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Old 05-01-2024, 09:32 AM   #1
2 Rivet Member
 
1977 21' Globetrotter
Edmonton , AB
Join Date: May 2022
Posts: 21
Images: 4
Replacing DC panel on 77 Land Yacht

Hi there I am hoping I can get some advice on replacing the DC panel of my !977 Land Yacht.
I have been having some issues with poor connections and I either have to take everything apart and clean the contacts or replace it. Given that the wiring has to be changed (Apparently the 1977 standard was for the center pin of the 7 pin harness to be the charge line and now it is for the back up lights...) I think the best option would be to replace it. The question I have is that as far as I can see there aren't any single panels that I could use for the interior DC and the exterior light DC panels so I thought I could use a 5 circuit panel like the Blue Sea 8081 for the interior DC and then a simple 4 way DC circuit board for the exterior lights.
Does this seem reasonable? I would need to connect the converter, a single battery as well as the TV charge line. I would assume that the converter would connect to the "from DC positive and to DC negative" contacts on the bottom of the wiring diagram. The battery positive contact is obvious although it isn't so clear where to make the battery negative connection. I am guessing either to the same point as the converter or to the second "to DC negative" on the left side of the diagram.
The other question I have is where to connect the TV charge line. Would this be to the same contact as the other batteries or would it be better to connect to the "from device positive" contact on the left middle of the diagram.
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Old 05-01-2024, 09:44 AM   #2
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1977 21' Globetrotter
Edmonton , AB
Join Date: May 2022
Posts: 21
Images: 4
One last question. I would also need to connect the electric hoist. I thought that I could add it to one of the other circuits. Or I could find a 6 circuit panel instead of the 5 circuit one. I wouldn't think their would be too much of problem adding it to another circuit as I don't see any reason to be using the hoist at the same time as anything else aside for the DC mode of the refridgerator.
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Old 05-02-2024, 09:32 AM   #3
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1976 Argosy 24
1961 28' Ambassador
1968 26' Overlander
Lakewood , Colorado
Join Date: Jun 2014
Posts: 426
Hello, good project going there. I like the Blue Sea 5026, 12 circuit with built in pos/neg bus bars. Very versatile and expandable. I think the little 4 fuse block would be fine for the lights or use a different wiring block for where the 7 wire harness connects to the trailer for ease of wire connection. You may also want to consider both pos. and neg. buss bars as the amount and gauge of wiring expands. Loads of info about this on the forums. Be aware of your wiring lengths and corresponding wire gauges.
Good luck, Mark D
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Old 05-02-2024, 03:33 PM   #4
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1977 21' Globetrotter
Edmonton , AB
Join Date: May 2022
Posts: 21
Images: 4
Hey Mark I really appreciate your response.

Not sure if you are able to help with this but as I am planning this project I am trying to make sense of the wiring as far as I can tell the 1977 7 pin wiring is different from the current standard. Specifically for my 1977 RV the center pin is for the charge and it now seems that center pin is for the reverse lights. Does this make sense? I can switch the black and blue wires when I connect the new panel to get the correct wiring. The only issue is that the blue wire is a larger gage than the black wire presumably to allow a higher current for charging. Not sure if there would be an issue using the smaller gage wire for the charge line, presumably I would end up with slower charging.

The other question I have is related to the electric hoist (which is the orange wire ). Not quite sure why but the wiring of my RV is different from the wiring diagram with an extra black wire connecting to the circuit breakers. I will need to do some testing but I am guessing that the black wire is either a connection to to black wire from the 7 pin harness (this would correct for the change from the old standard, although not sure why they would keep the blue wire in the circuit) or the black wire could come off of one of the interior circuits to power the hoist from the RV battery / converter.
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Old 05-03-2024, 09:42 AM   #5
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1976 Argosy 24
1961 28' Ambassador
1968 26' Overlander
Lakewood , Colorado
Join Date: Jun 2014
Posts: 426
As many before you you have discovered that the wiring for the 7 wire harness is different form modern to 50 years ago. I like to use the junction box I mentioned as an easy and secure way to connect a new harness to the existing trailer wiring. The trailer light wiring is usually the same, the differences come in the charge wire, trailer brake wire (often light blue in the tow vehicle) and the back up lights. I am always most concerned with the trailer brake wiring. Wire gauge will certainly make a big difference in the charging capability from the TV. Common current practice is to install a DC to DC charge controller along with a separate, much larger gauge 2 wire harness, think 6 or even 4 AWG. Lots of posts on this on the forums. I did it and it's great. I use my vehicles to tow several rigs so they all need to match. Usually ends up being at the tongue of the trailer with a test light checking the wiring.
Most of my trailers are total re-wires and I've never had a power jack (yet) but I would be running a new, bigger, separate fused wire to the jack, maybe splitting off for the emergency brake switch.
Good luck, Mark D
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Old 05-03-2024, 10:39 AM   #6
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1977 21' Globetrotter
Edmonton , AB
Join Date: May 2022
Posts: 21
Images: 4
Thanks again Mark. I really appreciate your help and I am pretty sure I have a pretty clear plan to start. I ended up buying a Parallax DC panel based on what a different member had posted. Plan on doing some testing over the weekend of my TV and RV to make sure I understand exactly what is what and then hopefully things will go reasonably smoothly once the panel arrives.
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Old 06-14-2024, 07:34 AM   #7
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1977 21' Globetrotter
Edmonton , AB
Join Date: May 2022
Posts: 21
Images: 4
More DC circuit questions

Hi Mark I am just getting started on replacing my DC circuit board and am a bit puzzled by the wiring I have found. Specifically there seems to be an extra wire (blue) coming off of the electric brake box. There is a yellow wire off the 7 pin harness connected to the brake box as expected but then there is a blue wire off of the box that then connects to the circuit breaker that powers the electric winch. For the winch there is another blue wire coming off the 7 pin harness and the wire from the RV circuit board which I understand but I really can't think of why there is a third wire coming off of the brake box connected to the winch circuit.
I would really appreciate any ideas of why my RV is wired this way. At the moment I am thinking that I probably will start with the plan of not connecting the blue wire from the brake box. As far as I can see it is not part of the original wiring plan.
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Old 06-14-2024, 10:13 AM   #8
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1988 32' Excella
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That wire is probably for the emergency breakaway safety switch. This is a mandatory by law way to activate the brakes if the trailer separates from the TV.
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Old 06-14-2024, 04:10 PM   #9
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1977 21' Globetrotter
Edmonton , AB
Join Date: May 2022
Posts: 21
Images: 4
Hi there thanks for your response. There are two black wires that leave the brake box and then go under the box that are connected to the switch to activate if the trailer is separated from the tow vehicle so I don't think that the blue wire is involved in the emergency brake response. What is puzzling me is that this blue wire seems to be providing power to the electric winch on the DC circuit board. Really can't figure out why it is there as there is already a connection between the RV battery and the TV auxillary line.
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Old 06-15-2024, 09:53 AM   #10
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1976 Argosy 24
1961 28' Ambassador
1968 26' Overlander
Lakewood , Colorado
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Posts: 426
Hey, so here is where it gets challenging not seeing it in person. Pic #4 with the hydraulic lines makes me wonder exactly what kinds of brakes the trailer has. This will most likely impact the wiring. I believe in most modern rigs the winch and breakaway switch wiring is all contained in the trailer with only incidental connection to the rest of the wiring. Also remember that 50 years on some of the wire colors have changed along with pin position in the harness. I'd like to know what's in that box on the tongue, is that what you're calling the brake box? That could be an aftermarket addition of electric over hydraulic disc brakes. Maybe. Also, after 50 odd years it can be challenging to figure out what someone else did. I often end up tracing and testing for continuity to figure out exactly what is connected to what. Post a pic of the inside of that box if you want. Good luck, Mark D
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Old 06-15-2024, 11:34 AM   #11
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1988 32' Excella
Robbinsville , New Jersey
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Quote:
Originally Posted by mrdes8 View Post
Hey, so here is where it gets challenging not seeing it in person. Pic #4 with the hydraulic lines makes me wonder exactly what kinds of brakes the trailer has. This will most likely impact the wiring. I believe in most modern rigs the winch and breakaway switch wiring is all contained in the trailer with only incidental connection to the rest of the wiring. Also remember that 50 years on some of the wire colors have changed along with pin position in the harness. I'd like to know what's in that box on the tongue, is that what you're calling the brake box? That could be an aftermarket addition of electric over hydraulic disc brakes. Maybe. Also, after 50 odd years it can be challenging to figure out what someone else did. I often end up tracing and testing for continuity to figure out exactly what is connected to what. Post a pic of the inside of that box if you want. Good luck, Mark D
Now that you mention that, some 1977 Airstreams came with vacuum over hydraulic brakes from the factory. Since this system is not compatible with modern vehicles it would need to be modified to work, usually converted to electric over hydraulic or completely replaced.
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Old 06-17-2024, 04:43 PM   #12
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1977 21' Globetrotter
Edmonton , AB
Join Date: May 2022
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Thanks again for all of the help.

So I have attached a few more pictures. First infront of the metal box is the plastic box with the Bargman Breakaway System label. In this box is a battery with black, blue and a white wire attached).

I also have a wiring diagram for the Brake Controller from the 1977 Service Manual. On this diagram the controller receives yellow, blue white wires (which is what my RV has), although there is also a red wire from the brake switch which I don't have.

We used the trailer last year and the brakes seemed to work well (hardly noticed the trailer behind us) so however it was set up seemed to be correct.

The blue wire to the brake controller was attached to the circuit with the hoist (which had the blue auxillary wire from the 7 pin harness as well as a connection to the RV battery). I have attached a photo of my new DC distribution panel. I can connect the blue wire to the brake controller to one of my 11 poles for the distribution board which receives power from the TV and RV. As the original circuit had 30a circuit breakers I would plan on using a 30a fuse (like I did for the hoist).

Does this make sense?
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Old 06-18-2024, 05:04 PM   #13
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1977 21' Globetrotter
Edmonton , AB
Join Date: May 2022
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So a bit more information.

Mark, you are correct that I have hydraulic brakes. and I am pretty sure that Wasbro is right that the metal box is the electric over hydraulic that replaced the original vacuum system.

I bought this trailer about 1/4 way through a reno from a friend who had purchased it 20 years ago so I can't say I have all the details on the trailer. I do have the 1977 Service Manual and along with the brake details for the original vacuum system, it also describes an antisway system which also works off of the yellow wire from the 7 pin harness as well as the blue wire with connections to the 7 pin harness auxillary and the RV battery. No idea of whether my trailer has the antisway system or how a 1977 antisway system would work. I would have to do a fair bit of dissassembly to get into the metal box on the yolk and really not keen to take off the belly pan to see what is underneath. At the end of the day I was pleasantly surprised at how easy the trailer was to tow so I think I am going to leave a bit of mystery in the details and keep everything connected as it originally was.
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