Electrical Problems 1979 Beachcomber - Fiberglass RV

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Old 07-03-2006, 04:17 PM   #1
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Trailer: Beachcomber
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I'm hoping that someone may be able to help me to solve some elctrical issues that I am having with my trailer.


1. When turning on right signal light both right and left signals blink.

2. Although I have electrical power to the fridge and plugs, I have no power to interior lights.

3. Converter has 5 loose wires (see image) and I have no idea where they go.

If anyone can help solve my problems I would rteally appreciate it!!


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Old 07-03-2006, 06:53 PM   #2
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Trailer: 2002 19 ft Scamp 19 ft 5th Wheel
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1. When turning on right signal light both right and left signals blink.

This is a separate system that connects to the tow vehicle and sounds like a ground problem. Ground the tow vehicle receptacle white wire to a bare spot on the tow vehicle frame and ground the white wire on the trailer plug to a bare spot on the trailer frame and ground each tail light to a bare spot on the trailer frame. (That is assuming that you have a correctly wired receptacle and plug)

2. Although I have electrical power to the fridge and plugs, I have no power to interior lights.

R U talking about 120Volt electrical power or 12V DC?

3. Converter has 5 loose wires (see image) and I have no idea where they go.

I suggest that you get on the Internet to see if you can get a schematic of the converter. Connecting wires without a schematic or knowing where they should go is a most dangerous thing to do.

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Old 07-03-2006, 07:47 PM   #3
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Trailer: Beachcomber
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Thanks for your help Darwin. I will try what you suggested for the signal lights.

As for the interior lights, I am only able to run off of 120V at the moment as the 12 V DC system was not usable when I purchased the trailer this Spring and I'm going to try and fix it at some point. The receptacle plugs and the fridge will work when I am plugged into 120V electrical service but none of the lights will.

I have tried to locate some information on the web about the converter but have had no luck yet. It is a Powertron converter and indicates that it was made in Winnipeg, Manitoba in 1979. There is no listing for that company that I can find other than in the UK. The two black and one red wire that you see me holding in the photo all are connected to what seems to be an electro-magnetic switch which is directly under my hand in the photo. In the center of the converter you will see two brown coloured wires that are just kind of hanging there. Any ideas as to what these may be for??

Thanks again for your help.

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Old 07-04-2006, 09:37 AM   #4
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Trailer: 2002 19 ft Scamp 19 ft 5th Wheel
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In our Scamp, all the lights are vehicle bulbs and run off 12V DC. Check your bulbs to see if that is what U have. We only have 1 AC light and it is floresent.

You could try to back engineer what the wires go to and accomplish however make sure nothing is pluged into live power. I use a toner to do this, apply the toner and go and look for a tone at various places until I find it.
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Old 07-04-2006, 09:50 AM   #5
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Trailer: 2002 19 ft Scamp 19 ft 5th Wheel
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I see the transformer in and it appears that the transformer out is 2 loose wires. The output would go to a bridge rectifier to make the DC. It appears that there is a hole in the unit with a circle appearing on the paint Is something missing? If something were missing, it would explain why you have loose wires.

If parts are missing it may be the best to just get a new converter.

Look at this site on Ebay and Send them an e mail as they often have used converters.

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Old 07-05-2006, 01:23 PM   #6
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Name: Brian
Trailer: Boler (B1700RGH) 1979
Posts: 5,000
That converter looks like the one in my 1979 B1700RGH. Mine is a Powertron RM 300D, also from Winnipeg. Unfortunately, it is the only original major component for which I did not receive a manual. My comments are based on my experience with my converter, which was gained without the benefit of any documentation.

I agree with Darwin that there seems to be something missing. From right to left in your photo, Ralph, I see the transformer, a space where my unit has a rectifier, the relay to switch between converter and battery power to the 12V circuits, and the circuit breakers.

My unit does not have a full bridge rectifier, which uses 4 diodes to convert AC power to DC; instead, there are two outputs from the transformer, with each one going through a diode so only the desired polarity of power is delivered. The two diodes are mounted on a large finned aluminum heat sink. Here's a photo - although it is from a different angle it looks like a match. Please note that I took this while replacing circuit breakers, so they are just hanging on their wires, not inserted as normal through the vertical series of mounting holes down the right (left in this view from the back) side of the front panel. Also note that the transformer output wires are soldered to the diodes, while Ralph's wires from his transformer appeared to have soldered; also, the other rectifier connections use eyelet terminals, like the other non-connected wires in Ralph's unit.

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The way mine is wired, if there is no AC power then the relay is in the position which connects the battery to the interior circuits, so a missing rectifier would not cause the loss of DC power to interior lights. I would check what is connected to the relay, and where that red wire might go (I'm guess the non-connected black ones are the negative side of the DC supply, like my grey wires, and the red is the positive output from the rectifier, but that would need to be confirmed). There was one point on my last trip during which it seemed that the relay failed to switch to battery, but I could not reproduce the problem, and upon examination the relay always springs back to battery power.

Edit: I realized that the relay comments may not be clear given the original angle of view, so here's a view from the other end, showing the relay.

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The grey wires on one corner of the relay are attached to the common terminal, and deliver power to the circuit breakers. The common terminal is connected to the arm which is pulled by the coil (blue cylinder) when the converter is on. Pulling the arm disconnects it from the battery contact at the bottom centre of the relay, and connects it instead to the converter output contact. So in conventional electrical terms, the battery contact is the NC (normally closed) contact and the converter output is the NO (normally open) contact. As long as the wiring is intact, when I follow the wire from the battery positive it goes to the NC terminal of the relay, through the relay to the common terminal, then on to the circuit breakers; this path is complete whenever there is no AC power to the converter, and thus none to the relay coil.
1979 Boler B1700RGH, pulled by 2004 Toyota Sienna LE 2WD
Information is good. Lack of information is not so good, but misinformation is much worse. Check facts, and apply common sense liberally.
STATUS: No longer active in forum.
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Old 07-09-2006, 11:32 AM   #7
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Trailer: Beachcomber
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Thanks for all of the info. My converter is a Powertron MDM 300D. A little different I suppose but very similar. Your information is helpful. The battery placement area on the tongue of the trailer has more or less been removed by previous owners. They must have disabled the entire system. It is an old trailer and I may just run it solely off of DC. There is always the option of putting in a new converter I suppose.

I did manage to get my signal lamps working now but am still having trouble with the interior lights.

Thanks alot again for your help
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Old 07-09-2006, 11:43 AM   #8
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Name: Gina D.
Trailer: '77 Leocraft 17 & Former Burro owner and fan!
West Coast USA
Posts: 9,010
Ralphie, I have no convertor at all and have not missed it.

I have a small charger that runs on AC attached to my battery, and an AC system for outlets ony.

The 12v stuff runs direct from the battery. While plugged in, battery charges, lights run off battery.. no problem.

When not plugged in, I charge off solar. This seems to work well for me. It might for you too, depending on your 12v needs.
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Old 06-27-2009, 03:46 PM   #9
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Trailer: Bigger 20 ft
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On my 77 Bigger with a Powertron RM300D converter it is overcharging the +12V Battery. It puts out 13.5V when NOT connected to the battery, but when a load is connected (ie connecting the battery) the output jumps to 17V DC (which appears to include a 30V AC portion). There should not be any AC IMO. I assume that the large silver heatsink are the power diodes to convert the 30V AC to 12V DC. The 120VAC / 12VDC relay appears to work. It has both AC circuit breakers and DC resettable fuses.

Areas of potential interest... shown in the attached picture
1. There is a potentiometer between the blue cap and orange wire in the encapsulated module.
Not sure what the module would do?

2. There is a three legged transistor(?) in the upper right corner that appears to be heat sinked to the metal frame (looks like a bolt). Assume that the white paste is a heat sink compound. It has a 0.7V differential between two of the leads. Far right lead output voltage can be adjusted with the pot mentioned above (~13V-15V).

3. There is a hard wire coil (inductor?) on the bottom right.

As an electronic tech, I am at a loss as to why the output is 17V when the battery is connected. Maybe it is the rogue AC signal making it's way to the DC circuitry causing the additional DC voltage.

ANY IDEAS what component to check or replace?
Keeping costs to a min are important, thus replacing the entire assembly is not an option unless I can get one local and cheap.
north Calgary
1977 Bigger 20' with bathroom
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