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Morham 11-03-2007 08:42 AM

Help with Furnace. Bad IPI?

First time on the board so thanks in advance!

I have a Lennox G23Q2/3-75-1 unit with the Johnson Controls G776RGD11 IPI. Also, I have a mercury switch thermostat.

It's an odd one here guys and gals. The furnace will run fine for hours and then stop. When it stops I have no 24VAC at the thermostat (measured with meter when the problem first started). When I suspect it has stopped I can verify by moving the fan switch to ON and the fan doesn't come on.

To reset and get things back to normal, I set the thermostat to below room temp, move the fan to ON and wait for a few minutes until I hear the fan start working again.

When the fan starts working again I can move the thermostat above room temp and everything is back to normal. The furnace works like normal and I can return the fan switch to AUTO.

I have noticed that if I don't return the fan to AUTO it will continue to heat and not break. But obviously I don't want to run the fan 24-7. The problem only happens when I return the fan to AUTO.

Any ideas??


cjett 11-03-2007 11:27 AM

Sounds like the sub base on your t-stat is bad. Might be a good time to install a digital t-stat if you are still using an old style.

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