We have a 15 yr old furnace.

A Harmony II thermostat for zone control

A Lennox digital thermostat for the upstairs,honeywell dial type for the down.

We have disconnected the zone control as per our furnace installers directions.

While the upstairs digital is set for 72 the furnace doesn't want to kick on,most times we have to throw the power switch and wait for a minute,turn it back on,the system purges,and then runs smoothly for many hours.

The system normally has problems during those really cold nights,and getting up at 3 am to restart is a hassle.

Our local installer doesn't seem to be able to repair this problem,they have been here quite a few times in the past 2 years,we don't think they are well versed on Lennox furnace troubleshooting.

Any ideas?

KBC

Just wanted to say sorry you have a lennox pulse. Get rid of it. They are overbuilt(meaning they have to many things to go wrong for the cost of the unit). They have always been problem prone. Not to mention hard to work on. Put in a goodman, or really any new furnace, and sleep better at night.

Don't take my word for it ( I just hate lennox, period, especially the pulse), I hope you can get some good advice from the other experts on this site, that are a little more comfortable helping with the pulse.

Unles you can find a local Lennox pulse expert you are toast. I have worked on many pulse furnaces and went to Lennox school many years ago for a course on servicing this style of heater. BTW part of the engineering is from the old WWII german rocket propulsion systems. Just mini explosions for sure. I will not attempt to school you in the repair of these units because there is just to many items that can cause problems and adjustments are CRITICAL.

One simple item to check to make sure all ground connectiond inside the furnace all the way back to the electric panel are good.

Next time you get it to start remove the access panel where the ignition modual is installed. They had a problem with the moduals overheating and sometimes leaving the access panel off allows the modual to run cooler. These are simple tricks to try but that is all I can offer you since into other items can get you hurt.

Just curious hvac, would you ever recommend a lennox pulse to anyone.

Not really. I have turned them down on state inspections so many times because the installers fail to use the factory stainless flex gas line connector or failed to follow the venting instructions. These baby's do vibrate and the vibration can be so low it is hard to feel but will actually vibrate a black iron gas line loose at the union ( I am a witness to this on a house fire inspection). That is the reason for the flex gas line I believe.Actually they are not a bad furnace but many service people are afraid of them due to some bad and sometimes truthful rumors.

With all the new high efficiency furnaces available today that are less of a problem I would not recommend Lennox on that basis. I will say this when they are adjusted correctly they will run like a scalded ape and have very good efficiency.

We still have one at the university. More of a curiosity than a working test model for the students.

Agree

Upon 4 'trial and errors' we have FINALLY found a solution,the 'Mother board' which controls the ignition has been the last line before the replacement.

The installer(a new one,as the previous was just not in tuned well enough) has to go from A to B to... etc,till we had the expensive part put in,so much for saving money on a 'High efficiency' furnace.hehe.

No problems for 1 month now(and not even a bill yet!! )

If only, right?

I hope it keeps running so you get some of your repair investment back.

Glad you got er fixed. I also hope it works for years and years.