Control troubleshoot


Old 12-30-18, 04:28 AM
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Control troubleshoot

I accidentally cut my thermostat wire while doing some work on the house.

After fixing the immediate problem and reconnecting the thermostat, my gas forced hot air furnace still won't operate. The blower fan stays on but the gas never comes. The control board reports that it is an "open rollout" (6 flashes of the little LED). I checked the rollout switches and they are NOT open and do not need to be reset. I jumpered the wires that go to the rollout switches and everything still behaves the same.

So I'm thinking that since the control board says the rollout is open, and the rollout really isn't open... I must have a fried control board.

Any ideas of other things I can check or do? I broke it Saturday, it's now Sunday, and the pros can't make it until Wednedsay... that's a long time with no heat when living in New England.
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Old 12-30-18, 07:11 AM
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Talking Fixed!

It is fixed!

In case anyone searching for a similar issue falls upon this thread, here's the deal - when a thermostat wire gets shorted out, it's apparently fairly standard for there to be a fuse on the control board that will blow. Or you bake your 24V transformer. In my case, the transformer was fine and the fuse was blown.

The fuse is a purple thing with two blades at the bottom and an "E" on the top. This is a standard 3 Amp automotive fuse. I could tell it was baked because when I pulled it out and looked from the bottom, I could see that the wire between the terminals was broken. You could also tell because the purple fuse had a little black mark on it. So I didn't need to wait for a service call, I ran to my local auto parts store, found the exact same thing, and replaced it. Everything seems to work fine now!
Old 12-30-18, 11:05 AM
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Welcome to the forums.

Good job. Thank heaven for the fuse because they don't all have one.
If there is no fuse.... the transformer fries.

The is a 3 on the fuse...... for 3A.
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