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Old 08-14-2015, 12:56 PM   #1
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Univolt replacement with PD9245C

Over the past few weeks, I've been traveling up to my Airstream and doing a number of small projects on the trailer, trying to get familiar with its systems and components. One of the issues is the 120v shore power is working OK, but the 12v systems are not working.

I've decided to replace the existing Univolt (with integrated fuse panel) with a new PD9245C and a separate fuse box. I have a question about one of the wires attached to the Univolt. There is a yellow wire coming from the upper left (according to the service manual, this is the Car battery (pos) / Circuit #5 terminal) which is going to a circuit breaker on top of the Univolt. Any ideas what that wire is used for and where it should it be connected on the PD9245C? Picture attached.

Right now, the Univolt is mounted to the floor in the bathroom closet. This seems like a less than ideal location for an electrical box... My plan is to install the new converter in the same closet space but move it up above the shelf so its easier to access.

I'm not at the trailer for another week or so, so I'm trying to plan out all the steps I need to take before I make the trip up North to work on it!

thanks

Alex
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Old 09-01-2015, 06:47 PM   #2
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Finally got around to (starting to) replace the Univolt this weekend! Wow. You really need to be a contortionist to work on this thing at the bottom of the tiny bathroom closet. To make things easier, I removed the shelf above the univolt, by unscrewing it from the side wall, and drilling out three rivets that were holding it in place.

As I got a closer look at the 12 volt wires coming from the univolt, I noticed that the CKT#2 (Yellow) was cut, and no wire was attached to that circuit. The screw terminal for that circuit was completely rusted and frozen. That may explain why someone connected the yellow wire to CKT#5 along with the blue wire (done way before my time). Still not sure about the large circuit breaker attached to the yellow wire.

My plan was to initially remove the nuts that were holding the Univolt to the floor. However, the nuts spin freely, as do the bolts they are attached to, and I couldn't figure out a way to remove them. The bolts appear to come up through the subfloor into the the mounting holes on the unit. Anyone else run into this issue? Any ideas on how to get the univolt out, short of opening up the belly pan to get to the underside of the subfloor?

For now, I decided to leave the univolt in place, and just cut the wires going/coming from it. I wired up a 120v outlet receptacle box with the romex that was previously wired into the univolt. That seems to work fine.

Ran out of daylight today to finish, but will take another stab at finishing it up tomorrow. I'd like to put the new converter and receptacle on the shelf a little higher up, and get everything off of the floor. I am thinking about mounting everything onto a piece of 3/4" plywood.
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Old 09-01-2015, 07:21 PM   #3
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On the univolt the second fuse down looks empty, maybe they moved the yellow circuit from there because the terminal on the fuse had problems and wired it through a breaker to the positive post? What is the labeling next to that fuse slot?
Yellow being from tv charge line not likely, unless it's a Canadian spec trailer. It's probably the house yellow circuit. The blue wire is probably the tv charge line.
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Old 09-01-2015, 08:09 PM   #4
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HiJoe - thanks - Trailer is not Canadian spec. The labeling on that one (in the upper left corner) is (CKT#5 & Charge).

Any idea why there would be a circuit breaker in the middle of the yellow wire? I don't see any circuit breakers on the other 12v wires...
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Old 09-01-2015, 09:55 PM   #5
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What fuse panel are you using?
The other positive wires go through the fuses on the end of the univolt. Fuses doing what fuses do. The yellow one is wired directly to the positive terminal , so to protect the circuit they wired in a 12v breaker in place of a fuse. Might have been easier for the person who did it than finding an inline fuse to put in the circuit. Or they possibly kept popping fuses on the circuit so put in a breaker. I hate those 12v circuit breakers, they auto reset so there could be a problem and it could "trip" but then reset, repeat over and over, leading to some serious damage.
Since it's a positive load or supply you can simply attach it to the positive bus on your new fuse block with an appropriately sized fuse to replace the breaker. Electricity doesn't care which way it flows so a positive connection feeding into or out of the positive bus is completely transparent to the electricity.
You'll only see fuses or breakers on the positive wires.
The yellow wire won't connect to the pd9245(PD). The only connections on the pd are the 120v supply plug, a positive and negative. The positive and negatives from the pd get connected to the fuse panel appropriate busses. All the other wires from the univolt get connected to the appropriate busses on the new fuse panel with appropriate fuses on the positive wires.
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Old 09-01-2015, 10:07 PM   #6
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Here are some other threads I've helped people on same topic with. You don't have to read them but they might help a little.

http://www.airforums.com/forums/f37/...er-136407.html

http://www.airforums.com/forums/f37/...ck-135473.html

http://www.airforums.com/forums/f219...er-133233.html
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Old 09-02-2015, 11:03 PM   #7
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Fuse box

I will be using the fuse box from Vintage Trailer Supply (picture attached). I won't get a chance to hook it up for another week or so. Will post an update after I get it all connected.

thanks for your help.
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Old 09-09-2015, 03:29 PM   #8
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Getting Ready to connect new converter

Well, after some wrestling with the old Univolt, I managed to get it out of the bathroom closet - man, that thing is heavy! Found significant floor rot once I got the univolt out. That will be a project for another day.

I am using the attached schematics as a reference on connecting the converter and the fuse box.

I have a couple questions about the wiring of the new PD9245c converter:

- Which of the wires going into the univolt was the "Chassis Bonding" wire? Would that be the heavy white wire that was connected to the "Load-White" terminal?

I assume the univolt had to have a chassis bonding connection in order to work properly... If not, do I need to attach a new wire somewhere on the Airstream frame?

- Also, maybe I missed it, but I didn't see any ground wire coming from the negative terminal of the trailer battery as shown in this schematic. All I see is the single negative lead going to the univolt "Trailer Batt-Black" terminal. Is another ground wire needed here, and if so where should it be connected?

Thanks for any suggestions.

-Alex

p.s. Other than a boat anchor, is there any value in the old Univolt? Museum piece maybe?
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Old 09-10-2015, 07:11 PM   #9
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The battery and negative from the converter don't need to be separately grounded. You just need to have a negative ground on the negative side of the system somewhere. Generally running a wire from the negative side of the fuse panel is used and attached to the frame or skin somewhere. There should have been a heavy white wire that filled this function in the system originally.
The ground lug just needs to be grounded to the shell. Attach a wire to the lug and crimp a ring terminal on the other end and screw it to the shell. The converter will work without it but it's a safety measure in case there was an electrical problem inside the converter that charged the metal converter shell. It will dissipate that voltage to the shell instead of a person touching the converter.
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Old 09-10-2015, 07:38 PM   #10
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Don't forget the circuit breaker or fuse on the positive from the battery. I recommend staying away from the kind pictured as they are auto resetting. This means that if there is a fault, the high current causes a metal strip in those breakers to get hot and flex away from the contact, once it cools down it automatically reconnects itself to the internal contact, sending voltage back to whatever the problem is, repeat..... Not an ideal situation!
I recommend a resettable breaker similar to the one here;
http://www.amazon.com/gp/aw/d/B0024J...F1L&ref=plSrch
Plus it lets you manually open the breaker to disconnect the battery without having to disconnect the battery terminal at the battery.
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Old 09-10-2015, 09:27 PM   #11
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New converter up and running!

HiJoe - Thanks for the help. I actually got everything working earlier today.

I built a new shelf as the old one was in bad shape, and I wanted to put the converter up off the floor. It was pretty cool when I plugged it in, and all the 12v lights (even the door light) and fan in the bathroom came on - probably the first time in 10 years that they have been on!!

Attached picture shows the setup. I did run a bare 8 ga copper wire to the shell from the side grounding terminal on the converter. Also, as you noted, the heavy white wire I connected to the "ground terminal bus" on the fuse panel - I actually neglected to connect this wire initially, and was scratching my head for a few minutes wondering why nothing was working...

I don't currently have a battery, so don't need to worry about that yet, but will look into the circuit breaker that you recommended.

I also don't have a car hookup to the trailer, so I didn't connect the heavy blue wire to the fuse panel. The old univolt/fuse panel had the Car Battery and Circuit #5 on the same terminal/40 amp fuse. From looking at the 12V wiring schematic for the 1972 Safari (attached), I don't see what else if anything Circuit #5 is used for - except possibly the Radio (which I have disconnected at present - not even sure if it still works).

Also, wondering if I should switch the Inteli-Power unit to "Storage" mode from "Normal" mode since I don't have a battery attached. Appreciate any insights into this.

thanks again for your help.

-alex
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Old 09-10-2015, 10:25 PM   #12
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They had the blue charging line and circuit 5 on the same fuse due to the lack of available fuse space, simple as that. Not because of anything special on circuit 5. My blue house circuit fed my radio , end cap lights, tv antenna amp, and a 12v socket outlet. Not much. If you followed on the diagram you should have a good idea of what's on yours. Since you have the fuse space you should have the charge line and ckt 5 on separate fuses for simplicity. Ckt 5 should use a 20a fuse.
Since you don't have a battery in the loop the normal/storage won't make a difference. It changes how the unit charges the battery to prevent damage from overcharging while in storage.

Glad everything is working. Good job!
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Old 09-11-2015, 06:10 PM   #13
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After looking at things more closely, the blue (40A) charging wire is the only wire remaining unconnected. I guess that means there is no 20A "circuit #5" in this trailer...

Also, on an unrelated note:

I tripped one of the 120v circuit breakers this morning (hot water kettle & electric heater on at same time). I thought (incorrectly), that one of the circuit breakers was for all of the 120v outlets, and the other circuit breaker was for the Converter/Charger. However, the converter was also shutdown when the breaker tripped.

I can't figure out what the other circuit breaker controls. Any ideas?

thanks
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Old 09-12-2015, 10:42 AM   #14
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Just looked at the 120v wiring diagram - 1 circuit is for the A/C unit, and the other circuit is for everything else in the trailer.
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