Question on locating parts for furnace

[Al in michigan]

I think I need a new air switch but not having luck locating one online, many sites say it's discontinued. OK, I did find one but it lists for $156--seems excessive. Are there other places to look? Maybe some way to cross reference to an existing part number ? Or do I bite the bullet & pay.

FS 4225-155 or 42-21582-06

 

[Stuff]

42-21582-06 replaced with 42-21582-92 - $12.60 - https://surpluscityliquidators.com/products/spdt-air-press-switch-35wc.html

 

[Sponsor]

 

[Al in michigan]

42-21582-06 replaced with 42-21582-92 - $12.60 - https://surpluscityliquidators.com/products/spdt-air-press-switch-35wc.html

That's what I was looking for! Ordered it. Found another for $273

Thanks for taking the time.
Al

 

[Al in michigan]

Well..................... seems they don't actually have that part.

Other ideas most welcome.

 

[Stuff]

Sorry as should be easy but sometimes old parts are hard to find.

If you are not sure it is the problem then what else could it be? Most of the time it is not the switch but the hose or clogged port that it is attached to. Also could be doing its job and warning you about exhaust or intake issues.

Otherwise it is rated for .35" WC so could use another manufacturer if you want to take a chance. It is a safety device. https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=Pressure+Switch+.35wc+

 

[Al in michigan]

I'm guessing the switch. Initially I exercised it a few times and it began to work so I thought maybe the internal switch contacts where dirty. It has been ok for a few days now. I made sure the port and hose where clear. Maybe the hose is a bit loose at the connectors. The intake is just the blower motor open to the room and the exhaust seems to be venting ok judging by the look of heated air externally.

My original switch was called out as SPDT (3 connections- C, NO, NC). I don't see that called out on blurbs for possible substitutes. Is that a common configuration and so not always stated ?

 

[Reach4]

My original switch was called out as SPDT (3 connections- C, NO, NC). I don't see that called out on blurbs for possible substitutes. Is that a common configuration and so not always stated ?

Do you have an ohmmeter, and do you know how it was connected previously? If so, you could maybe measure across the terminals that were in service to determine what it is.

 

[Al in michigan]

Do you have an ohmmeter, and do you know how it was connected previously? If so, you could maybe measure across the terminals that were in service to determine what it is.

Yes on the meter and it's still connected. Just trying to see that I order one that is compatible. I can get it connected properly-labeled or not-if it is electrically compatible. OR are they commonly compatible anyway & I don't need to worry about that.

 

[Stuff]

Most pressure switches only have two connectors - equivalent to C and NO. The "8406-086 Bard Pressure Switch .35wc" shows 3 connectors but they are not labeled.

 

[Reach4]

Here is another idea. When things are working correctly, but the blower is off because the thermostat has not been calling for heat, measure the voltage across the switch. If there is voltage across the contacts, the switch is normally open. In that case, during proper heating operation, that voltage should go to near zero.

 

[Al in michigan]

Most pressure switches only have two connectors - equivalent to C and NO. The "8406-086 Bard Pressure Switch .35wc" shows 3 connectors but they are not labeled.

Looks promising, ordered that one, we'll see what happens. Sometimes might be easier to just call the repair guy.