 3-stage battery charger. There are several suppliers, and you can sometimes get a rebuilt one if money is an object. See Progressive Dynamics for an idea.
Do not throw you buzz box away. They make very good bench 12v power supplies, as long as you watch them.
Tom Phipps,
75 GMC Ex-Avion
2012 Phoenix Cruiser model 2552
KA4CSG
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| Re: Hmn power drain? [message #70830 is a reply to message #70805] |
Thu, 14 January 2010 20:11 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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Someone is confused here... it could be me.
1. What bulletin are you talking about? I think there was one for the early coaches for the ALTERNATOR light. It doesn't have anything to do with the "Buzz Box." There are two 12vdc systems in almost all coaches. They should only be connected at the isolator. (And/or combiner if you have one of them.)
2. The Buzz Box is the Power Converter (120vac to 12vdc) for the HOUSE system. Notice I called it a Power Converter NOT a battery charger. While it will charge a battery, it will also OVER charge it.... drying out cells. But only the house battery, as set up from the factory. On a rear bath Birchaven (most of them) the buzz box is under the REFRIGERATOR, right next to the fuse box. (The box under the sink is a vacuum cleaner.) I do not know where these parts are in the side bath Birch, but is suspect it isn't much different.
3. From the factory, there isn't any light for the Onan generator on the dash. I have seen some added.... The Onan Generator light SHOULD be lit anytime the Onan is running.
| gmcdude76 wrote on Thu, 14 January 2010 10:21 |
I have come to think that due to the article bullitin from gmc
that any pre 76 Birchavens have a flaw with the generator light staying on.its only been a day since i changed out my isolator but i was actually able to turn over my generator.the guage on the panel for battery life is much stronger than normal.the light on the dash is way brighter.
not to say there isent a drain.but perhaps i can maintain my current house batterys without replacing them.the other options is to check the fuse on the dash or install a apc cable on the generator.just some simple(cheap)ways to get around it.i also am not sure if i have a buz box.there is a system under the sink but its on the floor but am not aware of its function?
Thanks
http://donsgmcdudes76photos.shutterfly.com/ Gmc76 Birchaven transmode 260/Carson Toyhauler/Burgman 400
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OBTW: A "transmode 260" is 26 foot long. All Birches are 23 foot and where built from 23 foot transmode (230) bodies. I am pretty sure the first Birches where 1976's.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: Hmn power drain? [message #70843 is a reply to message #70805] |
Thu, 14 January 2010 22:25 |
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gmcdude76
Messages: 102
Registered: December 2009
Location: Northern Ca
Karma: 1
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Senior Member |
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Ok i will clarify the situation.
First its a 23 foot Birchaven with side bath.its a transmode version least it says that in the owners manual.i may have thought it was the 260 my bad.also i looked today with a friend and there isent a buz box under the sink?the only thing that is under my sink is part of the furnice line.
The fuse box and electrical stuff is under the closet on the passenger side.the only thing that (rattles)when running i assumed was the pump for the airbag system.its located to the rear behind the bath on the floor.its makes some noise and other gmc owners have told me theres does the same thing.(not sure if if its a BUZZ BOX)?
I was also mixing up the generator light with the alternator light on the dash i guess.it would stay on while the engine is running very dim.when i replaced the (isolater) the light on the dash is much brighter.and the battery guage for the house batterys seems to be more up on the green area.but i still have to fire up the engine to get the house batterys live enough to crank over my generator.
Ill post the link Mr Erfisher posted in my previous thread.one thing now comes into play if i dont have a buzzbox then (what do i have)i guess i have some more exploring to do and learning curve.forgive my ignorance here but this is my first rv.i did have a old ford econoline camper i got rid of.i have a Carson toyhauler and this gmc currently.perhaps the rattler system in the back is the buzz box?only id here it running only when raising or lowering my airbag system??
My intial query here is when i bought the gmc the shop said i had a drain on the charging system.now i come to think it may have been missed diagnosed?couse the bullitin in the article states the pre 76 have a flaw where the alternator light stays on full time.and it listed the possible fixes aswell.
I appreaciate the help
http://www.gmcmotorhome.info/engine.html#alternator
Gmc76Birchaven 23'94947
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| Re: Hmn power drain? [message #70846 is a reply to message #70805] |
Thu, 14 January 2010 23:33 |
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gmcdude76
Messages: 102
Registered: December 2009
Location: Northern Ca
Karma: 1
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Senior Member |
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Every GMC Motorhome should have the APC assembly. Even the 1977/78 models do not protect the Nichrome Resistance Wire!
GMC published a Tech Note in 1974 to identify a problem that let the alternator light glow dimly on most GMC Motorhomes’. The reverse voltage glow did not cause any damage, but GMC did modify their production in 1977/78 models of the GMC Motorhome to eliminate the condition. The “Fix” eliminated the reverse voltage problem for the alternator light but did not protect the Nichrome resistance wire that runs in a wire bundle from the fuse block behind the glove box, to behind the instrument panel.
When a high reverse voltage occurs due to a battery isolator or alternator failure, the Nichrome wire can melt the insulation on wires in the wire bundle. This event has even started fires behind the dashboard.
The Alternator Protection Cable protects against the damage that a high reverse voltage would do to the alternator light and the Nichrome wire. The APC uses the GMC solution to the problem but also protects the Nichrome Resistance Wire. Any GMC owner can install the APC. The original two-conductor cable is unplugged from the alternator and plugged into the APC assembly. The APC assembly is then plugged into the alternator. This completes the installation.
Gmc76Birchaven 23'94947
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| Re: Hmn power drain? [message #70849 is a reply to message #70843] |
Fri, 15 January 2010 03:41 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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The Buzz box is a large normally gray box that is connected to the house fuse panel by a relatively large gauge wire. It is connected to a 120vac outlet (normal house type convenience plug) and makes a steady "buzzing" sound during operation. It is possible that it has been removed and hopefully replaced, before you got your rig. Here is a picture of Rob's: <http://www.gmcmhphotos.com/photos/showphoto.php?photo=10717&cat=3953> The album also shows a popular replacement... there ARE other brands and styles so yours may not look like JUST like Rob's.
I suspect your converter (buzz box or other) is in the "electrical stuff" under the closet.
| gmcdude76 wrote on Thu, 14 January 2010 20:25 |
... also i looked today with a friend and there isent a buz box under the sink?the only thing that is under my sink is part of the furnice line.
The fuse box and electrical stuff is under the closet on the passenger side. ...
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But back to your battery drain problem. I had assumed we were talking the house system. But what ever the battery, does it hold a charge when totally disconnected?
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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