Visit our Popular Forums

4RXLA · 06-19-2010, 12:12 AM

I recently had my old univolt replaced with a modern converter that won't fry my batteries. Before replacing the univolt, the red "power on" light on the control panel worked. Now the light does not work but the converter is working fine. I checked the wiring from the 12V panel to the converter and there is a brown wire coming out of the 4 amp "power on" fuse that is taped off and dangling near the converter. It is too short to reach it. I'm hoping this wire connects to something and the light will work again. Any ideas?

HowieE · 06-19-2010, 08:30 AM

First assumption from the fact you see that wire coming out of the 12 volt panel would be that the Power On Light was 12 volts. Not sure that makes sense since the light would be on any time the battery was present unless there was a separate 12 volt tap on the univolt that was isolated from the battery.

If that was the case you could install a 120 relay on the input side of the converter and use it to switch the 12 volt power to the Power On Light. This would cause the Power On Light to only be on when you had shore power.

A simple 120 volt voltmeter plugged into one of the receptacles would indicate shore power and also monitor the voltage coming in from the campground. If you have an AC that is a much greater condition to monitor. Low voltage, below 105 volts ac, will kill an AC fast

garry · 06-19-2010, 09:52 AM

The Univolt had an output for the power on light and a shunt for the ampmeter if you have the old Univolt you can take the fuse block off and use it for the power on and ampmeter.

Here is how it is done

Univolt replacement

Inland RV Center, In · 06-19-2010, 09:59 AM

Quote:

Originally Posted by garry

The Univolt had an output for the power on light and a shunt for the ampmeter if you have the old Univolt you can take the fuse block off and use it for the power on and ampmeter.

Here is how it is done

Univolt replacement

There is a simple wiring change that's made at the monitor panel, that makes the "power on" light work correctly when the coach is plugged into city power, when a new style "Univolt" is installed.

I will post it later, when I am back in my office.

Andy

Inland RV Center, In · 06-19-2010, 02:35 PM

UNDERSTANDING THE POWER ON LIGHT

1. The power on light IS NOT WIRED to positive voltage on one side ans negative on the other.

A. Checking the wires to the light with the trailer unplugged will show positive battery voltage on both wires. Since the voltage is the same on both sides of the bulb there is no current flow through the filament and it does not glow.

1. The positive battery voltage on one side comes direct from the battery. The positive battery voltage on the other side comes from the battery, through the univolt, and out the power on light circuit to the bulb.

2. The power on light is wired with one side to the positive battery voltage,and the other side to the power on light circuit of the univolt.

A. Checking the wires to the light with the trailer plugged in will show univolt/battery DC voltage on one side and univolt unrectified AC voltage on the other. The reading will practically be the same except one is DC and the other is AC. Example: 12.6 plus DC one side versus 12.6 AC on the other side. Since there is a voltage potential difference between the wires there is a current flow through the filament and the bulb will glow.

1. The positive DC battery current on one side comes direct from the battery. The AC current on the other side comes from the transformer windings in the univolt before the current is rectified.

Now that everyone has that information, it becomes a problem when a new style converter is installed. The following will tell you how to modify the circuitry to make the power on light work again.

A converter with a new name has been used in Airstream trailers and motorhomes, since the end of February 1988. The name is MAGNETEK, and it replaces the Triad/Utrad that was used for many years. The basic design is the same.

All functions and testing remain the same, except for the power on light circuit. In past years, the wiring on the power on light was positive on both sides (read above), and only the difference in voltage potential, AC versus DC, caused the light to function.

On the current Magnetek converters the power on circuit provides 12 volt DC to one side of the bulb and the other side is ground. This 12 volt power is picked up from the 18 gauge wire from the converter.

When a Magnetek is used to replace a Triad/Utrad, the wiring must be changed at the power on light in the control panel. The purple wire to the power on bulb will not have to be changed. The "black" wire WILL have to cut and spliced into one of the white ground wires.

And finally, you can have another swig, make it a long one, of your cool one.

Hopes this squares away the problem.

Andy

john hd · 06-19-2010, 03:32 PM

just made my own power on indicator by using a 12v cube transformer (think cell phone charger etc.) and connected it to the "ac power on" wire in my coach. one side to the black wire the other to negative.

plugged it in right next to the intella power cord and my light is working as before.

note, mine uses a led on the control panel and they are polarity sensitive, just swapped it around until the led lit.

simple.

john

Inland RV Center, In · 06-20-2010, 10:42 AM

Any comments?

Andy

4RXLA · 06-21-2010, 01:16 AM

Thanks Andy for the info. The light is working once again!

68 Overlander · 06-22-2010, 11:08 PM

You can also use somethining that runs on AC plugged into an AC outlet like the microwave clock if installed, alarm clock, cell phone charger, etc that has an LED with it. There is also the Bill Worden wall wart way that John posted above. I have not done it because I have a small clock that tells me when I have AC but it sure would be simple.
http://www.bestconverter.com/assets/...t/Univoltp.pdf

PeterH-350LE · 06-17-2012, 05:06 AM

Quote:

Originally Posted by Inland RV Center, In

UNDERSTANDING THE POWER ON LIGHT

1. The power on light IS NOT WIRED to positive voltage on one side ans negative on the other....................

Hopes this squares away the problem.

Andy

Reviving this old thread to get some input on the intelli charger and the power on light. It does not have its designated 12V current to feed that panel light. Any suggestions for a work around, since coach Battery current is always present, you can not use the 12v charge current of the intelli charger for the power on light

AtomicNo13 · 06-17-2012, 06:02 AM

OK Andy how about this,
I have a 1991 Excella. At some point in history the PO replaced the assumed Univolt charger with an IOTA converter. My "AC power LED does not light, nor do any of the fluid (fresh, grey, black) indicators on my monitor system work. HOWEVER, both LPG, and battery LEDs function normally.
Is there a correlation between the AC indicator (system) not working and my tank sensors not working, or is this just wishful thinking?

Stumped by this...

Inland RV Center, In · 06-17-2012, 07:03 AM

Quote:

Originally Posted by AtomicNo13

OK Andy how about this,
I have a 1991 Excella. At some point in history the PO replaced the assumed Univolt charger with an IOTA converter. My "AC power LED does not light, nor do any of the fluid (fresh, grey, black) indicators on my monitor system work. HOWEVER, both LPG, and battery LEDs function normally.
Is there a correlation between the AC indicator (system) not working and my tank sensors not working, or is this just wishful thinking?

Stumped by this...

There is an answer to correct that issue, but it's at my office.

I will post the answer later today or tomorrow.

Andy

Inland RV Center, In · 06-17-2012, 09:49 AM

Quote:

Originally Posted by Inland RV Center, In

There is an answer to correct that issue, but it's at my office.

I will post the answer later today or tomorrow.

Andy

Post # 5 above, explains the power on light "how to" fix.

Andy

PeterH-350LE · 06-17-2012, 10:10 AM

Quote:

Originally Posted by Inland RV Center, In

UNDERSTANDING THE POWER ON LIGHT
..............
On the current Magnetek converters the power on circuit provides 12 volt DC to one side of the bulb and the other side is ground. This 12 volt power is picked up from the 18 gauge wire from the converter.
..............
Andy

Yes, Andy , post #5 above explains the wiring issues with the old converters and how to fix it with the new Magnetek converters with a designated 18 gauge wire for the indicator light. Intelli Charger do not have the designated wire and have 12v volt power going to the + terminals at all times from the house batteries.
My questions was if there is a way to make it work under those circumstances.

Inland RV Center, In · 06-17-2012, 01:39 PM

Quote:

Originally Posted by PeterH-79MH

Yes, Andy , post #5 above explains the wiring issues with the old converters and how to fix it with the new Magnetek converters with a designated 18 gauge wire for the indicator light. Intelli Charger do not have the designated wire and have 12v volt power going to the + terminals at all times from the house batteries.
My questions was if there is a way to make it work under those circumstances.

Peter.

Sorry, but I have no idea how to make that light work with other chargers.

Andy

lemley · 02-05-2018, 09:26 PM

I just replaced the converter on my '88 with a Boondocker. I have the power on light now working using a method which I think is true to the original design and was quite simple. The "Bill Worden" method has two subtleties. First it shows that the wall wart is AC - not DC. AC wall warts are a bit more rare these days but not hard to find online. The second is that the power on light is shown connecting to ground. As pointed out earlier in this thread, that is a deviation from the original wiring and has to be manually changed for the "Worden" method or others discussed in this thread.

I made the simple change of connecting one side of the wall wart output to the POSITIVE side of the converter rather than to ground.

Thus one side of the power on light is connected to "battery" positive and the other side is connected to the wall wart output - which is the same as the battery positive with no shore power (thus no light) and 12VAC from battery positive with shore power (thus light). Electrically this should be the same as the output from the Univolt and should work with any converter.

A picture of the wiring is attached.

walker · 11-29-2019, 04:00 PM

Quote:

Originally Posted by lemley

I just replaced the converter on my '88 with a Boondocker. I have the power on light now working using a method which I think is true to the original design and was quite simple. The "Bill Worden" method has two subtleties. First it shows that the wall wart is AC - not DC. AC wall warts are a bit more rare these days but not hard to find online. The second is that the power on light is shown connecting to ground. As pointed out earlier in this thread, that is a deviation from the original wiring and has to be manually changed for the "Worden" method or others discussed in this thread.

I made the simple change of connecting one side of the wall wart output to the POSITIVE side of the converter rather than to ground.

Thus one side of the power on light is connected to "battery" positive and the other side is connected to the wall wart output - which is the same as the battery positive with no shore power (thus no light) and 12VAC from battery positive with shore power (thus light). Electrically this should be the same as the output from the Univolt and should work with any converter.

A picture of the wiring is attached.

Please clarify, did you use a ac to dc or ac to ac wall wart? Thanks

lemley · 12-04-2019, 10:43 AM

Thanks for the post. I did this a couple of years ago and sent email to Bill asking him to update the schematic to show negative from wall wart connecting to +12 from converter. He didn’t think anyone used the method anymore. I got a second’88 Excella and could not remember the fix and this jogged my memory.

To the question of AC or DC transformer... definitely DC. The LED on the panel seems to have its - side connected to +12. It requires 12 more volts to light. The old converter provided that. The new ones do not. Hence you can either take down the panel and rework it OR do the simple thing and add the 12 VDC wall wart.

Negative from the wall wart to positive on converter. Positive on the wall wart to the AC sense wire that went from the old converter to the panel. It’s all easily done at the converter.

lemley · 03-29-2021, 12:17 PM

Here is an updated schematic for wiring in an auxiliary 12VDC power supply to drive the power indicator on the overhead display. All of the solid lines are in place. Only the dashed lines need to be added. It can all be done at the converter.

lemley · 03-29-2021, 12:27 PM

I’ve had a few questions about the “wall wart” auxiliary power supply. Wall wart is slang for those little black cubes with a wire coming out of them which you plug in the wall, giving the wall a “wart”.

In this case I’m not referring to the more modern USB charges, although I suspect that one of those should work.

I’ve attached a picture of a wall wart I found laying in my garage.