Problem replacing furnace thermostat

[soohma]

I have a 97Dodge 190 Popular Roadtrek. The thermostat was very hard to control so I thought I'd change it.

I bought a Robertshaw RS1100-72 which has battery backup. It has only two wires, a 'R' and 'W' with the 'R' being the 24 Vac and the other the heater.

I have attached the wires both ways (since I can't tell what's a 'R' and what's a 'W' and when I turn on the power, the furnace comes on, but the little screen is blank and I can't control the temperature.

Any idea what might be the problem?

[SteveJ]

I would contact Robert Shaw to find out if the thermostat will work with 12 volt DC. I'm thinking not. It likely requires a working "C" wire.

I purchased this one about 2.5 years ago. Tighter control than the original.

https://www.amazon.com/gp/product/B0...e?ie=UTF8&th=1

[PeterW]

It should work. The literature says it will work on a millivolt system. Try it with batteries installed but not wired up. It may be defective.

[W9TR]

Should work, it’s rated for dry contact operation and only has two terminals, W and R.