Lennox furnace problem

[nvr2old]

forget timer setting. the second stage board is set for what operation, one/two/timed?

[grovecreek]

w2 timed

[nvr2old]

did you remove stat from circuit and operate directly at circuit board?

[grovecreek]

No I did think of that later that I should have taken the stat out of the circuit and just jumpered it at the board.

[nvr2old]

thats the place to start. could be stat,wire between stat and furnace. if something chatters its usually because of low voltage,short or conflicting signals.

[grovecreek]

High fire pressure switch is cutting out after about a min.
I checked pressures with a monometer it does go down after the furnace heats up for awhile. I checked all over the heat exchangar for cracks but had no luck. I would like to go back and take apart the collector box area to see if there are any problems in that area.

[Wirenut]

Grovecreek
When the G32's first came on the market I had one do almost exactly the same thing. I changed the circuit board and it still had problems. The problem with that furnace was a improper ground, just thought I would throw that out there, it is an easy thing to eliminate as the problem or correct if it is.

[mike3]

From past experience with T-87's I would encourage setting heat anticipator with a meter. Just thinking out loud. What would the amp draw be from Low to High fire??

[Edited by mike3 on 02-10-2005 at 10:04 PM]

[smittaa]

Have you pulled the flue to make sure its all open. Sounds like high fire pressure switch dropping out.

[airredlands]

Call Lennox Customer Support @ 1-800-453-6669. Have the entire model and serial numbers ready. Ask if this was one of the units that had the combustion blower motor recalled for that very same problem. I must have changed out about 20 or so due to the very problem you are describing.

[grovecreek]

Yes I did go through tech support out of Texas we have it narrowed down to pressure dropping as the furnace heats up. When you pull the vent pipe off it is even more free flowing So the furnace combustion area is sucking in fresh air from somewhere.