Furnace for Landmark 2010

DruidZ

Active Member
We just returned to Canada and the furnace has failed. It seems that these thnigs are scarcer than hen's teeth. Can anyone tell me if an SF-42Q will work in place of my SF-42?
 

NP_Chief

Well-known member
I believe the only difference is that the "Q" series is supposed to run quieter. The units are the same dimensions.
 

CDN

B and B
Hello,

What is wrong with it? Might be something like a heat exchanger that is rusted through and safety related?
 

DruidZ

Active Member
What is wrong with it? Might be something like a heat exchanger that is rusted through and safety related?

It doesn't look like it. So far three people have looked at it and have given me three different diagnoses.
 

danemayer

Well-known member
This is the first I've ever seen about parts not being available for an SF-42, which is not even that old as things in the RV industry go. The most common failures are on the blower, the control board, loose wires, the sail switch, and the high-limit switch. All of those parts are readily available.

Can you describe exactly what happens or doesn't happen when the thermostat calls for heat. In normal operation, the thermostat calls for heat, there is a relay overhead above the air conditioner air return that clicks, then the furnace blower starts and runs for about 25 seconds. There are up to 3 ignition attempts. If successful, hot air will start flowing within a few seconds.

What does yours do?
 

danemayer

Well-known member
Absolutely nothing.

If you're not hearing a click from just above the air return, it might be a loose wire at the thermostat. It could also be the relay in the gray box above the air return, but that's a very low likelihood. But it's not a very loud click, so it's easy to miss.

Has anyone checked the 12V DC fuse for the furnace, in the main fuse box? If it's blown, the furnace symptom will be "absolutely nothing".

Also, does your refrigerator work ok? Does your water heater work on 12V DC (not 120V AC). If they're also failing, you have a more general problem with the 12V DC power.

If the fuse and the 12V DC are ok, the most likely causes of furnace failure are 1) loose wire where the furnace wiring connects to the trailer wiring (usually on top of the furnace, or 2) bad control board - replacements are readily available - most current version is less than $100.
 

DruidZ

Active Member
If you're not hearing a click from just above the air return, it might be a loose wire at the thermostat. It could also be the relay in the gray box above the air return, but that's a very low likelihood. But it's not a very loud click, so it's easy to miss.

The guy did check the thermostat.

Has anyone checked the 12V DC fuse for the furnace, in the main fuse box? If it's blown, the furnace symptom will be "absolutely nothing".

It was blown but we replaced it. I do not believe that it was blown when the first guy started looking at it.

Also, does your refrigerator work ok? Does your water heater work on 12V DC (not 120V AC). If they're also failing, you have a more general problem with the 12V DC power.

Everything else on DC is working fine.

If the fuse and the 12V DC are ok, the most likely causes of furnace failure are 1) loose wire where the furnace wiring connects to the trailer wiring (usually on top of the furnace, or 2) bad control board - replacements are readily available - most current version is less than $100.

It was the control board that I first started looking for because that's what the first guy said was the problem. Everyone was out of stock and if they had them they were anywhere from $200 to $300+.

I have decided that with all of the hands in there I may as well just get the new one and be done with it.
 

DruidZ

Active Member
There's a Suburban universal board 521099 that sells for $79.07, in stock. It's backwards compatible and replaces the older more expensive board.

Wow. That might have been what we needed if we knew about it while we were still in Kentucky. Unfortunately we had to get back to Canada and it was cold here and we started rushing some decisions.

It may be that the people working on the furnace made it worse but at this point I am going to accept it as an expensive lesson in what I should have done - go to this forum the minute it stopped working.
 
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