| Electrical Separation Between Chassis Battery and House Battery [message #160701] |
Fri, 17 February 2012 16:25  |
A Hamilto
Messages: 4508
Registered: April 2011
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My 73 seems to be mostly unmodified. The house battery sits right next to the chassis battery in front of/under the passenger floorboard. When I took them out, I didn't pay any attention to how they were connected because I am smart enough to figure out how to put them back. Or so I thought.
One positive cable goes to the boost relay, and a cable goes from the same terminal back to the starter (through the starter solenoid probably). The other positive cable goes to the other side of the boost solenoid. One ground cable runs back and attaches to the engine. The other ground cable is bolted to the heavy frame that holds the radiator.
It seemed to me that the chassis battery positive should have the most direct route to the starter, so I connected it to the one that has the direct connection back to the starter solenoid. And the ground should be as direct a connection to the block as I can get.
When I hooked it up that way, the light over the sink and the exhaust fan over the stove came on.
I made sure the boost switch was set for "normal" and also tried the "boost" function. When I switched to "boost", the boost relay clicked. So I think it is working correctly. I set it back to "normal" and the relay released (at least it clicked again). When I turned the key, the starter turned the engine. When I connected the battery to the cable to (what I think is) the "house" side of the boost relay, turning the key had no effect.
Is there normally a connection between the house circuits and the chassis battery without setting the boost switch to "boost"?
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| Re: Electrical Separation Between Chassis Battery and House Battery [message #160706 is a reply to message #160701] |
Fri, 17 February 2012 17:10  |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
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A.
***Is there normally a connection between the house circuits and the chassis battery without setting the boost switch to "boost"?
My 1975 Glenbrook does not have a connection unless I hit the boost switch.
****.The other ground cable is bolted to the heavy frame that holds the radiator.
It seems you have both battery GNDs connected to the engine/chassis GND.
Is the house GND connected to the chassis GND?
I think there is another ground strap to tie the engine block GND to the house GND.
Regards,
Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: Electrical Separation Between Chassis Battery and House Battery [message #160707 is a reply to message #160706] |
Fri, 17 February 2012 17:45 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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| bwevers wrote on Fri, 17 February 2012 17:10 |
A.
***Is there normally a connection between the house circuits and the chassis battery without setting the boost switch to "boost"?
My 1975 Glenbrook does not have a connection unless I hit the boost switch.
****.The other ground cable is bolted to the heavy frame that holds the radiator.
It seems you have both battery GNDs connected to the engine/chassis GND.
Is the house GND connected to the chassis GND?
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I think the house should be grounded to the vehicle frame, which ultimately finds its way back to the radiator frame, and then through the cable back to the house battery neg terminal.| Quote: |
I think there is another ground strap to tie the engine block GND to the house GND.
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IMHO, there should be a strap from the engine to the frame. The engine is the ground center of the universe for the chassis battery. The frame is the ground for everything other than the engine (headlights, etc.). With the strap between the engine and frame, everything vehicle related finds its way back to the negative post of the chassis battery. With the cable from the radiator frame to the house battery, everything house related finds its way back to the house battery negative post.
Having said all that, I am pretty sure the grounding is fine. The path from the POSITIVE terminal of the chassis battery to the house circuits, with the boost switch off, is a mystery to me. It can't be right, because if so, the house stuff could drain the starter battery and leave me stranded.
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| Re: [GMCnet] Electrical Separation Between Chassis Battery and House Battery [message #160708 is a reply to message #160701] |
Fri, 17 February 2012 18:07 |
Richard Denney
Messages: 920
Registered: April 2010
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On Fri, Feb 17, 2012 at 5:25 PM, A. <markbb1@netzero.com> wrote:
> When I hooked it up [the correct] way, the light over the sink and the
> exhaust fan over the stove came on.
>
Have you checked the isolator? The isolator is a diode from the alternator
to the house circuits, and a diode from the alternator to the chassis
circuits. If the diode on the chassis side is shorted, hooking up the
chassis battery will power the house circuits, without the house battery
powering the chassis circuits.
The boost solenoid just bypasses the isolator with a high-current
connection. There are other ways to get from the chassis battery to the
house circuits.
If that isn't it, then I would look for non-factory wiring. My '73 was
wired so that both batteries were in parallel when I got it, but it took
quite a bit of wire-tracing to figure that out. If the isolator has failed,
someone may have moved wires or installed a jumper to bypass it. It's a
common trick to install a jumper between the outer terminals on an isolator
so that both batteries will charge on the converter (a combiner solves this
problem automatically), and someone may have just installed it from the
chassis terminal to the alternative (center) terminal.
Time for a test light!
Rick "who has spent a few hours here and there tracing circuits" Denney
--
'73 230 "Jaws"
Northern Virginia
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| Re: [GMCnet] Electrical Separation Between Chassis Battery and House Battery [message #160719 is a reply to message #160708] |
Fri, 17 February 2012 20:48 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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| Richard Denney wrote on Fri, 17 February 2012 18:07 |
Have you checked the isolator? The isolator is a diode from the alternator to the house circuits, and a diode from the alternator to the chassis circuits. If the diode on the chassis side is shorted, hooking up the chassis battery will power the house circuits, without the house battery powering the chassis circuits.
The boost solenoid just bypasses the isolator with a high-current connection. There are other ways to get from the chassis battery to the house circuits.
If that isn't it, then I would look for non-factory wiring. My '73 was wired so that both batteries were in parallel when I got it, but it took quite a bit of wire-tracing to figure that out. If the isolator has failed, someone may have moved wires or installed a jumper to bypass it. It's a common trick to install a jumper between the outer terminals on an isolator so that both batteries will charge on the converter (a combiner solves this problem automatically), and someone may have just installed it from the chassis terminal to the alternative (center) terminal.
Time for a test light!
Rick "who has spent a few hours here and there tracing circuits" Denney
--
'73 230 "Jaws"
Northern Virginia
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As much time as I have spent on this forum I should have been thinking about the isolator. Seems to me that diodes usually fail open, but there is probably that one in a thousand that fails closed.
I was thinking non-standard wiring (a jumper on the isolator would qualify).
I will chase it down as I get closer to taking a road trip in it. Right now I just have the battery disconnected when I am not working on it.
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| Re: Electrical Separation Between Chassis Battery and House Battery [message #160725 is a reply to message #160723] |
Fri, 17 February 2012 21:43 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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| JohnL455 wrote on Fri, 17 February 2012 21:35 |
My money goes on the PO mods.
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I'll second that.
BTW the ground connection between the engine and the frame is a woven ground strap around the right rear transmission mount. The body can flex enough to chew on this strap by the aluminum body frame rubbing on the transmission mount.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: Electrical Separation Between Chassis Battery and House Battery [message #160731 is a reply to message #160728] |
Fri, 17 February 2012 21:57 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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| ahamilto wrote on Fri, 17 February 2012 21:51 |
| midlf wrote on Fri, 17 February 2012 21:43 |
...the ground connection between the engine and the frame is a woven ground strap around the right rear transmission mount. The body can flex enough to chew on this strap by the aluminum body frame rubbing on the transmission mount.
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Mine might be broken. I had no headlights no matter how I had the battery connected. Does the ignition switch have to be on for the headlight switch to work?
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No, the ignition switch is not part of the headlight circuit. Lights should work any time the light switch is pulled on.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: Electrical Separation Between Chassis Battery and House Battery [message #160757 is a reply to message #160731] |
Sat, 18 February 2012 04:05 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| midlf wrote on Fri, 17 February 2012 21:57 |
| ahamilto wrote on Fri, 17 February 2012 21:51 |
| midlf wrote on Fri, 17 February 2012 21:43 |
...the ground connection between the engine and the frame is a woven ground strap around the right rear transmission mount. The body can flex enough to chew on this strap by the aluminum body frame rubbing on the transmission mount.
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Mine might be broken. I had no headlights no matter how I had the battery connected. Does the ignition switch have to be on for the headlight switch to work?
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No, the ignition switch is not part of the headlight circuit. Lights should work any time the light switch is pulled on.
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Here is a presentation I put together a few years back on Grounding. I gave it once at a GMC Eastern States rally and once at a GMCMI rally.
http://www.gmceast.com/technical/Burton_Grounding_GMC_Motorhome.pdf
The summary out of all of this is:
1. Consider the engine and the house as two separate systems. 2. The engine side battery negative side must be connected directly to a bolt on the engine block.
3. The house battery(s) negative should connect direct to the body (not the frame).
4. There are cross-connects between the engine and the body to allow charging of the house battery(s) by the engine alternator and also to enable the boost system. These cross connections use the vehicle frame as a common conductor.
These cross connects are:
1. a braided strap on the back of the transmission to the frame.
2. A braided strap from the frame to the body located across the front right body mount doughnut located just in front of the right front tire.
3. On vehicles with an Onan generator a braided strap between the body and the frame located in the left rear on the floor of the Onan compartment.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Electrical Separation Between Chassis Battery and House Battery [message #160949 is a reply to message #160769] |
Mon, 20 February 2012 01:21 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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On vehicles with front house batteries it is easy to have the ground connections connected to the wrong places. Check them.
If the grounds are all correct then I agree with you to start looking at the +12 sides. I would work on only the engine side or the house side first. I'd probably disconnect the house batteries and house connections to the isolator. Then start working on getting the engine side connected and working correctly. After that reverse the process and work on getting the house side correct. Suspect every connection as it has been 30+ years since GMC put it together. Who knows how many POs that may have known better than GM on how to do it and screwed it up along the way.
When both of those are working correctly on their own, then work on the cross connections like the isolator and boost relay.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] OT (was: Electrical Separation Between Chassis Battery and House Battery) [message #160995 is a reply to message #160969] |
Mon, 20 February 2012 11:23 |
tmaki
Messages: 200
Registered: September 2005
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On 2/20/2012 6:38 AM, A. wrote:
> work on the hall bathroom. That will take a few days of screwing
> drywall and smearing mud and tape and more mud and
> sanding and more mud and more sanding
Swerving a little OT with this but, if you don't already
have one, get one of the vacuum sanders that connect to a
vacuum (ShopVac, etc.) You will bless the day you spent $30
for it.
I just put in new ceilings, insulation, etc. in our 575 sq.
ft. family room, and sanded it the old-fashioned way. You
know what kind of mess it is. Bought the vac sander
attachment to do the rest of the drywall in the house, and
will never look back.
You do have to clean/change the filter in your vac quite
often, but you likely will not have to use a respirator or
mask, and you'll likely have less dust to clean up than you
have during a routine house cleaning.
Toby Maki
'73 Glacier 230
Riverside, CA
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| Re: [GMCnet] OT (was: Electrical Separation Between Chassis Battery and House Battery) [message #161014 is a reply to message #160995] |
Mon, 20 February 2012 15:46 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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| tmaki wrote on Mon, 20 February 2012 11:23 |
Swerving a little OT with this but, if you don't already have one, get one of the vacuum sanders that connect to a vacuum (ShopVac, etc.) You will bless the day you spent $30 for it.
I just put in new ceilings, insulation, etc. in our 575 sq. ft. family room, and sanded it the old-fashioned way. You know what kind of mess it is. Bought the vac sander attachment to do the rest of the drywall in the house, and will never look back.
You do have to clean/change the filter in your vac quite often, but you likely will not have to use a respirator or mask, and you'll likely have less dust to clean up than you have during a routine house cleaning.
Toby Maki
'73 Glacier 230
Riverside, CA
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I was planning on closing the door when sanding, and when the air gets too thick, take a break. Your proposal might reduce the number of breaks I have to take. Not necessarily desirable.
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| Re: [GMCnet] OT [message #161028 is a reply to message #161014] |
Mon, 20 February 2012 17:27 |
tmaki
Messages: 200
Registered: September 2005
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On 2/20/2012 1:46 PM, A. wrote:
>
>
> tmaki wrote on Mon, 20 February 2012 11:23
>> Swerving a little OT with this but, if you don't
>> already have one, get one of the vacuum sanders that
>> connect to a vacuum (ShopVac, etc.) You will bless the
>> day you spent $30 for it.
>> you'll likely have less dust to
>> clean up than you have during a routine house
>> cleaning.
>>
>>
> I was planning on closing the door when sanding, and when
> the air gets too thick, take a break. Your proposal
> might reduce the number of breaks I have to take. Not
> necessarily desirable.
Oh, it will reduce the breaks. For a bathroom, you might be
able to do all the sanding in one non-stop session if you
have a new filter on your vac.
Here's a link to the one I bought:
http://www.sportys.com/ToolShop/product/8285
If you need it today, you might find one at whatever home
improvement store is local to you.
Be sure to use the sanding screens and not sand paper. The
screens when used with a regular sanding tool are superior
to sand paper as the dust goes through instead of being
bound up in the grit. Muchomobetta.
Toby Maki
'73 Glacier 230
Riverside, CA
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