12 volt circuits dead when on hookup...

Hi,

I have an R-Vision Trail-lite 2002 with a Parallax 7355 converter.

My rig is currently on mains hookup but none of the 12v circuits are working.

Using a multimeter I have discovered the following:

Removing both 30amp polarity fuses and testing between the converter input to the fuse board (blue wire) and the negative connection gives 13.6 volt.
Testing across the battery connections at the converter fuse board gives 13.6 volt
Replacing the polarity fuses and testing from any of the 12v circuits positve (just below fuse) and the battery negative connection on the fuse board gives 13.6v.

NO 12v circuit works.

Now, despite having a reading across the battery connections on the converter fuse board of 13.6 volt, the actual reading at the battery is 9 volt.  Now I know that this means that the battery is no good, I can't understand why I get the differnce in readings.

Also, and perhaps crucially, if I connect an external battery charger to the battery then the 12v circuits in the coach come on...

And in case it helps, with the polarity fuses removed, the reading at the fuse board across the battery connections is the same as at the batteries.

I am really confused as all the information I can find says that the Parallax should be powering the lights etc even if there is no battery, and I do read 13.6 volt at the 12v circuit fuse bu tget no power anywhere.

I really hope you can help as we are due to go away for a couple of weeks real soon.

Bryan

What happens if you completely disconnect the battery?

If it requires a new battery, why not put it in?  Now.......

Thanks for the reply 

Without a battery I still have no lights etc.  But the Parallax 7355 converter should be powering the 12v stuff without a battery anyway.

Not concerned about the battery, that's an easy fix.  But I do need to get the 12v stuff running off the hookup.

I've dug deeper and the converter is getting 110v from the hookup, and it is giving out 13.7 volts to the fuse board.  And the fuse board is putting 13.7 volts through the fuses to the live wires for the circuits  ???

I am sooooo confused  :'(

Have you checked the circuit brakers? I had a similar problem not too long ago where while connected to shore, the converter was not charging the batteries and I was getting low readings at the points you just mentioned. I removed all the fuses, cleaned the connections, also at the fuse board, then I replaced the adapter (30amp to 15amp) cause it looked melted on the hot wire. After done all that, I put back all the fuses (including the 30amp fuses), and my batteries charged up back to 12v and the readings were correct again. I don't know if it was the cleaning or the changing of the adapter but it worked. Also I heard on another forum that there is a possibility that the battery isolator switch may be at fault.

Bryan said:

Also, and perhaps crucially, if I connect an external battery charger to the battery then the 12v circuits in the coach come on...

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Don't you think a GOOD 12v battery hooked up as you have the battery charger would do the same thing?

aka Porky said:

Don't you think a GOOD 12v battery hooked up as you have the battery charger would do the same thing?

Click to expand...

Possibly, but the parallax should power the 12v circuits even if a battery is not present.

Bryan said:

Possibly, but the parallax should power the 12v circuits even if a battery is not present.

Click to expand...

That's the third time you have said that.  Is it doing it yet?

aka Porky said:

That's the third time you have said that.  Is it doing it yet?

Click to expand...

Sorry if I am repeating myself, but I am only doing so to clarify that the battery is not what is concerning me at the moment.

Fred G. said:

Have you checked the circuit brakers? I had a similar problem not too long ago where while connected to shore, the converter was not charging the batteries and I was getting low readings at the points you just mentioned. I removed all the fuses, cleaned the connections, also at the fuse board, then I replaced the adapter (30amp to 15amp) cause it looked melted on the hot wire. After done all that, I put back all the fuses (including the 30amp fuses), and my batteries charged up back to 12v and the readings were correct again. I don't know if it was the cleaning or the changing of the adapter but it worked. Also I heard on another forum that there is a possibility that the battery isolator switch may be at fault.

Click to expand...

Which circuit breakers?

I'm not too concerned about the battery charging, I'm sure that once the main issue is sorted the replacement battery will charge okay.

Which adapter did you replace?

Battery isolator is okay I think.  When I have a battery connected the isolator switch just inside entry door does what it should.



There is something else a little odd...

Further diags - I have removed the front of the parallax; the converter is getting 110v, the fuseboard is getting 13.6v from the converter.  I removed the positive lead from the fuseboard (that is connected to the battery, allegedly) and whilst the battery has a seperate charger attached , the wire reads 16-ish volts even though the battery that is at the other end reads 9 volts...

I mention this in case it is helpful - I repeat, I'm not too concerned about the battery, the parallax should power the 12v on it's own and that is what I need to fix first  

Follow these troubleshooting procedures to determine if your converter is bad or not.
http://www.parallaxpower.com/7300/Flowchart7300.pdf
If everything check out OK, then you need to trace back the 12v circuit.

Does your rig perhaps have a battery disconnect switch that is off? Most motorhomes have them, but only some trailers do.

The battery disconnect switch is intended to isolate the RV's 12v electrical system from the battery and in some designs it also isolates it from the converter.

Fred G. said:

Follow these troubleshooting procedures to determine if your converter is bad or not.
http://www.parallaxpower.com/7300/Flowchart7300.pdf
If everything check out OK, then you need to trace back the 12v circuit.

Click to expand...

Already done that    result is that cxonverter is working fine.

Trace which 12v circuit?  The battery is not included remember and the 12v circuits in question are the lights etc...they can't allbe wrong and besides, if I bring the battery back into play it powers the lights etc.

RV Roamer said:

Does your rig perhaps have a battery disconnect switch that is off? Most motorhomes have them, but only some trailers do.

The battery disconnect switch is intended to isolate the RV's 12v electrical system from the battery and in some designs it also isolates it from the converter.

Click to expand...

Yes it does, and as it is 12volt powered from the battery it works as follows:
Battery connected - switch works fine, on/charge/use, everything fine - switch off/store all 12v disconnected (no lights etc.)
Battery disconnected - all 12v dead anyway as parallax not providing power to 12v circuits.


BTW Thanks for all the advice and help guys 

This sure is a mystery. As I recall the 7355 wiring, it has only one 12v output that does both charging and provides house 12v power. Older Magnetec 63xx series had separate outputs for charging and house power, but I don't think the 73xx series is designed that way. I believe the 73xx 12v output goes to the 12v bus in the power center and then to both batteries and house 12v system. Perhaps you can verify that is how it is wired?

Given that, it would seem to be impossible for it to do what you describe, unless the converter simply shuts down when it finds no battery load.  The bad house battery may be having some odd effect on the whole situation. I'd replace that and see how/if the symrtoms change.

RV Roamer said:

This sure is a mystery. As I recall the 7355 wiring, it has only one 12v output that does both charging and provides house 12v power. Older Magnetec 63xx series had separate outputs for charging and house power, but I don't think the 73xx series is designed that way. I believe the 73xx 12v output goes to the 12v bus in the power center and then to both batteries and house 12v system. Perhaps you can verify that is how it is wired?

Given that, it would seem to be impossible for it to do what you describe, unless the converter simply shuts down when it finds no battery load.   The bad house battery may be having some odd effect on the whole situation. I'd replace that and see how/if the symrtoms change.

Click to expand...

Spot on Gary.  One 12v from converter to fuse board where the 12v loads are - the battery is seen as just another load.  This is confirmed by the parallax website info.

Impossible?  I know!  That's why I am soooo confused  ???

I have tried disconnecting the battery positive wire at the fuseboard but I will remove it completely and see if anything changes, and then add a good battery and see what happens.


One extra thing - it has been suggested to me that there may be a thermal cutout somewhere with a little reset button on it but it could be anywhere...Can any-one shed any light on this possible solution?

According to Parallax schematics, your converter should have two 12v outputs. The white wire goes to terminal C (I believe) which charges the batteries. The blue wire goes to terminal D (or viceversa) which supplies 12v to the coach for lights and everything else. If you say that when connected to shore power, you have 13.7v at the blue wire, then check for volatge after every 15amp fuse (I believe 5 or 6 depending on how many devices you have). If in fact you can read 12v after the fuses, then the next thing is to check for rats behind the converter panel. I doubt that they would chew every 12v wire available, but it is possible. They have eaten whole trunks of fiber optic cabling at my workplace. If you cannot read any voltage after the fuses, then you might have a loose contact between the blue wire terminal and the fuse terminals at the fuse board.

All the material I can find would indicate that Fred is correct.  I would check every wire and every connection on the DC distribution side of that converter. 

I'm not sure if Parallax uses the same method of isolating the regulated DC output from the charger output that the older Magnetek converters did, or not.  Seems to me that that was a relay.

Thanks Fred and Lou,

Yes there are a blue wire and a white wire coming from the converter to the fuse board.  The blue is the +ve and the white (I am pretty sure)  is the -ve.  The blue is connected at the top of the board in the centre and the white is connected behind the board to the same post that the battery -ve connects to on the front.

I can read 13.6 volt after the fuses.

I don't think the wires are chewed.  To support this, when I connect a battery to the board the 12v circuits work.  Lights come on.  BUT very dim and is is very obvious that the lights are being powerd form the battery, not the converted 12v.

After all your help and support I am starting to think that there may be something else messing it up.  Maybe a relay, maybe a cutout.  I would have thought that a cutout or relay fault would take out the converter and show no volts at the fuses but maybe not.  I just don't know.

I'm still prety sure that there is not a seperate charger circuit and that the battery is just there as another 12v circuit/load attached to the converter.

Bryan, maybe these diagrams will help figure this out.  They are of older Magnetek converters which were the ancesters of the Parallax converters.

here and here

They show you how Magnetek used a relay point to switch the loads from the converter to the battery.  Hope they help

I believe both of those diagrams pertain to the 63xx series of converters, while Bryan has a 73xx.  They MAY still be essentially correct for a 73xx, but we can't be sure.

I can find no reference to a reset switch in the 73xx operator manual, which is available here:

http://www.parallaxpower.com/7300/51092351-000%20rev%20G.pdf

The 73xx Installation manual shows the wiring, which may be instructive:

http://www.parallaxpower.com/7300%20Series%20Installation%20Guidelines%20rev%20A.pdf

It does show reverse polarity protection fuses, which might result in some strange readings if one or both are blown.

There is also a troubleshooting flowchart:

http://www.parallaxpower.com/7300/Flowchart7300.pdf

which shows the proper method for checking converter output power.

RV Roamer said:

I believe both of those diagrams pertain to the 63xx series of converters, while Bryan has a 73xx.  They MAY still be essentially correct for a 73xx, but we can't be sure.

Click to expand...

I thought I made it clear that the diagrams I linked to were the older Magnetek converters. i.e.63XX or prior.  (maybe not)

RV Roamer said:

I can find no reference to a reset switch in the 73xx operator manual.....

Click to expand...

Any reset "button" or "plunger" would probably be located on the circuit breaker (in the positive battery lead) shown on the last page of your diagram(s) link here