Upgrading 1972 Univolt to Boondocker and searching for diagrams or pictures for insta

[action95]

Hello all, I am renovating a 1972 Overlander and in the process of upgrading the old Univolt converter for a new Boondocker 1200 series converter and blade fuse box. Does anyone have experience with this that can send a diagram or picture of how the old wires will be hooked up to the new converter and fuse box? Thanks for any help I can get.

[dbj216]

Hi and welcome to Air Forums. You are wise to update to a modern converter. Converters are relatively easy to install. However, in my 75 Overlander, Airstream decided to install the converter behind the bathtub.
Great. Makes the job much harder.

Our Airstreams are "univolt" and that is 12vDC. The power supply for the 12vDC is your battery OR your converter if you are plugged into shore power. So there are two wires coming from the converter just like there are two wires (red plus and black minus) from the battery. I might add there is an additional blue wire called "car charge" wire that charges the battery from the tow vehcile alternator when we are towing the trailer.

There are typically 3 12vDC circuits running in the walls of our trailers. Some newer trailers have 4 circuits. Each of the circuits are protected with a fuse or circuit breaker. Take pictures and label each wire in the current fuse panel. Learn what each wire does. Note your fuse panel has a "bus bar" to collect all three circuit ground wires. And there will be a 12vDC ground wire to the frame of your trailer. Then transfer a wire at a time to the new fuse panel.

The converter is easy to install, the fuse panel has more wires. But you can do it.

David

[action95]

Thank you very much for your reply. It was very helpful. Do you have any insight on how I would take the picture of the fuse box you showed transfer it to a blade fuse box like the one pictured here?

[TG Twinkie]

The large red and the smaller blue wires go to the positive buss bar connectors.
The large black wire goes to the ground buss bar.
The large white wire goes to the ground buss bar.
The 4 different colored wires go to the terminals on the right in the pic
It doesn't matter which one goes where. Just make sure the fuse sizes are the same as the old. The circuits on the old unit are numbered 1-4 so connect the colored wires to the same numbers on the new unit.
The large flat copper bar at the bottom is a shunt. If you want the meter to work you will need to remove it from the old univolt and mount it on an insulated surface.
When you get that done move the wires from the ground buss. Then connect all 4 (2 large, 2 small) just as they were on the old unit.

[dbj216]

TG Twinkie hit the nail on the head. He gave a good explanation of the different wires in the 12v circuit of our trailers. It is important that you likewise identify each wire function.

David

[bwhitaker]

Hi there. I would like to add to this. I think I've done the same thing as action95. I took out the univolt in my '71 and put in the 9100 converter and the same fusebox they pictured. On the DC positives, I attached one from the battery, one from the converter, and one from the car charge. My problem is it doesn't work. When my battery is charged, the interior electric works. When I plug the trailer in, the converter turns on (I can hear the fan) but it does not charge the battery. When I remove the battery (or it dies) then I still get no interior power even if I'm plugged into land. When I say interior power, the 120 V receptacles do work, just none of the 12 V lights and what-not. What am I missing? Thank you in advance.

[TG Twinkie]

Sounds like you are missing a common/ground wire between the ground buss and the battery.
If the lights work with the converter powered. That sounds right.
Measure the voltage between the + terminal of the battery and the chassis or skin of the coach.
Measure between the terminals of the battery.
All with the converter off.

[bwhitaker]

unfortunately the lights don't work with the converter powered...

[bwhitaker]

So I checked, and there is power coming from the battery wire, the converter wire, and the car power wire. I use a small 12v powermeter that you alligator clip to the ground and the light turns on. I clipped it to the ground that I installed to the AS frame and nothing. I clipped it to a SS rod I stuck in the ground and the powermeter light came on. I'm guessing the grounding to the frame is the culprit? The frame is very rusted. Thoughts on a place to ground everything?

[kenfconnor]

Originally Posted by bwhitaker

So I checked, and there is power coming from the battery wire, the converter wire, and the car power wire. I use a small 12v powermeter that you alligator clip to the ground and the light turns on. I clipped it to the ground that I installed to the AS frame and nothing. I clipped it to a SS rod I stuck in the ground and the powermeter light came on. I'm guessing the grounding to the frame is the culprit? The frame is very rusted. Thoughts on a place to ground everything?

I am no expert but I think you could just ground the 12v directly to the interior skin with a screw.

[TG Twinkie]

We are really getting off into the weeds here.
Are you saying that earth ground is completing the circuit(s) in your coach?
By that I mean if you pull the ground rod out of the ground the lights go out.
The white wire in the post #2 should be connected electrical to a clean spot on the frame. Black goes to the battery - post. The black and white wires should be connected to the ground buss if you are not using the shunt. If you are using the shunt it must be mounted on an insulating material isolated from any metal. And wired as it is in post 2. In other words the shunt needs to be in series between the ground buss and the battery - terminal.
Obviously the negative battery lead is connected to the frame otherwise nothing would work.
Run a wire from the ground buss on the DC panel directly to the negative post of the battery. If you have the negative wire from the converter connected to the DC ground buss this should complete the circuit.
Then all you have to do is figure out where the negative side of that portion of is not connected. Refer to the pic in post #2. I think you are missing either the large black wire on the left side of the shunt. Or the white wire on the right side of the shunt.
When you connect the Wire I mention first you should see the voltage at the output of the converter standing at the battery. Say 13.6 volts or so.
If you don't have a multi meter. You need one for this kind of trouble shooting.

[Bill M.]

I am a wimp. I looked at mine and the fuse box and the new panel and I decided that the converter was the only thing that was giving me problems. So I just left the fuse panel and put in the new converter. I have replaced one fuse in 12 years when one of the 12 volt outlets shorted to the skin. Just the converter is a fairly fast and easy switch.

[TG Twinkie]

Did you get things to work?

[kenfconnor]

Originally Posted by Bill M.

I am a wimp. I looked at mine and the fuse box and the new panel and I decided that the converter was the only thing that was giving me problems. So I just left the fuse panel and put in the new converter. I have replaced one fuse in 12 years when one of the 12 volt outlets shorted to the skin. Just the converter is a fairly fast and easy switch.

That is a good decision. I did the same for one of my trailers. I dont see any reason to replace a perfectly good fuse panel. On my 81 the old converter weighed over 30 pounds and put off a ton of heat. Upgrading it offset much of the weight of adding a second battery and provided 4 stage charging. Added a 4 position battery switch (bat 1, bat 2, both, off). I did add a digital volt/current/watt meter which provides a lot of useful info. Cheap at under $20 off Amazon. Better to spend the time to add real improvements vs the fuse panel.

[bwhitaker]

Well to make a long story short, everything is working now. Finally broke down and bought a multimeter...amazing what technology can do these days. Anyhow, i was getting volts from the converter + line but not when I put the - on the converter - line. Turns out in haste when i inserted the wires, I forgot to strip the - before tightening it down. User error yet again to blame. Thanks for all your help!