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| [GMCnet] 12V ground house and chassis [message #212792] |
Sat, 29 June 2013 23:17  |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
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Do both the chassis and house 12V systems ground through the body and frame? I've just installed a Maxx fan and simply grounded it to the aluminum rib.
Larry Davick
A Mystery Machine
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] 12V ground house and chassis [message #212794 is a reply to message #212792] |
Sun, 30 June 2013 00:09  |
drdonaldg
Messages: 35
Registered: June 2013
Location: San Rafael, CA
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The engine battery is grounded to the chassis or frame, the house battery is grounded to the body. There are several straps connecting the body to the frame so everything is interconnected. Attaching a ground to a rib or body stringer is what GMC did, and if done properly works well. Technically it is better to run a dedicated ground wire to a common ground, but personally I don't think that is necessary.
1977 Palm Beach
TZE167V100274
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| Re: [GMCnet] 12V ground house and chassis [message #212800 is a reply to message #212794] |
Sun, 30 June 2013 00:40 |
mickeysss
Messages: 1476
Registered: January 2012
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check out ken burtons seminar on grounds i think it was.
go direct from the battery ground to the motor only not the frame.
all house grounds go to the aluminum frame. keep them bright.
find his seminar, great stuff.
mick, palm beach, anaheim ca. 1977 date of origin.
On Jun 29, 2013, at 10:09 PM, Donald W. Guttman wrote:
>
>
> The engine battery is grounded to the chassis or frame, the house battery is grounded to the body. There are several straps connecting the body to the frame so everything is interconnected. Attaching a ground to a rib or body stringer is what GMC did, and if done properly works well. Technically it is better to run a dedicated ground wire to a common ground, but personally I don't think that is necessary.
> --
> 1977 Palm Beach
> TZE167V100274
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| Re: [GMCnet] 12V ground house and chassis [message #212801 is a reply to message #212794] |
Sun, 30 June 2013 00:51 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
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Thanks. For some reason I couldn't remember and probably was too lazy to look it up. My Fantastic fan the was installed by my Beloved PO was grounded at the 110VAC box in the ceiling.
I crimped a loop lug onto the ground, buffed up a rib, and screwed it in place with a little bulb grease. It still works great, but for the life of me I can't imagine what he had in mind.
Larry Davick
On Jun 29, 2013, at 10:09 PM, Donald W. Guttman <drdonaldg@aol.com> wrote:
>
>
> The engine battery is grounded to the chassis or frame, the house battery is grounded to the body. There are several straps connecting the body to the frame so everything is interconnected. Attaching a ground to a rib or body stringer is what GMC did, and if done properly works well. Technically it is better to run a dedicated ground wire to a common ground, but personally I don't think that is necessary.
> --
> 1977 Palm Beach
> TZE167V100274
> _______________________________________________
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Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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| Re: [GMCnet] 12V ground house and chassis [message #212808 is a reply to message #212807] |
Sun, 30 June 2013 04:23 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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You are welcome. Someone at GMC Eastern States asked me to put that together for a rally a few years back. I gave it once at that rally and once later at a GMCMI rally in Louisiana.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] 12V ground house and chassis [message #212809 is a reply to message #212808] |
Sun, 30 June 2013 04:28 |
Guy Lopes
Messages: 499
Registered: April 2004
Location: Sacramento, CA
Karma: 3
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I just returned home from a trip. Three days away from my computer and I had
about 340 emails from GMCnet. I love it!
Thanks Ken for that presentation. I'm printing it out now...
Guy in Sacramento
76 Birchaven
-----Original Message-----
From: gmclist-bounces@temp.gmcnet.org
[mailto:gmclist-bounces@temp.gmcnet.org] On Behalf Of Ken Burton
Sent: Sunday, June 30, 2013 2:24 AM
To: gmclist@temp.gmcnet.org
Subject: Re: [GMCnet] 12V ground house and chassis
ljdavick wrote on Sun, 30 June 2013 03:39
> Thanks, Ken. That's helpful.
>
> Larry Davick
>
> On Jun 29, 2013, at 11:23 PM, Ken Burton <n9cv@comcast.net> wrote:
>
> >
> >
> > http://www.gmceast.com/technical/Burton_Grounding_GMC_Motorhome.pdf
> > --
> > Ken Burton - N9KB
You are welcome. Someone at GMC Eastern States asked me to put that
together for a rally a few years back. I gave it once at that rally and
once later at a GMCMI rally in Louisiana.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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Guy Lopes
76 Birchaven "Orion"
Sacramento, CA
W6TOL
www.GMC-Guy.com
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| Re: [GMCnet] 12V ground house and chassis [message #212859 is a reply to message #212808] |
Sun, 30 June 2013 14:28 |
George B.
Messages: 213
Registered: February 2012
Karma: 1
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Ken: Thank you for the great information.
Two questions
(1) I have a 2/0 cable going from my starting battery negative terminal directly to the engine block and a second #4, I think, cable going from the same negative terminal to the frame.
Are you saying the second smaller (-) cable going to the frame is not necessary and I should remove it? (the original frame to body braided straps are in place)
(2) Also, the PO re-did the interior and installed 3 big terminal strips, interconnected with #4 wire, for grounding the 12 volt house equipment. One behind the drivers seat connects the converter to the aluminum body. That strip is then connected to a 2nd strip, in the compartment behind the refrigerator, where several device grounds are connected to it. From there it is connected to the 3rd strip under the rear bed that grounds the remainder of the equipment such as fans, pumps and dc lights. That 3rd ground terminal is then connected directly to the house battery (-) terminal. Thus, each device has a dedicated (+) & (-) wire to it. There is a positive terminal strip at each location too. Essentially it is like a house AC system with 3 sub panels. Is all of that grounding wire excess and should have each device been grounded directly to the nearest body aluminum frame member? If so is the correction worth the effort? (My coach does not have a genset)
George Butts
Las Vegas Nevada
73 "Custom 26' Q" & 76 23' Birchaven
71 Honda 600 Coupe & 01 Tracker Toads
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| Re: [GMCnet] 12V ground house and chassis [message #212905 is a reply to message #212859] |
Sun, 30 June 2013 22:43 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| George B. wrote on Sun, 30 June 2013 14:28 |
Ken: Thank you for the great information.
Two questions
(1) I have a 2/0 cable going from my starting battery negative terminal directly to the engine block and a second #4, I think, cable going from the same negative terminal to the frame.
Are you saying the second smaller (-) cable going to the frame is not necessary and I should remove it? (the original frame to body braided straps are in place)
(2) Also, the PO re-did the interior and installed 3 big terminal strips, interconnected with #4 wire, for grounding the 12 volt house equipment. One behind the drivers seat connects the converter to the aluminum body. That strip is then connected to a 2nd strip, in the compartment behind the refrigerator, where several device grounds are connected to it. From there it is connected to the 3rd strip under the rear bed that grounds the remainder of the equipment such as fans, pumps and dc lights. That 3rd ground terminal is then connected directly to the house battery (-) terminal. Thus, each device has a dedicated (+) & (-) wire to it. There is a positive terminal strip at each location too. Essentially it is like a house AC system with 3 sub panels. Is all of that grounding wire excess and should have each device been grounded directly to the nearest body aluminum frame member? If so is the correction worth the effort? (My coach does not have a genset)
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Wow! I wonder at today's prices how much all that extra copper is worth.
(1) The second #4 going battery to the frame is unnecessary. The thing to remember is the battery basically powers nothing except the starter. The engine side of the coach is powered by the alternator and the engine block with attached transmission and Final Drive is the master ground for that system.
What is the purpose of the #4 connected to the frame? I have no idea what he was thinking. There is already a direct jumper from the master ground to the frame. It is a braided strap on the back of the trans (still part of the master ground) direct to the frame. So what you have is a set of parallel connections. One is direct and one is master ground to the battery and then the battery to the frame.
When you set up parallel paths you run the risk of establishing ground loops. Ground loops become antennas at some unknown frequency and can cause noise problems. That said, If you are not experiencing noise problems then it probably will not hurt to leave it installed.
(2) The master ground for the body it the aluminum frame itself. All of these extra terminal strips mounted around the coach with #4 connecting cables do nothing but lengthen the path back to the house master ground. I can not figure out what he was thinking. Again, it was all unnecessary but if it works, you probably can leave it that way. I personally would have used the aluminum body for ground just like GM designed it.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] 12V ground house and chassis [message #212914 is a reply to message #212905] |
Mon, 01 July 2013 04:33 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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| Ken Burton wrote on Sun, 30 June 2013 22:43 |
Wow! I wonder at today's prices how much all that extra copper is worth.
(1) The second #4 going battery to the frame is unnecessary. The thing to remember is the battery basically powers nothing except the starter. The engine side of the coach is powered by the alternator and the engine block with attached transmission and Final Drive is the master ground for that system.
What is the purpose of the #4 connected to the frame? I have no idea what he was thinking. There is already a direct jumper from the master ground to the frame. It is a braided strap on the back of the trans (still part of the master ground) direct to the frame. So what you have is a set of parallel connections. One is direct and one is master ground to the battery and then the battery to the frame.
When you set up parallel paths you run the risk of establishing ground loops. Ground loops become antennas at some unknown frequency and can cause noise problems. That said, If you are not experiencing noise problems then it probably will not hurt to leave it installed.
(2) The master ground for the body it the aluminum frame itself. All of these extra terminal strips mounted around the coach with #4 connecting cables do nothing but lengthen the path back to the house master ground. I can not figure out what he was thinking. Again, it was all unnecessary but if it works, you probably can leave it that way. I personally would have used the aluminum body for ground just like GM designed it.
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I agree with what Ken says IF your OEM ground straps are in good condition!
Mine were not. Pictures here:
http://www.gmcmhphotos.com/photos/g6081-frame-ground-connections-1974.html
As shown I have replaced mine. The engine to frame ground is very difficult to get off. I connected from the engine master ground bolt to the frame to replace that strap.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] 12V ground house and chassis [message #212986 is a reply to message #212915] |
Mon, 01 July 2013 20:17 |
George B.
Messages: 213
Registered: February 2012
Karma: 1
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Senior Member |
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Thanks Ken, Gene & all.
Great information. I don't think I will change anything, except where the house battery is grounded, just now as everything seems to work OK as is....for now. Only I do have to figure out some other electrical mysteries left by the PO as in switches and gauges I am not sure of. However that is some of the fun of these coaches, a surprise a day.
George Butts
Las Vegas Nevada
73 "Custom 26' Q" & 76 23' Birchaven
71 Honda 600 Coupe & 01 Tracker Toads
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| Re: [GMCnet] 12V ground house and chassis [message #212992 is a reply to message #212915] |
Mon, 01 July 2013 23:08 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| Mr ERFisher wrote on Mon, 01 July 2013 06:25 |
STARTER
- the starter draws 300 amps, (needs to be wired directly to the battery
(plus and ground)
http://www.gmcmhphotos.com/photos/g5493-gmc-cranking-improve-for-free.html
- the engine is mother-ground,
-- everything else needs the ground cable from the engine to the frame
-- the dash ground should go to the engine (or as close as possible)
-- the distributor needs a ground to the block
-- the curse control needs a ground to the block
-- the alternator needs a ground to the block
-
jwid
gene
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Let's discuss some of these.
The cruise control is powered by the engine system but GM erroneously hooked it's ground to the body. To get back to the master ground (the engine) the CC current has to flow through both of those crossover straps and the frame. If you have cruise electrical problems, it is probably caused by one of the crossover jumpers. I have been suggesting that the cruise control ground lead be disconnected from the body and reattached to any bolt on the rear of the engine bypassing those jumpers. I have fixed several cruise control problems for people by moving the CC ground to the engine.
The distributor gets it's ground by being mounted to the engine. Unfortunately the distributor is an aluminum alloy and over time it corrodes where it touches / mounts to the engine. The causes ignition electrical problems. Dick Paterson, when he rebuilds a distributor, adds a terminal on the bottom of the distributor for an additional ground connection. I am suggesting that a small wire be run from that terminal to the back of the engine. This will bypass that corrosion point.
The alternator is already grounded to the block by nature of its multiple mounting bolts. Nothing additional is need for it.
The dash ground takes a strange multi-hop route. It runs from the dash to the aluminum plate with the isolator on it. Then ir runs from the aluminum plate to the battery and finally from the battery to the engine. Gene's suggestion of running a replacement ground wire from the dash to the engine block is a good one. The added / replacement wire eliminates all of those extra hops and connections.
-- everything else needs the ground cable from the engine to the frame
I do not understand gene's above statement. Everything powered by the engine gets it's ground from the engine. Nothing powered by the engine 12 volt system gets it's ground by attaching to the frame.
Now for the exceptions. A couple of items powered by the engine do get their ground by traveling through the engine to frame and aluminum body to frame crossover straps. This happens because these items are grounded to the coach aluminum body. The two I can think of are the cruise control and charging of the house batteries by the engine driven alternator. The last item I can think of would be using the boost switch to start the engine using the house batteries.
When thinking of the ground systems on the GMC simply think of two independent systems. If necessary for visualization purposes, picture the coach body removed from the frame and drive train. Now one ground system is the house aluminum frame for the removed body and the other is the engine for the engine/drive train.frame system. The both work independently of each other.
To make a rolling GMC reinstall the coach body to the frame and install two jumpers between the body and the frame and the engine and the frame. Note: there is a 3rd jumper if you have an Onan installed.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] 12V ground house and chassis [message #213008 is a reply to message #212992] |
Tue, 02 July 2013 03:20 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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Senior Member |
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>
> Let's discuss some of these.
>
> The cruise control is powered by the engine system but GM erroneously
> hooked it's ground to the body. To get back to the master ground (the
> engine) the CC current has to flow through both of those crossover straps
> and the frame. If you have cruise electrical problems, it is probably
> caused by one of the crossover jumpers. I have been suggesting that the
> cruise control ground lead be disconnected from the body and reattached to
> any bolt on the rear of the engine bypassing those jumpers. I have fixed
> several cruise control problems for people by moving the CC ground to the
> engine.
>
see now, that is different, I was talking about the curse control.
- actually was the Rostra Cruise system, where Duane S. fount it was
sensitive to noise unless grounded to the engine...
>
> The distributor gets it's ground by being mounted to the engine.
> Unfortunately the distributor is an aluminum alloy and over time it
> corrodes where it touches / mounts to the engine. The causes ignition
> electrical problems. Dick Paterson, when he rebuilds a distributor, adds a
> terminal on the bottom of the distributor for an additional ground
> connection. I am suggesting that a small wire be run from that terminal to
> the back of the engine. This will bypass that corrosion point.
>
yep,Paterson jerked my chain on that also
>
> The alternator is already grounded to the block by nature of its multiple
> mounting bolts. Nothing additional is need for it.
>
Duane also found, (GaryBovee, ) that alternator put out a lot of electrical
noise, which was reduced with a ground wire to the engine
>
> The dash ground takes a strange multi-hop route. It runs from the dash to
> the aluminum plate with the isolator on it. Then ir runs from the aluminum
> plate to the battery and finally from the battery to the engine. Gene's
> suggestion of running a replacement ground wire from the dash to the engine
> block is a good one. The added / replacement wire eliminates all of those
> extra hops and connections.
>
>
> -- everything else needs the ground cable from the engine to the frame
>
> I do not understand gene's above statement. Everything powered by the
> engine gets it's ground from the engine. Nothing powered by the engine 12
> volt system gets it's ground by attaching to the frame.
>
> Now for the exceptions. A couple of items powered by the engine do get
> their ground by traveling through the engine to frame and aluminum body to
> frame crossover straps. This happens because these items are grounded to
> the coach aluminum body. The two I can think of are the cruise control and
> charging of the house batteries by the engine driven alternator. The last
> item I can think of would be using the boost switch to start the engine
> using the house batteries.
>
> When thinking of the ground systems on the GMC simply think of two
> independent systems. If necessary for visualization purposes, picture the
> coach body removed from the frame and drive train. Now one ground system
> is the house aluminum frame for the removed body and the other is the
> engine for the engine/drive train.frame system. The both work
> independently of each other.
>
is good thinking
>
> To make a rolling GMC reinstall the coach body to the frame and install
> two jumpers between the body and the frame and the engine and the frame.
> Note: there is a 3rd jumper if you have an Onan installed.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
> _______________________________________________
> GMCnet mailing list
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--
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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