What is this wire???

[jrat]

Hello all. I have a parallax converter in my trailer and have a question. I understand the black and red wire coming from the battery. On the same lug as the black wire is a smaller white wire. What is that from? Also, between the red and black lugs is a blue wire labelled only as VCC. The manual doesn't identify this wire. What is it? I ask because I was poking around checking my fuses and noticed the first inch of this blue wire was charred like it heated up too much. My 12V system works fine. My 120 all works when on shore power or geny. The only potential issue is my batteries don't seem to charge well if on shore power. Does this wire charge the batteries? I trimmed and redid the blue wire and have seen no further issue. I unhooked at the battery and while on a geny was getting 3.08 volts between the positive and negative battery cables. Is that too low? thanks,

[wa8yxm]

Colors of wire differ between what electricians use and what electronics types like me use.. And the difference can be as great as black and white

To me (electroinics) and the person who designed your converter BLACK is either negative or chassis ground (Not the same as earth ground)
WHITE, something else

To an electrician WHITE is "Neutral" and bonded to earth ground at some point.. Black is ... Something else (Hot)

So for a white wire to be hooked to the BLACK terminal on the converter... normal.

Now for the blue wire.....

Parallex bought out Magnatek, I know the older 6300 better than I do the 7300 but this I do know

The 6300 had two sets of POSITIVE wires, Red and blue

one went to the battery and to sub circuits like the radio which work best on clean power.. The other just went to sub circuits like lights that do not mind very nasty power (Rectified AC with no filtering) I forget which was which.

But again, if the wiring panel was originally designed for the 6300 or something like it, then both red and blue connect together.

[BFL13]

Just curious, what did you replace it with? Bestconverter has several choices for that.

(Also telling us gives us all a chance to Monday morning quarterback your choice 🙂 )

[jrat]

Thanks all. replaced lower half from BEST Converter - shipped in 2 days! problem solved. I may try to troubleshoot the old one for fun.

[KJINTF]

I would suspect the Parallax converter has gone bad

Suggest you take it out and drill open the cover then take a close look at the two large capacitors and one smaller one hidden under/behind the heat sink. Your symptoms point to this particular failure.

If your handy with a soldering iron and can locate the parts it's not very difficult or expensive to exchange the defective parts.

If you find it defective and do not want to attempt a fix - Please do not toss it in the trash. I would be happy to pay shipping charges to get to here.

[BFL13]

The voltage going up and down suggests a bad contact as you wiggle things so it is 13.8 when in good contact, less when in bad contact. Suspect remains that blue wire repair.

[jrat]

i redid that - only read 4.6v when batts are disconnected and shore power is on. AC works fine but no 12v. I pulled white and blue wire off and read just the wired - mostly 4.6 but sometimes 13 and sometimes 2 ish. Thinking the bottom half of converter is screwed? Why the up and down readings?

[BFL13]

jrat wrote:
OK - the two 30 amp fuses are fine. The blue wire was singed so i trimmed it back and reattached it. How can I test to see if the panel is working? My rig runs fine off the battery bank. Should I disconnect batteries and plug in to shore power and test across the blue and white wire? That should ready 13.8? Is that right?

Correct. Don't use the battery disconnect switch, take the neg or pos wires right off the battery post so you have no battery at all.
Plug in to shore power or generator so you have 120v. You should have 13.8v approx. at the battery lugs on the fuse panel.

If not, (zero volts or whatever) then go back and recheck your blue wire repair, since the last thing that got fiddled with is usually the first suspect 🙂

BTW that burnt blue wire may have come in contact with the white ground at some point--and note that the entire metal box all that comes in is a "live" ground so it can touch almost anywhere for that to happen.

[newman_fulltime]

the blue vcc wire is your converter output wire

[jrat]

OK - the two 30 amp fuses are fine. The blue wire was singed so i trimmed it back and reattached it. How can I test to see if the panel is working? My rig runs fine off the battery bank. Should I disconnect batteries and plug in to shore power and test across the blue and white wire? That should ready 13.8? Is that right?

[BFL13]

jrat wrote:
Hello all. I have a parallax converter in my trailer and have a question. I understand the black and red wire coming from the battery. On the same lug as the black wire is a smaller white wire. What is that from? Also, between the red and black lugs is a blue wire labelled only as VCC. The manual doesn't identify this wire. What is it? I ask because I was poking around checking my fuses and noticed the first inch of this blue wire was charred like it heated up too much. My 12V system works fine. My 120 all works when on shore power or geny. The only potential issue is my batteries don't seem to charge well if on shore power. Does this wire charge the batteries? I trimmed and redid the blue wire and have seen no further issue. I unhooked at the battery and while on a geny was getting 3.08 volts between the positive and negative battery cables. Is that too low? thanks,

The 12v systems are powered by either Parallax converter (13.8v) or battery (12.7v or below) from those pos and neg lugs on the DC fuse panel. The blue converter wire is on the lug with the red battery wire and the white converter wire is on the neg battery lug with the neg battery wire (white or black depending if the pos is red or black---never mind!!!! 🙂 )

When the converter is on getting 120v from gen or shore power, its 13.8v will run the rig plus charge the 12v battery using that 1v voltage spread to get some amps. (this is slow going , you really want to charge a 12v batt at 14.x volts to get a good spread and more amps)

With batt disconnected the voltage at those lugs with converter on should be 13.8v. With batts connected and batts low, the voltage seen at the battery posts would be somewhat less than 13.8, due to current flowing on the wire (called voltage drop) voltage rising as the batts get more full (less current, less voltage drop).

If that 3.08 is not a typo for 13.8, then check the two 30 amp fuses on that same DC dist panel the lugs are on--those are reverse polarity fuses that blow if you wire the battery backwards. If the battery is wired backwards (reversed) your 12v stuff will work except the fans will go the wrong way around, but the converter will not work.

[2oldman]

jrat wrote:
I unhooked at the battery and while on a geny was getting 3.08 volts between the positive and negative battery cables. Is that too low? thanks,

Yeah, about 10v too low!

I looked up VCC, but I don't yet know what that is. And, to have a wire between the + and - terminals (assuming those are hot) is a short circuit. Mabye someone else knows about this.