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I have a DGAT056BDF EVCON gas furnace W/AC. This morning the blower started cycling with no A/C outside unit running. Comes on for a few minutes, off for 30 sec and then back on.

Since it's cool outside I switched it to heat. Heater came on and brought the house up to temp and went off. The blower does the same thing. Turned the system off at the T-stat and still the blower cycles.

Bad Board? The board in it is PN 7990-320 . If you think it's a bad board I'll put one on order immediately. If not please let me know what else to check.

Thanks much for the help

Greg

The board controls all blower operation unless you are running the air conditioner. When the blowers comes on for heat is it a slower speed than for air conditioning? If so, when it comes on when it is NOT supposed to, is it the lower heat speed or the higher air conditioner speed?

Dale, The blower is the same speed for heat or air. It's been that way since we bought the place five years ago.

Update: Yesterday I turned the power off at the control box and left if off all day. Last night around 6 pm I turned it back on as I wanted to cool the house down.

To my surprise it did it's job and when it shut down it did not cycle. It didn't do it all night and this morning I turned it to heat and so far no cycling. I'm stumped. Think it's the board going south?

Dale, you asked about the higher fan speed for A/C or lower for heat and I said there wasn't a difference. So this morning when I kick in the heat I took note if there was a difference and there might be a slightly lower fan speed on heat. When I kick in the A/C today I'll check again to see if I feel a difference in air movement.

I may go ahead and order a new board just to have on hand if this one goes south. We all know how that goes. The thing will go out when the weather is the worse. Thanks for the help. Greg

Dale,

I did check and there is no differance in fan speed between Heat or A/C. It worked fine all day all day yesterday and last night. I'm still stumped on what's going on.

Greg I think you are running too high of a blower speed for heat. Usually the speed setting for heat on that furnace is either medium, if a 3 speed and medium-high if a 4 speed blower.

Thanks Dale!

Now how do I check where the speed is set on the blower? Is it on the blower or a setting on the board?

Thanks
Greg

There is a series of terminals on the bottom of the board. From right to left they are labelled on the board: L1/xfmr, L1, cool, heat. The terminals cool and heat are where the blower gets it power for cooling and heating. If you have a jumper between cool and heat and ONLY 1 wire coming from the white Molex plug on the left side of the electronics housing then you are running ONE speed for heating and cooling. Most of the time the black wire from the plug is on cool and the red wire from the plug is on heat. IF YOU HAVE A DOUBLEWIDE, you will need high for both heating and cooling, leave it alone.

Dale, Yes there is only one white wire coming out of the molex plug. Since I posted this the blower has not cycled and has been working fine. Go figure.....

Again Thanks!