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jackikevin · Oct 13, 2008, 02:33 PM

I am having problems installing a programmable thermostat. I have a Coleman Evcon Presidential Gas Furnace and a Riverbend a/c. The current thermostat is a Coleman, I'm not sure of the model number, but it is boxy in shape. We originally purchased a Hunter programmable thermostat from Wal-Mart. When we took the old thermostat off, we discovered that there are only 2 wires. 1 red, 1 white. We hooked up the Hunter per directions, turned the breaker back on, and the a/c ran non-stop. We had to turn it off at the breaker. We put the old thermostat back on and took the Hunter back to Wal-Mart. We went to Home Depot and asked for help selecting a programmable thermostat that will work with the 2 wires. We explained to the guy the problems we had with the other one, he recommended a RiteTemp Universal Thermostat (programmable). We got it, installed it per directions, turned the breaker on... :mad:... a/c still running non stop. We tried to cancel the pre-set program... nothing has worked. I am at my wits end and so close to believing that we are doomed to never have a digital/programmable thermostat as long as we have this furnace. The on/off switch is on the furnace, so is the fan on/auto and the heat/cool button. Can anyone help us? Thanks!

MarkwithaK · Oct 13, 2008, 04:10 PM

Originally Posted by jackikevin

When we took the old thermostat off, we discovered that there are only 2 wires. 1 red, 1 white.

Something isn't right here. If you only have 2 wires then I don't see how you're A/C ever worked.

KISS · Oct 13, 2008, 04:17 PM

Some furnaces do the heat/cool selection at the furnace. If this is so, you have to connect Y to W and connect the pair to one wire.

Take Rc and Rh or R and connect to the other wire.

MarkwithaK · Oct 13, 2008, 04:21 PM

Well that would be a new one on me. Interesting.

mygirlsdad77 · Oct 13, 2008, 04:46 PM

Must have a fairly old coleman . They haven't used the heat cool switch at the furnace for years. But they are still out there and KISS is dead on as far as wiring goes.

KISS · Oct 13, 2008, 05:52 PM

You will have to make certain that the mode of the t-stat and the mode set at the furnace matches.

If the furnace is in cool and you set the t-stat for heat, the AC will run forever.

jackikevin · Oct 15, 2008, 01:49 PM

Originally Posted by KeepItSimpleStupid

Some furnaces do the heat/cool selection at the furnace. If this is so, you have to connect Y to W and connect the pair to one wire.

Take Rc and Rh or R and connect to the other wire.

Ok... I'm slightly confused. If we pair the two wires together, where on the thermostat do we put them in at? And we are supposed to put a jumper in RC and RH? This thermostat doesn't have a plain R. Does this question make sense?

KISS · Oct 15, 2008, 01:54 PM

Exactly.

R has been used in the past. To accommodate dual transformer systems. One for heat and one for AC the designations of Rc (Cooling) and Rh(Heating) have been introduced. Shorting Rc to Rh makes it an R terminal.

jackikevin · Oct 15, 2008, 02:01 PM

Ok... but where do we put the paired wires? Do they go into RC, RH, or W? Sorry for asking what seems like a stupid question, but I have no clue when it comes to this stuff.