Need help with Ducane


Old 01-05-10, 06:02 PM
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Question Need help with Ducane

Moving this to correct place. I have a Ducane MPGA100B4 that is not igniting. I opened the door to the furnace and found a 20017402 rollout switch was hanging there in 2 pieces. The metal part still screwed in but the plastic part had separated from it. I replaced it with a new exact model hoping that was all it needed, but it didn't do the trick. So, at this point I have double checked the thermostat was wired correctly (I upgraded earlier in the yr but everything tested fine then), the inducer motor is running, I have checked continuity on each side of the rollouts, limit control, and the pressure switch and all seems to be good. I am not seeing any type of orange glow on the electric igniter. I disconnected the gas line to the pilot and no gas is flowing out of the "smart valve". I checked the bleeder on the in side of the smart valve and there is gas there. The ac works fine if that helps. I tried manually lighting the pilot before I disconnected the pilot hose and I could hear some relays clicking when the flame touched the igniter. I can hear relays clicking when I turn the unit on with the breaker. I tried testing the 24V to the smart valve but I am not seeing any voltage through the plug (its been a decade since I used a multimeter so it may be user error), but when I disconnect the plug the relays click and again when i plug it back in. I was thinking it was the igniter, but the igniter not getting gas is making me think there is a problem with the valve, but the multimeter not reading 24V at the valves power plug is making me think board, lol. I disconnected the transformer to check it and everything shut down when i pulled the wire so I'm guessing it is working. I just cant seem to get 24V anywhere and I tested my meter on a AA and car battery and it's working fine. What am I missing? Are there any short cuts to test and find out which part it is? Are there any safety switches I'm missing or any other reason the valve wouldn't start the igniter or not send gas to the igniter?
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Old 01-05-10, 06:26 PM
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Troubleshooting starts on page 12.
Old 01-06-10, 03:15 PM
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Do you have a 3 amp fuse on your board? When the rollout broke, maybe it shorted and took out the (if you have one) low volt fuse.
Old 01-06-10, 07:23 PM
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24 volts

I just re-read your original post. You stated you'd checked the meter with a car & AA battery. They are both DC voltage. You are looking for 24 volts AC. Don't know how a meter would react to AC if set for DC.
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