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Old 08-24-2016, 10:22 PM   #1
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Replacing an old converter ... what could I have messed-up?

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Originally Posted by elmer View Post
I accidentally shorted out a circuit on my old 1976-era TU-331W UniVolt, and even after replacing the blown fuse, the unit now sounds different and has a nasty 60Hz/30Hz ripple on the output.

So that's the final nudge that I need to replace it with something more modern.

I've bought a PowerMax PM4-45 and a new fuse panel from Amazon (not sure what the difference is between Amazon's standard PM4 and the PM4B "boondocker" that seems to be recommended here, except for the extra year of warranty).
Hmmm ... I miust have done something wrong in the install of the new power converter, because I'm getting some weird results.

I hope someone can give me a clue about what I did wrong.

I installed the new Parallax fuse panel, and installed the PM4, and decided to test everything with the battery disconnected (to avoid problems).

All my 12V lighting works perfectly, and the 120V outlets still work as expected.

The PM4 outputs 14.6V when connected, just as the manual says that it should.

So I disconnect the shore power, and disconnect the PM4 from the fuse panel, and connect the battery.

All my 12V lighting works perfectly, and the 120V outlets are dead, just as you'd expect.

So I disconnect the battery, connect the PM4 to the fuse panel again, and connect the battery ... and there's a spark when I go to connect the 12V to the battery ... something is drawing power!

Anyway no burning smell or anything, so I connect the shore power.

Now none of my 12V lighting works at all!

So I disconnect everything, and repeat the cycle with the same results.

The 12V lights work with either the PM4 by itself, or with the battery by itself ... but not with the fuse panel connected to both at the same time.

The wiring of the fuse panel couldn't have been simpler ... PM4 negative, and Argosy white, and battery black all going to the negative bus on the fuse panel.

PM4 positive and battery red both going to the positive bus on the fuse panel.

Each of the Argosy's branch wires going to different 20A fused +ve connectors on the fuse panel.

The only thing that I didn't do was connect the PM4's ground lug to anything (isn't it grounded by the 120V plug?).

Is that my mistake? Should I connect that to the negative bus on the fuse panel, too?

Or could I have a bad battery or a bad PM4 converter?

I've been charging the battery with an external automotive battery charger every few weeks to keep it topped-up when I'm not using the trailer. That charger seems to indicate that the battery is taking a charge normally.

Can anyone offer any suggestions of how to proceed troubleshooting this?
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Old 08-24-2016, 10:55 PM   #2
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DC ground has nothing to do with AC ground. Not sure if this is the problem but you definitely want everything properly grounded.
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Old 08-24-2016, 11:15 PM   #3
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How big of a spark did the battery cable throw when you hooked it up?

Does your wiring or system incorporate auto reset circuit breakers?

What gets me is that whether or not the new converter is working, (the way you describe the wiring), the battery should light the lights in any case.

The only thing I can think of is that the converter is causing a dead short. A dead short like this would throw a BIG spark if the battery is even close to a fair charge.


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Old 08-24-2016, 11:36 PM   #4
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Originally Posted by bbdo View Post
DC ground has nothing to do with AC ground. Not sure if this is the problem but you definitely want everything properly grounded.
That makes sense ... but what am I going to ground it to?

AFAIK, the skin of the Argosy is the negative of the 12V circuit.

Am I supposed to connect that 12V-negative to the ground of the 12V side of the PM4?

That just didn't "feel" right to me ... so I didn't do it. Perhaps that was a mistake???

Should I try to figure out where the AC ground wire connects on the large breaker box and connect that wire to the PM4's 12V ground lug?

There does seem to be a bare copper wire going from unidentified-point-A to unidentified-point-B in the Argosy's electrical space ... but it certainly wasn't connected to the old Univolt that I replaced.
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Old 08-24-2016, 11:57 PM   #5
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Originally Posted by J. Morgan View Post
How big of a spark did the battery cable throw when you hooked it up?
Not big enough the freak-me-out, or to blow the 50A safety-fuse in the battery's negative line. Maybe a 60th of a second, nothing sustained. More like an equalization of voltages, or the rapid discharge of a capacitor (in my layman's terms).


Quote:
Does your wiring or system incorporate auto reset circuit breakers?
The old 1976 AC breaker box has manual reset circuit breakers.

The new Parallax 12V fuse panel uses standard automotive fuses.

The only other fuse left is the 50A safety fuse on the battery's 12V negative line.


Quote:
What gets me is that whether or not the new converter is working, (the way you describe the wiring), the battery should light the lights in any case.

The only thing I can think of is that the converter is causing a dead short. A dead short like this would throw a BIG spark if the battery is even close to a fair charge.
That would be my understanding of the circuit, too.

Most of my light fixtures should pull approx 18W each (with both fluorescent and LED fixtures), but the LED outside lights should only pull 4-6W (they're new bulbs and I haven't measured them, yet).

None of those fixtures work when both the PM4 and the battery are both connected.

That suggests (to me, in my ignorance), that something in the PM4's output circuitry is effectively shorting the battery ... or at least pulling enough power out of it that the voltage is dropping.

I can't imagine a healthy battery dropping it's voltage by that much without a serious current draw.

But I can't imagine why the PM4's 12V-output would be drawing that much current from the battery without some-fuse-somewhere blowing.

I'll dig out a multimeter tomorrow and take some voltage readings ... but at the moment I'm confused by the situation, and I don't know what the voltage readings could possibly tell me.
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Old 08-25-2016, 06:14 AM   #6
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The ground lug on pm4 must be connected to skin. I don't no if that causes prob. that you are having.
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Old 08-25-2016, 07:09 AM   #7
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Replacing an old converter ... what could I have messed-up?

Do you know how to use a multimeter? If so, do the following.
With the meter set to DC volts.
Connect the black lead of the meter to the Battery black lead. Connect the red lead of the meter to the battery red.
You should read a positive 12-13 volts. I would assume you have made sure the black lead of the battery goes to the negative post and the red goes to the positive post.
We are checking for the correct polarity.
Can you see where the opposite ends of the Argosy black and white are connected?
The white should connect to the skin/frame of the coach and to the negative terminal of the fuse panel.
The black Argosy wire is the question. I am going to take a guess that it is the charge line from the TV. So for now leave it disconnected.
Then hook up the converter to the respective + and - terminals on the fuse panel. Connect the battery.
Let us know what happens.
Pictures of you setup would help.
Have you checked the 2 large fuses on the converter? They are reverse polarity protection devices. If your converter works they will be good.
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Old 08-25-2016, 10:39 AM   #8
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Quote:
Originally Posted by TG Twinkie View Post
Do you know how to use a multimeter?
I can't remember where I put mine, I'll borrow one from a friend and post the results later.

Quote:
If so, Pictures of you setup would help.
Here's the fuse panel ...

The -ve bus is on the left.

Left Top is the battery -ve.
Left Middle is the Argosy skin -ve.
Left Bottom is the PM4 -ve.

The +ve bus is on the top.

Top Middle is the PM4 +ve.
Top Right is the battery +ve.

The fused +12V circuits are on the bottom.

Bottom 1,2,3 are the Argosy's 3 12V lighting lines.
Bottom 5 is the Tow Vehicle 12V.

The black spots on the old wires is discoloration from proximity to the original old Univolt. It is surface-only and doesn't go deep into the insulation.





Here's the PM4 ...

Note that the PM4's output ground lug is currently disconnected.




Here's the wires coming from the battery box and the large 50A safety fuse ...

On the left, you can see the large copper ground wire that goes to the 120V breaker panel that's in the closet above this picture.

The PM4 120V power plug is what's plugged into the outlet in the center of the frame.




Here's the floor behind the fuse panel and the mess of wiring for context of the layout ...

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Old 08-25-2016, 03:40 PM   #9
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I can't remember where I put mine, I'll borrow one from a friend and post the results later.
The battery registers 12.5V when it's disconnected and on the garage floor.

I took it to my friendly local independent auto shop that's been doing my truck servicing for years and they put the battery on their battery tester.

It registers in great condition, with 605 CCA ... that's for a 3 year old type 13 marine/rv battery with a rating of 85AH and 550CCA.

This morning the PM4 (that had been connected all night) was outputting 12.9V into the Argosy's fuse panel, which I guess makes sense for it trying to ramp down the charge on the battery that it thinks is connected (even though it isn't really).

At this point, the only thing that I can think of the problem being is the missing ground connection on the PM4, even though I can't figure out *why* that would be a problem.
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Old 08-25-2016, 04:55 PM   #10
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The earth ground connection has nothing to do with the converter output.
I see the wire which is connected to the fuse on the wall. Where does each end of it connect? Typically the fuse is inline with the negative battery lead. I see it loops up but can't see if it is connected to anything other than the fuse on the wall.
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Old 08-25-2016, 05:41 PM   #11
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Quote:
Originally Posted by elmer View Post
Hmmm ... I miust have done something wrong in the install of the new power converter, because I'm getting some weird results.

I hope someone can give me a clue about what I did wrong.

I installed the new Parallax fuse panel, and installed the PM4, and decided to test everything with the battery disconnected (to avoid problems).

All my 12V lighting works perfectly, and the 120V outlets still work as expected.

The PM4 outputs 14.6V when connected, just as the manual says that it should.

So I disconnect the shore power, and disconnect the PM4 from the fuse panel, and connect the battery.

All my 12V lighting works perfectly, and the 120V outlets are dead, just as you'd expect.

So I disconnect the battery, connect the PM4 to the fuse panel again, and connect the battery ... and there's a spark when I go to connect the 12V to the battery ... something is drawing power!

Anyway no burning smell or anything, so I connect the shore power.

Now none of my 12V lighting works at all!

So I disconnect everything, and repeat the cycle with the same results.

The 12V lights work with either the PM4 by itself, or with the battery by itself ... but not with the fuse panel connected to both at the same time.

The wiring of the fuse panel couldn't have been simpler ... PM4 negative, and Argosy white, and battery black all going to the negative bus on the fuse panel.

PM4 positive and battery red both going to the positive bus on the fuse panel.

Each of the Argosy's branch wires going to different 20A fused +ve connectors on the fuse panel.

The only thing that I didn't do was connect the PM4's ground lug to anything (isn't it grounded by the 120V plug?).

Is that my mistake? Should I connect that to the negative bus on the fuse panel, too?

Or could I have a bad battery or a bad PM4 converter?

I've been charging the battery with an external automotive battery charger every few weeks to keep it topped-up when I'm not using the trailer. That charger seems to indicate that the battery is taking a charge normally.

Can anyone offer any suggestions of how to proceed troubleshooting this?
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I know its too late now for photos, but in the future, use your small camera and take photos from every angle before unhooking. Its good to use tape and write on the end of wires, as you disconnect them, where they were originally attached, and take a photo. Tedious, I know, but I have learned the hard way. I put a new power converter in my 1990 Excella, replacing the ancient one that cooked batteries. First I labeled things (I'm older and I know I will forget in a matter of hours!) and took photos. Unhooked the univolt. Next day, hooked up the new unit and thought I remembered how things went, and everything had a connection. No loose wires. Hooked up to power, but hadn't thrown the breaker switch on yet. Something just made me nervous. Got out the photos, studied them. Quickly unhooked several wires and reconnected differently. Powered up the system and it worked perfectly. I loose sleep wondering what would have happened if I had powered it up before rechecking my photos. Best of luck getting yours safely and properly connected.
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Old 08-25-2016, 06:21 PM   #12
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Quote:
Originally Posted by TG Twinkie View Post
I see the wire which is connected to the fuse on the wall. Where does each end of it connect? Typically the fuse is inline with the negative battery lead. I see it loops up but can't see if it is connected to anything other than the fuse on the wall.
It's just a *long* piece of thick wire that loops around and is attached to the wall (no electrical connection) to provide strain relief.

It just goes battery-negative-post to 50A fuse to the new fuse-panel's -ve bus, so it's wired exactly as you describe.
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Old 08-25-2016, 08:48 PM   #13
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I know its too late now for photos, but in the future, use your small camera and take photos from every angle before unhooking.
Do you mean something like these?

Old TU-331W power converter DC connections ...

The 3 on the left are marked "branch circuits", the 4th is marked "Tow Vehicle", and then you've got the battery +ve, and the battery -ve which is on the same physical connection as the white Argosy skin -ve.




Old TU-331W power converter AC connections ...



As far as I can see, I've matched the connections with the new fuse panel and PM4.

Perhaps someone here can see something that I missed.
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Old 08-25-2016, 09:41 PM   #14
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There's quite a bit more than that extra year warranty
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