Furnace converter

[ALAG321]

I have a 1983 TT with a Duo-Therm furnace in it. (I think the furnace is early 90's vintage) Next to the furnace is a transformer/switch combo that I can manually switch from 12v to 110v power to the furnace. The transformer caught fire and burnt out recently. I have searched the internet for a replacement, but cannot find one. This switch combo has printed on the side "Duo-Therm Converter No. 3-16225-002 For use with Duo-Therm model nos. 65925 & 65930 R.V forced air central furnaces only." Since it burned out, the 12 lights in the TT also do not work. Anyone have any suggestions for a replacement?

[Ray,IN]

After some internet searching using the dogpile search engine, I found this DuoTherm parts site: http://www.ducktec.com/duo-therm-furnace-parts.htm
It sounds like a 120VAC>12VDC converter, made by DuoTherm.

[Gary - K7GLD]

The loss of 12 lighting sounds like a fuse or breaker issue, likely caused when the transformer burnt out..

[ALAG321]

Ray, I too found that page, but after posting a request, never received a reply. I think I may just take a voltage meter out there and figure out a way to wire it in 110 full time. Wish I could find the converter though!

[Engineer Guy]

Troubleshooting 101 suggests the switch selected between the +12 VDC House Voltage [Battery] and the +12 VDC from a 110 VAC -> +12 VDC Converter output while also energizing the Converter with a separate set of Contacts on the multi-Pole Switch. If there's a Schematic on the Heater Door, as per usual, then you should be able to confirm what they did at the Factory. The Furnace decidedly runs from +12 VDC. The question is what those Voltage sources are.

The only 'gotcha' I can envision is that they built a little low Voltage AC - the output from the Transformer - to DC Power Supply right on the Furnace Circuit Board. Weird, but not unthinkable, I suppose... In that scenario, an outboard Converter would not work directly.

Then, by looking at the DC Amp draw Spec on the Heater [my 12,000 BTU Furnace is ~3 Amps], use a Converter you find and wire in yourself. I get 'orphaned' Converters/Power Supplies cheap for projects at places like Salvation Army or Habitat For Humanity.

Alternately, wire the Furnace to the +12 VDC output on your TT Converter and be done with it [if it's not that way already]. It will see +12 VDC when you're plugged in. Just think through the desired operation when replacing the Converter and/or Switch. The key is to fully understand the way it's wired now; then duplicate/improve that situation.

+12 Volt Converter Resources

[Senior Chief]

Or, swap out the entire furnace for a good catalytic heater like the Olympian Wave series; no electrical draw and saves a ton on propane.

[564kathleen]

Hi ALAG321,

I don't know if this will help you - but I think Duo-Therm is part of Domestic Corp. Below is the contact email and phone number for Domestic's customer service. You might try rattling that side of the cage - up close and personal.

customersupportcenter@dometicusa.com
Dometic Corporation
2320 Elkhart, IN 46516,
Phone +1 574.294.2511

[Gary - K7GLD]

Originally Posted by Senior Chief

Or, swap out the entire furnace for a good catalytic heater like the Olympian Wave series; no electrical draw and saves a ton on propane.

Unless you really want or need heat to be ducted, as the OEM stuff is - in our case, a non-ducted heater requires leaving bathroom doors open for heating the whole RV. My folks use the catalytic heaters in their RVs - really loved them.