Hello,

The title is a bit misleading... Some background. My Dayton furnace (less than 3 years old) had been working fine this winter. Yesterday, I caved and turned on the A/C, which was also working fine last summer. I noticed that the condenser was not kicking on. I checked the furnace and it was throwing 5 reds, which the panel states as a 'Rollout Switch open/Fuse open'. This seems odd considering that I am using A/C and not the heat.

Troubleshooting that I've done:

1. Switched the break on/off several times (had breaker off overnight and turned on this morning to the same problem)

2. Bypassed the rollout sensors completely (note, this was just for a test. I know to never bypass sensors that could save your life someday)

3. Checked the voltage of the Yellow and Red wires from the stat on the main board. This states at 0 the whole time

4. Changed the stat batteries with working batteries

5. Completely pulled the thermostat from the wall

After number 5, the furnace unit still turns on when I turn the breaker on. Seems like something is completely wrong with this system. Could it possibly be the controller board?

Thanks in advance,
Shawn

Sounds like you have a low voltage fuse open on the control board. On some of the newer units the blower will run all the time if you have a limit open or a loss of 24v. You need to check for 24v from R to C or at sec1 and sec2 on the control board.