Lots of those boards on eBay used. The ones on amazon are all sold out.

Usually you can find an aftermarket control board for these for around $100.

Not a big fan of throwing aftermarket boards into heating equipment. They may work absolutely fine but the installer is accepting liability for that install.
Manufacturers will often have approved fixes of product that is obsolete or NLA.

Not a big fan of used boards found online. If they are available it is because something else on the furnace was too expensive to fix. It may work just fine but chances are good that the "good used" board is as close to failure as the one that you're replacing.

Not sure of the climate where the OP lives, but here when it is -30 degrees the damn furnace better fire each time without having to screw with it. Nothing like that nagging doubt about your house freezing up if you are away for a couple of days...

Here is an example of the plenum box/base I mentioned before.
https://hvacdirect.com/southwark-fb1428-support-filter-box.html
These are kind of cool as there is a filter rack built in for easy service and the base can be sized to give the new furnace the same height as the old one eliminating the need to change the supply plenum or the cooling coil location. Another benefit is the furnace has more even return to the blower wheel.

I recently replaced my 17 yo furnace and AC with a new high efficiency vary speed one from Lennox. I am very happy with how it has performed.

No refrigerant? Or no refrigerant worries because it is a newer type?

If he opens the cabinet he'll find a compressor with refrigerant unless they have DRASTICALLY changed since I installed my last one. Geothermal is nice but I'd really like to see the calculations showing a seven year payback.

Got a second opinion and second estimate this morning. The first guy believed me when I said the furnace was installed in 2002. This guy dug a little deeper, checked the serial number, and said it was made in 1998. It has rust in the heat exchanger and in the inducer fan, bad board, and dirty intake pipe, and sagging exhaust pipe. His opinion was the same - patching this one together isn't a great idea, but he'd do it for $600.
It also has a crappy filter box that leaves about an inch of space around the filter and an antique thermostat that the backlight doesn't work any more that I'll still have to live with.
He will replace the system with a Bryant for $8800, including replacing combustion air pipes, proper filter box, and AC lineset plus do some duct work I want done. MrsWD and I are going to have a talk about it.

https://www.bryant.com/bryant/en/us/products/gas-furnaces/926t/#ratings-reviews
https://www.bryant.com/bryant/en/us/products/air-conditioners/127a/#ratings-reviews

Bryant is Carrier and there's Payne which is also Carrier/Bryant. You can get roughly the same furnace being quoted as Bryant for what should be a decent cost savings if you go with a Payne (terrible name btw)
Not sure you'll achieve the SEER or EER of the two speed AC without upgrading your duct system. Most older duct systems wouldn't be sized in a manner that would allow the new high efficiency systems to reach their full potential.

BTW, this thread now has me thinking I should get back into HVAC and get my son setup with a business.

You might ask yourself how long you plan on staying in that house and amortize the cost of new over that time period.

Me?

I like staying warm in the winter (such as it is here in SoCal) and cool in the summer.

YMMV.

When we upgraded to central heat/A/C, my wife didn't want to go the extra and put in the A/C too. I insisted.

When it was 116* this past summer she didn't object to keeping the A/C on even with it set to 80*.

BTW, I'm assuming cleaning the vent pipe didn't fix the problem then?

Does "replacing AC lineset" mean new AC? If so, why do that if you don't need it?

Last year I replaced my 15 year old HVAC with with a new hybrid system. Monthly bills are lower and 10 year parts and labor warranty, yearly service checks included. Piece of mind and no repair bills were worth it to me.

I'll be here until I die, and I'm 68 now, so hopefully a long time. If I'm lucky I'll outlive it.

No, it cycled normally about 4 times, then went back to the old behavior. :mad:
Both techs said the exhaust pipe was sagging and needed to be supported better and re-establish the proper angle. They both commented on what a crappy installation this was.

It's 20 years old and it will be cheaper to do it now than to do it later. Both the furnace vent and lineset require tearing into the basement ceiling. I don't want to skip the AC now and have to do the ceiling all over again next summer.

The tech recommended and priced single stage unit.
He didn't explain why, but he said he didn't think I would actually see 17 SEER from the 2-stage and didn't recommend spending the extra $500. So it's the ducts?
Anyway, the distributor didn't have the single stage, but offered to send the 2-stage at the same price. I said, what the heck, do it.
Is there a downside?

That sounds like a lot of money. If they're doing the entire job, including tearing into the ceiling and repairing it afterwards, might I suggest that you do the demo and then hire a painter to fix the mess after they get done...

Thanks, yes, I would do that. MrsWD would not approve. She thinks since I'm retired I should let people do stuff for me.
The last time she said that (about 10 minutes ago) I said, "OK, go make me a martini." :D
Seriously, at this stage in our lives my wife and I agreed we would spend more time doing what we want to do, rather than doing things we can pay someone else to do. Being lifetime cheapskates and Jack&Jill of all trades, isn't easy for either of us at times.

No downside other than it won't operate as efficiently as it could with the ductwork being sized for these new high efficiency systems. I don't recall what all is involved because got out of HVAC when these two speed systems were really coming on strong in the market but I think the duct system is calculated using different static pressures. The air handler (in you case furnace) having the variable speed fan combined with the 2 speed AC and the properly sized duct system is how you see the 17 SEER which is why whe you read the brochures it will state "up to ..." You'll still be WAY ahead of where you are since the system you're running is likely 10 SEER or less.

Oh man, not a good move :eek:

I'm not retired but I figure if I'm capable of doing something and not doing anything any better at the time, or something that I'd enjoy doing more, I'm saving myself the hourly rate I'd be paying someone else to do the job. I like making $100 per hour even if it's done by not paying someone $100/hr.

Trust me, the intrinsic worth of each hour increases linearly with age