David,
That "converter" is some sort of solid-state relay box. It takes thevoltages from the turn signals, brake lights, and taillights of the towingvehicle
and uses them to switch on the power to the trailer connector and supplythe power for the trailer lights. Here's the deal:

The towing vehicle has light and brake switches and a signal flasher.All of these are designed by the manufacturer to handle so much current.Putting
the trailer lights on the same switch adds quite a load to the vehicleswitching, causing potential problems, not to mention the old "rapid flashing"
syndrome. Using these voltages to only control the power (through theconverter), not to actually SUPPLY the power, eliminates the potentialfor
problems. It's also fused seperately, so that a short circuit in thetrailer wiring or lights won't affect the towing vehicle.

The lights on the trailer might easily double the loads in the vehiclelighting circuits, but the converter makes that load the same as it was
originally. The current required to switch on the various circuitsto the trailer lights is very low, probably on the order of 100 milliampsor less.
The converters must be pretty simple inside, I'd bet that I could buildone myself with nothing much more than 3 big power transistors, a fuseblock,
and a handful of other components. At what they cost, I probably wouldn'tbother, though.

This problem must be more "potential" than "real", or everyone who towsa trailer would use these converters.

I do have a 30-amp relay under the dash to supply (fused) power to the"Batt" connector on the trailer harness for charging the trailer batterywhile
underway. It does the same thing as those diode isolators, keepingthe vehicle battery from supplying power to the trailer when the vehicleisn't
running. With this system, I have the option of turning the key tothe "Acc" position and the trailer charging system will recharge the vehiclebattery.

Interestingly enough, my A/S had a neat isolator system (disconnectedby the original owner for some reason). It assumed that the "Batt" leadwas
hard-wired to the vehicle battery, allowing it to feed the trailerif the connector was plugged in. However, if the voltage dropped too low(I think it
was 11.5 volts), the relay would open, disconnecting the vehicle batteryso you'd be able to get it started. When the voltage rose above 13.5 asthe
charging system brought it up, the relay would close again, supplyingpower to the trailer.

Along these lines, Jan & Bill Moeller's book claims that you cannotcharge the trailer battery satisfactorily through the standard wiring,as it's too
light weight. (#10 AWG) They rigged up some #4 cable (this is lightweightwelding cable) from the vehicle battery all the way to the trailer battery.
Dunno if they used an isolator, but they probably did.

<<Jim>>

David Newell wrote:

> Jim, Found it, I'm really getting an education.. Do you know whatsin it and how it funtions?
>
> Jim Dunmyer wrote:
>
> > David,
> > Go to http://www.rvpartsdirect.com,click on Catalog, Electrical, Trailer
> > Connectors & Converters, then look at "Heavy Duty Converters"and "Acar Converters"
> > to see what I'm talking about. Dunno if the full URL will comethrough, but I'll
> > try:
> >
> > http://cds.inetbiz.com/cgi-bin/webc/rv/group.htm!?category=4&subcat=3600&subcatname=Trailer%20Connectors%2fTail%20Light%20Converters&sid=2Ql5QL8Wq
> >
> > If you try that one, make sure you get the whole thing. <<grin>>
> >
> > <<Jim>>
> >
> > David Newell wrote:
> >
> > > Jim, the only isolators I'm aware of are the Alternator diodesthat separate the
> > > towing vehicle battery from the trailer battery. The alternatorwill charge both
> > > batteries but won't allow the back flow of juice to affect eitherbattery cause
> > > its a one way street. The signal lights are directly connectedand the electric
> > > brakes go to the controller.
> > >
> > > Denny644@aol.com wrote:
> > >
> > > > Jim,
> > > > your comment on "isolators" needs amplification before it canbe answered.
> > > > you probably WANT signals fed from signal switches. You probablydo NOT want
> > > > the bathroom light hooked to the turn signal however. Whatis it you want to
> > > > do?
> > > > denny
> > > >
> > > > --------------------------------------
> > > > not a Good Thing. (<---Dave, what does this mean?)
> > > > (Denny: Water in your wadders is Not a good thing )
> > >

--

<<http://www.oldengine.org/members/jdunmyer>>
<<jdunmyer@toltbbs.com>>
<<lower SE Michigan, USA>>
<<mailto:jdunmyer@toltbbs.com>>