Home » Public Forums » GMCnet » Black or white? (pos or neg)
| Black or white? [message #364748] |
Wed, 16 June 2021 11:53  |
boybach
Messages: 566
Registered: December 2020
Location: Vancouver Island
Karma: 4
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After finding out the fridge in my coach was wired backwards and blew fuses and diodes every time it was hooked up, I was ready to correct the wiring problem but wasn't sure whether to swap the 12v feed wires at the fusebox or at the pigtail from the fridge.
Right now, in order to get the fridge running, I connected the pigtail from the control board at the fridge so that the black is positive and the red is negative ...not an ideal situation so I'd like to sort it out and correct the polarity so future owners won't have to go through what I had to. This fridge, even though about 10 years old, had NEVER worked. It is basically brand new and now works perfectly.
Question is: What wire coming to the fridge supposed to be + ? Is it the black or the white?
Is that the same system throughout the coach in the 12v system?
TIA
Larry
Larry - Victoria BC -
1977 ex-Palm Beach "Ol' Leaky" 40,000 miles, PO said everything working but forgot the word NOT. Atwood helium fridge, water heater & furnace. SS exhaust system, Onan, Iota Converter, R134A, New fuel lines & heat exchange hoses
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| [GMCnet] Re: Black or white? [message #364749 is a reply to message #364748] |
Wed, 16 June 2021 12:18  |
Lawrence Belland
Messages: 11
Registered: May 2021
Karma: 0
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Junior Member |
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The white wire is universally the "common" wire the black (or any other
color except green) carries the current. Green is the ground. If you ever
see a white wire that looks like it may be carrying power look along the
wire to see if black tape was wrapped around it. You can use a white wire
for power as long as you indicate the change. It should be marked at both
ends.
On Wed, Jun 16, 2021 at 9:53 AM wrote:
> After finding out the fridge in my coach was wired backwards and blew
> fuses and diodes every time it was hooked up, I was ready to correct the
> wiring
> problem but wasn't sure whether to swap the 12v feed wires at the fusebox
> or at the pigtail from the fridge.
> Right now, in order to get the fridge running, I connected the pigtail
> from the control board at the fridge so that the black is positive and the
> red
> is negative ...not an ideal situation so I'd like to sort it out and
> correct the polarity so future owners won't have to go through what I had
> to.
> This fridge, even though about 10 years old, had NEVER worked. It is
> basically brand new and now works perfectly.
>
> Question is: What wire coming to the fridge supposed to be + ? Is it the
> black or the white?
>
> Is that the same system throughout the coach in the 12v system?
>
> TIA
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the
> word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
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| [GMCnet] Re: Black or white? [message #364752 is a reply to message #364749] |
Wed, 16 June 2021 12:51 |
Stu Rasmussen
Messages: 130
Registered: January 2019
Location: Silverton, OR
Karma: 0
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Senior Member |
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Perusing the DC wiring diagram for my 76 Transmode Birchaven it
appears that BLACK is BATTERY NEGATIVE and goes to FRAME GROUND.
The confusion arises when you think of NEC wiring code for houses,
etc. that specifies white is neutral (common) (also gray can be
neutral) and black is HOT.
So, a prudent sparkie will carefully check what is and what isn't
before inadvertently connecting automotive wiring in the same manner
and color code with house wiring.
Particularly confusing since our coaches have both 12VDC and 120VAC
independent yet interconnected systems.
Stu
Quoting Lawrence Belland :
> The white wire is universally the "common" wire the black (or any other
> color except green) carries the current. Green is the ground. If you ever
> see a white wire that looks like it may be carrying power look along the
> wire to see if black tape was wrapped around it. You can use a white wire
> for power as long as you indicate the change. It should be marked at both
> ends.
>
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Stu Rasmussen W7QJ
Silverton, OR
'77 Birchaven
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| [GMCnet] Re: Black or white? [message #364754 is a reply to message #364751] |
Wed, 16 June 2021 12:48 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Test, test, and verify polarity and voltage. RV's are the worst hodge podge
mess you are likely to ever encounter. A mix of 240 volt AC, 120 voltAC, 12
voly DC. Polarity and color code often wrong. Schematics seldom match
actual conditions.
Jim Hupy
Salem, Oregon
On Wed, Jun 16, 2021, 10:40 AM Jon Roche wrote:
> not sure there is a good answer.
>
> usually red should be the + 12v.
>
> but when it comes to some more modern RV stuff, you will find that the
> black might be + and white ground.
>
> sometimes you need to trace it out. many times you have to pay
> attention. nice to label for future once you do find out.
>
>
>
>
> http://www.rv-project.com/resources/wirecodes.php#:~:text=Basically%2C%20each%20SOLID%20color%20represents,color%20represents%20a%20different%20circui t
> .
> --
> Jon Roche
> 75 palm beach
> EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
> St. Cloud, MN
> http://lqqkatjon.blogspot.com/
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| [GMCnet] Re: Black or white? [message #364758 is a reply to message #364748] |
Wed, 16 June 2021 16:23 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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This thread illustrates exactly why I have my Brother label maker handy any
time I work on GMC wiring. The flag labels I put on every wire I identify
save me a lot of errors and repeated tracing jobs. The Brother is
especially good because the tape comes in multiple colors. The printed
characters are thermally transferred from a black ribbon onto the base
color, then a transparent layer of tape is put on top of that -- all
"automatically" and perfectly. When applied as a "flag" by removing the
protective paper from the adhesive back of the base tape, the label is
there to stay. I've had them under my hood for 20 years with no noticeable
deterioration. Even when I intentionally tested them with a heat gun, the
printing was still legible until the base tape was completely shriveled
around it. And I don't even use the "heavy duty" tape. Can't beat that!
Ken H.
On Wed, Jun 16, 2021 at 12:53 PM wrote:
> After finding out the fridge in my coach was wired backwards and blew
> fuses and diodes every time it was hooked up, I was ready to correct the
> wiring
> problem but wasn't sure whether to swap the 12v feed wires at the fusebox
> or at the pigtail from the fridge.
> Right now, in order to get the fridge running, I connected the pigtail
> from the control board at the fridge so that the black is positive and the
> red
> is negative ...not an ideal situation so I'd like to sort it out and
> correct the polarity so future owners won't have to go through what I had
> to.
> This fridge, even though about 10 years old, had NEVER worked. It is
> basically brand new and now works perfectly.
>
> Question is: What wire coming to the fridge supposed to be + ? Is it the
> black or the white?
>
> Is that the same system throughout the coach in the 12v system?
>
> TIA
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach 40,000 miles, PO said everything working but forgot the
> word NOT. New Atwood fridge, water heater & furnace. New SS exhaust system,
> 6000w Onan, Iota Converter, R134A A/C, New fuel lines & heat exchange hoses
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] Re: Black or white? [message #364759 is a reply to message #364758] |
Wed, 16 June 2021 17:10 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Ken Henderson wrote on Wed, 16 June 2021 17:23This thread illustrates exactly why I have my Brother label maker handy any time I work on GMC wiring. The flag labels I put on every wire I identify save me a lot of errors and repeated tracing jobs. The Brother is especially good because the tape comes in multiple colors. The printed characters are thermally transferred from a black ribbon onto the base color, then a transparent layer of tape is put on top of that -- all "automatically" and perfectly. When applied as a "flag" by removing the protective paper from the adhesive back of the base tape, the label is there to stay. I've had them under my hood for 20 years with no noticeable deterioration. Even when I intentionally tested them with a heat gun, the
printing was still legible until the base tape was completely shriveled around it. And I don't even use the "heavy duty" tape. Can't beat that!
Ken H.
I very seldom disagree with anything Ken posts. This isn't going to be one of those times.....
The Brother labeler came aboard when I was just about full time doing boat work before the depression set in for the auto industry. I used it to relabel breaker and switch panels. The grand move there was that the machine I bought can be a printer for a computer. That meant that I could match the size and font on the existing panels. That was a real score to some owners. One owner almost accused me of not updating his panel....
Shortly after that, I was at a rally at Berrien Springs and I looked under the hood of a coach there and noticed how the owner had used that same label type to flag just about every wire in evidence. That idea stuck.
A real score to me was that the switch labels on the coach's instrument panel were fading and/or braking up. By going to the laptop (what I had it connected to) I could create a black background with white letters by reverse printing those labels. Yes, I have tape that make white letters on a black background, but they are not at all transparent.
Timing was always a bear so, I printed a picture of the timing scale copied right out of the manual and put it on the air filter housing for easy reference.
When working on the air for the rear suspension, I labeled every one of those plastic air lines and got them back together right on the first try.
I even numbered the spark plug wires. After how many years, so still exist, but they were not a great success everything else has been.
If you are doing serious work or might some day do serious work on your coach, go out and buy a label maker as soon as you can.
There is a very flexible 18mm tape for electric wire labeling. It does not work as well as hoped on most of the GMC sized wires. Big stuff is OK.
If you are ever sitting near Ken, ask him about his friends idea of labeling wires.....
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Re: Black or white? [message #364760 is a reply to message #364759] |
Wed, 16 June 2021 17:15 |
mghamms
Messages: 466
Registered: March 2016
Location: Ware, Massachusetts
Karma: 2
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Senior Member |
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I learned to test everything and to expect the unexpected.
When I changed to radio that didn't work when i bought my GMC I don't think any of the wires were correct.
Tested every wire ground + and speaker wires before wiring up the new unit.
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts
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| Re: Black or white? [message #364762 is a reply to message #364748] |
Wed, 16 June 2021 18:24 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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When it comes to DC and no Red is present all bets are off. That’s why the Evans heater booster fans behind the the stove ran backwards on many GM coaches.
John Lebetski
Woodstock, IL
77 Eleganza II
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| [GMCnet] Re: Black or white? [message #364763 is a reply to message #364762] |
Wed, 16 June 2021 21:22 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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In my X-Birchaven, fitted out by Coachmen, all the DC wiring was White for
Ground and either Blue or Green for +12 VDC. :-( And, I'm almost ashamed
to admit, still is, 'cause the wire was all 10-12 gauge and in excellent
condition, so I reused it when I gutted and rebuilt the interior. :-(
Ken H.
On Wed, Jun 16, 2021 at 7:24 PM John R. Lebetski
wrote:
> When it comes to DC and no Red is present all bets are off. That’s why
> the Evans heater booster fans behind the the stove ran backwards on many GM
> coaches.
> --
> John Lebetski
> Woodstock, IL
> 77 Eleganza II
> _______________________________________________
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> Unsubscribe or Change List Options:
>
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GMCnet mailing list
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: Black or white? [message #364767 is a reply to message #364748] |
Wed, 16 June 2021 23:26 |
boybach
Messages: 566
Registered: December 2020
Location: Vancouver Island
Karma: 4
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Senior Member |
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So I opened up the pigtail plug and switched the wires there and at the control board. I had some red and black electrical tape and tagged the coach black and white feed. Job done.
Larry
Larry - Victoria BC -
1977 ex-Palm Beach "Ol' Leaky" 40,000 miles, PO said everything working but forgot the word NOT. Atwood helium fridge, water heater & furnace. SS exhaust system, Onan, Iota Converter, R134A, New fuel lines & heat exchange hoses
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| Re: Black or white? [message #364774 is a reply to message #364748] |
Thu, 17 June 2021 08:09 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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As someone said "it depends". I hae found on my early '74:
- The chassis 12v wiring (vehicle related stuff) installed by GM the negative is black. White is a switched wire such as from brake switch to the turn-signal switch. GM seems to have used some common color codes across the lines. For instance the color codes on the GMCMH are the same as my '75 vette. Get the wiring diagram for your year coach. Get one as large as you can so you can read the small print. If you are not "electrical" the diagrams are still useable. Think of them like a road map. Follow the "road" to find out where a wire goes, its color. What it connects to will indicate its function. Color codes are part of this drawing.
- 120VAC GM installed coach wiring follows NEC. That is White is the neutral. Black or Red is hot. green is ground.
- For the coach 12v wiring all bets are off. If your MH coach wiring was installed by GM the wiring diagram for the house wiring will show the color codes. Do not trust other up-fitters wiring diagrams for color. Test.
After market 12v stuff I have found is relatively consistent. If the leads are red and black then the black is negative. If red and white the white is negative. Black and white good luck.. One warning that was noted here is things like clearance lights, aisle lights, are not polarity sensitive and could be wired either way. LED's are polarity sensitive and the correct lead must go to negative. See the note prior note on colors. I have yet to find one that does not follow this convention.
Basic instruction as noted by others. Don't assume. Always check with a meter. GM did theres their way, up-fitters did it their way. Who knows what the PO did.
Bottom line is if you have questions ask them here. You will get a correct answer. Maybe more than one. <grin>
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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