No more Univolt!

Excella CM · 06-04-2006, 06:37 PM

I changed out the original Litton Industries converter (Univolt in AS parlance) this week end. It had begun to hum and has always had a tendency to boil the batteries when the trailer is parked for any long period of time. I replaced it with a WFCO 65 amp. unit. Beside being lighter (7# vs 40#) the WFCO has an automatic 3-stage charging regime that is kinder to the batteries. The one problematic difference is that there is no output to the "AC ON" pilot on the control panel to indicate when shore power is connected. I found a simple remedy which is as follows: I found a small 12VAC "wallwart" type plug-in transformer such as is used for many small appliances, etc., and pluged it into the other 110V receptacle where the converter draws its power. I connected one side of the output (doesn't matter which-AC is always changing its mind anyway) to the converter ground lug, and the other side to the pilot light line. Whenever there is 110V power connected, the little transformer lights up the pilot light! Simple, cheap, and effective-no brainer solution.

bhayden · 06-05-2006, 12:20 AM

>>> I connected one side of the output (doesn't matter which-AC is always changing its mind anyway)

Uh, yes it does. One leg should be "hot". That is a sine wave oscilating from + to -. Half the rated voltage if it's full wave recified. The other pole is return which should be at the same potetial as ground.

If the bulb on the panel is rated for DC then you're essentially turning it on and off either 60 or 120 times a second depending on if it's full or half wave rectified and assuming it's 60Hz. A 12 DC bulb won't hold up to this for very long.

Buttercup · 06-05-2006, 02:33 AM

I may be mistaken but wasn't the "AC ON" pilot light supplied A.C. power anyway from a tertiary winding on the Univolt? I don't have a schematic for the univolt and have never seen one but that is the impression I had.

I can look into this as I still have my old unit sitting around. I could take it apart and see what is what...

Excella CM · 06-05-2006, 12:31 PM

My Univolt was a Litton Industries unit with two low voltage windings. the telltale line for the pilot was connected one of them on the upstream side of the rectifier. The output for the telltale was 12 VAC. This is why I used an AC wall-wart. I suppose you could use a 12VDC wallwart and run the hot side to the bulb. Six to one, a half-dozen to the other?

uwe · 06-05-2006, 04:54 PM

Quote:

Originally Posted by Excella CM

I suppose you could use a 12VDC wallwart and run the hot side to the bulb. Six to one, a half-dozen to the other?

More like 12 to one, two sixes to the other.....
It does not matter. Lamps don't care if it is A/C or D/C, so long that the nominal voltage stays around 12V. Different story altogether with electric motors.

mikeandbecky · 08-02-2007, 03:05 PM

So, which is it? Would it destroy the AC ON lamp in the display panel it a + AC line was hooked up to it. I have the grey wire dangling because I have also removed the Univolt, and (soon) will be replacing it with a WFCO 3 stage converter. Or, maybe Ill leave it dangle, and go with Excella CM's idea with the " wallwart ".

AirConditioner · 08-02-2007, 03:34 PM

This might be of help to you from the "Best Converter" site"

http://www.bestconverter.com/assets/...t/Univoltp.pdf

Excella CM · 08-02-2007, 03:55 PM

The "dangling" grey wire is the feed to the "AC" on light on your control panel. Modern converters do not have a tap for this so you have to work around it. The wallwart is simple if you use a 12VAC type. Just connect the 110 VAC side of it where the converter gets power(if you have a duplex box, just plug it in) and run one side of the 12 VAC output to ground (you can use the one on the converter) and the other to the left over dangler. When the converter gets power so does the wallwart and the AC pilot will light.