I have a Coleman mid-efficiency gas-fired (propane) furnace tubular heat exchanger downflow hot air system. For about a month now I have had a intermittent problem with my furnace failing. The blower comes on with out any heat and produces a rapid red flash error code. This error code indicates: Twinning error, incorrect 24v phasing. The furnace is not wired for twinning. There is only one furnace. The failure occurs if the thermostat is in the off position or in the heat position.

I called a service man and he replaced the control board, which he said was no good, but it still failed. Then it was discovered that the electrical outlet where the furnace plugs in had a bad ground. I had an electrician replace the outlet and he checked the ground at the panel box and the actual ground wire that goes into the ground. Everything checked sound. It still failed. The service man said the problem was probably "transient voltage". I had the power company monitor my line from the power pole to my meter and everything checked okay.

I am at my wits end. Any ideas what it could possibly be?

The newer furnaces are polarity correct. The neutral wire from the breaker box needs to be the same with the furnace. Is the furnace on its own circuit? If not it needs to be. You will get low voltage if other appliances are running at the same time the furnace is which in turn will give high amp draw on the furnace to get the same symptom.

This will take a bit to solve... 1st thing with a volt meter, check at your service switch ( power into the furnace) check from the neutral (white) to ground (green), you should see no voltage ( or close to "0"volts) and from the black (hot) to neutral (white) 115 to 120 volts. If this is correct proceed to the following. Check the furnace 24 volt transformer, be sure that the black (hot) and white (neutral) primary side of the transformer are on the correct connections on the fan board, as per the wiring schematic. Next check the secondary side of the transformer ( 24 volt output wires are on the proper connections on the fan board. If all of that is correct, take off all of the t'stat wires off the control /fan board ( with the power off, and mark on a piece of paper the letter code and wire color. Now put a small jumper wire from the R terminal to the W terminal on the fan/control board, turn on the power to the furnace. See if it runs correctly? If so the problem is in the T'stat or related wiring. What causes the error code of "twinning, polarity error" is when you have either the 120 volt feed to the furnace Black and white reversed or with two furnaces twinned together, you have two 24 volt transformers not in polarity, or the t'stat wiring not in polarity, and as well, a furnaces 24 volt transformer installed wrong. . If this does not solve your problem, post you model number of your furnace for me... I'll look up the wiring schematic

My mode is a Coleman # G8T06012DNA11A.

I didn't mention this before but, when the service man replaced the control board he said that the replacement was an upgrade. The previous board did not store fault codes. The new one does store vault codes. While getting the model # I noticed that the fault code (label pasted on inside of furnace) for the old board for a rapid red flash was low flame sense signal. The fault code of a rapid red flash is twinning error, incorrect 24v phasing for the new board. I don't know if this is significant or not. Can a board be upgraded on a furnace and take on new fault codes?

No, a new board can't take on the old error codes, but if the problem that caused the first board to blink an error code, and the problem is NOT corrected, the new board will see the same problem, and flash the same code... they are all programed into the logic chip on the board. In other words, the original problem still exists...

A fault code can and may change with a control board upgrade(retrofit). For instance a code 13 may have been limit lockout on the old board but code 13 with the new board may be secondary fuse open. That's the reason for the new code sticker and wire diagram it all or part has been changed.

I just ran into this problem today. I installed a newer board in my York Diamond 80 residential furnace. The secondary of the 24V transformer wasn't marked at all so I reversed the 2 wires, applied power, AND IT WORKED! It was wired the other way with the old board and it didn't care about "phasing". Try switching those to see it if helps your problem.

I just flipped my circuit breaker, disconnected the white & black, blew on the ends like a Nintendo cartridge in 1988, and put it back together - and it worked! Score another victory for the patented "take it apart and put it back together method".

50% of the time, it works every time.