I don't have model or serial number cause I could not find them, oddly enough.

Odd call yesterday on a customer where I repaired the A/C last summer. Now back to go through her gas furnace.

Short and stocky Army green upflow two stage Lennox gas furnace with variable speed blower motor. Installed by local Lennox dealer about 4 to 5 years ago. Very poor replacement installation with a ton of holes left open in the existing supply/return duct work which has now been sealed with duct tape.

She has complained to replacement company many times of increased heating/cooling bills but company does not respond, which is typical of this particular company.

In testing/looking at the system there is no heat signal going to w2. The Honeywell TStat is only connected to W1 so I turn it on and waited to see if heating system would go into second stage heat. After 10 minutes it did not.

So I jumpered w1 to w2 and second stage came on immediately. Did this 3 times to make sure.

Seems to me this w2 terminal needs to be involved in the heating signal and does not have a timing circuit as some two stage furnaces do.

Any educated guesses? I wish I has the model and serial but like I said, I could not find them. So your educated guesses would be appreciated.