furnace won't light at elevation and cold

[Weissenheimer]

Concur...from what I have read the "improved' sail switch is the same as the old one but with a different base mount [82 vs 81]....hence, it seems logical to assume that debris [belly button lint ] inhibits the sail switch movement thus it does not make electrical connection and start ignition of furnace. Lower elevations have higher air density and perhaps that increase air mass will move a slightly compromised [clogged] sail switch....

Has anyone actually taken out a sail switch that "failed" to start a furnace and confirmed that the circuit [electrical contact] was defective therefore stopping the electrical furnace starting signal?

I like your theory about the air density. It does validate my experience where I can always fix my heat by cleaning the sail switch, while keeping the ducting installed. Last time I was in the cold fixing my sail switch I did take it fully apart and did take pictures. I also used some sand paper to clean the actual contact because I saw some corrosion, or at least what I thought would be hindering a good contact even without lint in the way. I will try to upload those pics later.

 

[pvstoy]

I do believe someone mentioned this before in another forum and they said the furnace is smart enough to not allow this type of hack. The furnace will refuse to light if that switch is already closed before the blower starts spinning, it knows something is up. But it makes me wonder if a hard wire switch could be manually activated a couple seconds after the blower kicks on, and that would successfully trick it? However you'd have to manually attend your furnace every time it wants to kick back on lol.

Thanks for that information.

 

[Wallowa]

I like your theory about the air density. It does validate my experience where I can always fix my heat by cleaning the sail switch, while keeping the ducting installed. Last time I was in the cold fixing my sail switch I did take it fully apart and did take pictures. I also used some sand paper to clean the actual contact because I saw some corrosion, or at least what I thought would be hindering a good contact even without lint in the way. I will try to upload those pics later.

Back at you....I forgot that at some location there had to be a gap with "points" to complete or open the circuit; or so I thought... Too many years of sanding pitted vehicle points and using a feeler gauge to re-set the gap....I assumed modern circuits had evolved beyond that, but with a mechanical sail switch, I guess it makes sense..would like to see your photos...thanks.

 

[Weissenheimer]

Some of these pics might be upside down. Couldn't seem to fix it after upload. You'll get the idea though. Anyway, Notice the first pic, I don't even have a dog but I know there is dog hair in way of the switch! Apparently the previous owner had one! But do you see what I mean? This heater will circulate all kinds of dust and hair in the small space. Without fail in my case it is always what causes a malfunction, but it is easy to fix and i usually check before trips. Note, I hardly ever have to fully take it apart as you see here. But one time I do think I had a poor connection at those tiny connections inside the switch.

 

[Wandering Sagebrush]

Some of these pics might be upside down. Couldn't seem to fix it after upload. You'll get the idea though. Anyway, Notice the first pic, I don't even have a dog but I know there is dog hair in way of the switch! Apparently the previous owner had one! But do you see what I mean? This heater will circulate all kinds of dust and hair in the small space. Without fail in my case it is always what causes a malfunction, but it is easy to fix and i usually check before trips. Note, I hardly ever have to fully take it apart as you see here. But one time I do think I had a poor connection at those tiny connections inside the switch.

There are pinned threads on photo tips in the Member Support forum. Try this one.

 

[craig333]

I have a dog and no dog hair in mine. But, the suburban has the sail switch in the rear instead of the front.