Happy Holidays everyone!
I'm hip that this is an antiquated Lennox Pulse furnace but when we purchased this house 8 years ago it was working fine. Granted I've not been servicing it as I should, and now that winter is upon us, This fault occured immediately following a power blackout. I'm finding that it often fails to turn on within 40- 240 minutes.if at all. I've watched some YouTube videos and I've traced 120VAC from to the Molex connector to the Johnson Controls control board and found that the connector has power the indicator light is not on.
This is leading me to believe that I have a control board fault. I've seen the replacement modules on various sites between $300-$360, but don't want to trip the trigger until I'm sure. Can anyone tell me if I'm on the right track? Thanks and a lift of the lynch lid for your responses.

 

I know we've discussed the hazards of that furnace in the past with you so we'll refrain from rehashing that again in this thread.

Have you checked the 120v --> 24vac transformer ?
Remember the door safety switch when testing.

 

Thanks so much for getting in touch with me. I don't recall our previous conversation, but I know these Pulse furnaces are the bane of many HVAC folks. Indeed, the safety switch was closed, and the breaker was on when I was carefully doing my live wire testing.

 

Ok.... so what about the transformer ?
If the transformer is dead.... so will be the board.

Not just a servicing issue.... a MAJOR recall on heat exchangers and heat exchanger leaking issues. A fatal issue allowing CO to enter the conditioned air stream. You must have that heat exchanger routinely inspected.

 

Not to doubt an expert, but would the heat exchanger interrupt power inside of the control box? The Molex connector has 120 VAC so if this is the case is there an internal switch from the heat exchanger that would interrupt power?

By placing a space heater in the lower section of this G14 (where the Control Module resides) after 3 minutes the Control Module regained power and started the furnace.

 

I suppose that'll be my backyard fix for this until I get the replacement control box.

 

Please stop.
Pulse furnaces were ahead of their time when they were new. Early versions had many issues but most were ironed out later on in their run. However, with that said-
Yearly testing of the heat exchanger is MANDATORY.
There is a specific process to checking a pulse heat exchanger. It involves pressurizing the chamber.
Yes the furnace will run with a cracked heat exchanger. Yes it will push carbon monoxide into the air stream. I’ve been on more then one call with a pulse where the fire department was involved due to carbon monoxide poisoning.
A lot of pulse parts are also becoming obsolete.
Check the heat exchanger BEFORE BUYING ANYTHING.

 

Thanks Roughneck (I'm a former Leatherneck if there is such a thing) I'll see if I can rent a pressurization tool in the meantime we'll muddle through.

 

https://m.youtube.com/watch?v=pBttclAIyKA

 

Thank you for that link. I've seen several of his videos in the last weeks, but that was one I missed. I am familiar though through the service manual I have, of the internals of the combustion chamber. I'm going to try a different HVAC outfit tomorrow and see if they are willing to repair it.

 

What are you going to have them repair?
The heat exchanger really needs pressure tested before doing anything to that furnace.

 

Okay, the skinny is verified by a Lennox technician. The Control Board in the Johnson Controls has a short and this is what's causing the failure. This control bbox has been obsoleted for several years but luckily Baso has a replacement that we've ordered, not before the cooler temperatures in Oregon though. Glad I insulated the pipes shortly after buying this place. I have the house tits on the spigots as well.

 

Okay, we got the Baso BGN891-C1 yesterday and I installed it today. One little hiccup was I initially forgot to press the reset button on the top of the blower fan. It's now working and kicks on much faster when the Johnson Controls board was on it's way out. I'm monitoring the buildup of CO2 with a nearby alarm. Following removal of that board I discovered that it had been a replacement itself. There's a two year warranty on this Baso board and I'm going to keep up the maintenance on this furnace as I get older and on medication for Hypertension I get cold much more easily than I once did. Thanks to every who chimed in on this.

 

It's been a week and no CO2 alarm, and the furnace fires up within 5 seconds of input from the thermostat~even better than when we first bought this place!

 

Great News!
The furnace issues have abated and its running like a champ. Thanks to everyone who chimed in with their ideas!