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Old 10-05-2017, 08:15 PM   #1
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1978 31' Sovereign
Brooklyn , New York
Join Date: Jul 2017
Posts: 32
Where to start with the 12V electrical system

I have a 78 Sovereign 31, I purchased it without any information about the electric system. It seems to have the old style converter, and the glass cylindrical fuses. i want to start testing out the 12v electrical system, and I'm trying to figure out where to start. Do I just hook up a battery and see which fuses blow? Perhaps put a continuity tester on the wires? Really have no idea how to start testing the electrical system.
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Old 10-06-2017, 10:12 AM   #2
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1973 21' Globetrotter
Houston , Texas
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A great way to start is to get a copy of the service manual for your year of trailer. I got one off of eBay, but there are other sources for "new" ones available. The serrvice manual will show you the color coding for the wires in your systems so that when you are testing, you know what circuit you are touching.

As for testing, the first thing I would do is turn off all of my switches and then check each 12V circuit to ground with an Ohm meter. This should identify any shorts to ground. If you find a short, and you know what that color of wire runs, then you can open up the fixture and have a look at what is coing on.

After that, you might put a battery in place and start checking to see what is working and what is not. If something (say a light bulb) is not working, you can start by checking the bulb, or put your volt meter on the wire and ensure you are getting current at the socket. IF no current, then that circuit diagram from the service manual will come in handy, as it will help you to know what all is daisy-chained together on that circuit, and may help you to identify where you are losing continuity.

Good luck!
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Old 10-06-2017, 10:55 AM   #3
Half a Rivet Short
 
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
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Hi

There are *lots* of ways to go about this. One of the many approaches:

First step is to start documenting what you have. Make some sort of drawing of the fuse panel. Start pulling the fuses and writing down what type and current rating each one is. They may (or may) not be correct. At least you will know what was there.

Next, as noted above, pull all the fuses and do some ohm meter checks. Be aware that some loads read fairly low resistance (A 12 amp DC load may read 1 ohm).

You can pop in a battery for the next step. A power supply is another alternative. If you happen to be able to borrow a current limited / metered supply, it might help a bit. Fuses go in one at a time and only one fuse in the panel at any one time. With the fuse in, see what does or does not come on / work.

Check off devices as you figure out what goes where. Colored dots are one approach. A big master drawing of everything is another approach. Accept that it's a multi pass process. You *will* have to go back a second or third time to find every last thing. If you have a metered supply, note what each circuit is pulling as you check it. A lightbulb tester is usually the fastest way to check what wire is or is not hot .....

Take a look at the dates on the batteries. If they are over 6 years old, replace them. I would replace the Univolt at the same time. I'm not footing the bill so, it's really your decision. While you have the fuse list, and are out shopping, get a pack of each of the fuse types in the panel. If you have any question about what you have, take along a sample when you go to the store.

As you are messing around, be careful of 120V wiring. It can kill you. Also be careful of the un-fused sides of the 12V wiring. If a battery is involved, you can smoke wires pretty easily. Been there / done that !!

Plan on this being a fun way to spend the weekend. If you get done early, crack open a beer. Don't rush it.

Bob
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Old 03-15-2018, 07:52 AM   #4
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1978 31' Sovereign
Brooklyn , New York
Join Date: Jul 2017
Posts: 32
Quote:
Originally Posted by uncle_bob View Post
Hi

There are *lots* of ways to go about this. One of the many approaches:

First step is to start documenting what you have. Make some sort of drawing of the fuse panel. Start pulling the fuses and writing down what type and current rating each one is. They may (or may) not be correct. At least you will know what was there.

Next, as noted above, pull all the fuses and do some ohm meter checks. Be aware that some loads read fairly low resistance (A 12 amp DC load may read 1 ohm).

You can pop in a battery for the next step. A power supply is another alternative. If you happen to be able to borrow a current limited / metered supply, it might help a bit. Fuses go in one at a time and only one fuse in the panel at any one time. With the fuse in, see what does or does not come on / work.

Check off devices as you figure out what goes where. Colored dots are one approach. A big master drawing of everything is another approach. Accept that it's a multi pass process. You *will* have to go back a second or third time to find every last thing. If you have a metered supply, note what each circuit is pulling as you check it. A lightbulb tester is usually the fastest way to check what wire is or is not hot .....

Take a look at the dates on the batteries. If they are over 6 years old, replace them. I would replace the Univolt at the same time. I'm not footing the bill so, it's really your decision. While you have the fuse list, and are out shopping, get a pack of each of the fuse types in the panel. If you have any question about what you have, take along a sample when you go to the store.

As you are messing around, be careful of 120V wiring. It can kill you. Also be careful of the un-fused sides of the 12V wiring. If a battery is involved, you can smoke wires pretty easily. Been there / done that !!

Plan on this being a fun way to spend the weekend. If you get done early, crack open a beer. Don't rush it.

Bob
Thanks Bob, I definitely want to replace the univolt, and I was also thinking about replacing the fusebox with a more modern fusebox one that takes automotive fuses. Any thoughts on the type of fusebox? should I be testing the DC wires before I replace the fusebox, or after? I'm also thinking of getting a battery shutoff switch just to make sure I can switch the batteries off.
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Old 03-16-2018, 08:41 AM   #5
Half a Rivet Short
 
2017 30' Classic
Carlisle , Pennsylvania
Join Date: May 2017
Posts: 9,110
Hi

Always check what you have *before* you start doing this and that. Take some careful notes on what does and does not work in the current configuration. It can save a *lot* of time later on.

As with any upgrade / re-do / rework on an AS, what parts to use are very much up to you. One path to follow is to look at what AS used over the years. Most of it is still available. There are a near infinite number of other alternatives. I would lean towards something that uses the "modern" auto fuses. That's just me and there are strong arguments in favor of breakers.

Bob
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Old 03-18-2018, 12:39 AM   #6
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2007 22' International CCD
Corona , California
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Where to start with the 12V electrical system

Manually resettable breakers, aircraft or marine type would be safest...just sayin, if you go for breakers over ATO blade-type fuses that are readily available darn near everywhere.
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Old 03-18-2018, 10:21 PM   #7
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Quote:
Originally Posted by estock View Post
I have a 78 Sovereign 31, I purchased it without any information about the electric system. It seems to have the old style converter, and the glass cylindrical fuses. i want to start testing out the 12v electrical system, and I'm trying to figure out where to start. Do I just hook up a battery and see which fuses blow? Perhaps put a continuity tester on the wires? Really have no idea how to start testing the electrical system.
What progress have you made?
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