2015 Heartland Cyclone 4200 Furnace turns on but blowing cold - can't locate sail switch

J

jasonmayer79

Member
I can't seem to locate the sail switch, and believe this is the root cause of my issues. I'm thinking it's just not making contact, and needs to be blown out. I pulled the exterior panel off, and there is no visible sail switch to be seen. I'd upload a couple pictures, but it says I have to provide a URL, and have no idea how to do that. Any suggestions are greatly appreciated.
 
danemayer

danemayer

Well-known member
Hi jasonmayer79,

The furnace sail switch is located next to the blower cage. The cage is covered by a large 1/2 round shroud.

The sail switch closes when airflow from the blower reaches 75% of normal output. If the sail switch doesn't close, or electrically fails to close, the furnace, as a safety feature, will not turn on the gas valve or attempt ignition. I'm not sure if the blower continues to run for more than a few seconds if the sail switch doesn't close.
 
J

jasonmayer79

Member
danemayer said:
Hi jasonmayer79,

The furnace sail switch is located next to the blower cage. The cage is covered by a large 1/2 round shroud.

The sail switch closes when airflow from the blower reaches 75% of normal output. If the sail switch doesn't close, or electrically fails to close, the furnace, as a safety feature, will not turn on the gas valve or attempt ignition. I'm not sure if the blower continues to run for more than a few seconds if the sail switch doesn't close.
Click to expand...

how do i upload a picture so i can show you what I'm working with over here? I opened up that area, and the area to the left is the water heater area. There's no sign of a sail switch, and i can't seem to find out how to upload a picture to help.
 
danemayer

danemayer

Well-known member
jasonmayer79 said:
how do i upload a picture so i can show you what I'm working with over here? I opened up that area, and the area to the left is the water heater area. There's no sign of a sail switch, and i can't seem to find out how to upload a picture to help.
Click to expand...
The anti-spam features of the forum software won't let you upload pictures for a few more posts. You can post a picture to another site, like google drive, and link to the picture.
 
LBR

LBR

Well-known member
First picture...that wire by the SFV 35Q sticker. That is the sail switch. Disconnect those 2 wires, take out 4-5 screws and remove the big plastic squirrel cage/cover. Sail switch is inside it.
 
J

jasonmayer79

Member
LBR said:
First picture...that wire by the SFV 35Q sticker. That is the sail switch. Disconnect those 2 wires, take out 4-5 screws and remove the big plastic squirrel cage/cover. Sail switch is inside it.
Click to expand...

Thank you so much, LBR! I'll give that a go in the morning, and report back with what I was able to find out....or destroy. :)
 
6

6.7LMegaCab

Well-known member
Out of curiosity, you say it is turning on, but is it cycling? It seems like mine will turn on and blow cold air when it runs out of propane. It doesn't stay on too long though, maybe a minute or two, if that. When I think I should have plenty of propane left, I overlooked that as being a culprit more than once.

Sent from my SM-G955U1 using Tapatalk
 
danemayer

danemayer

Well-known member
The module board will then verify that the sail switch circuit is closed and motor is upto speed. If this circuit remains open for 30 seconds after the blower motor starts, the
module board will go into lock out and shut down the blower motor.
Click to expand...

According to Suburban, if the sail switch doesn't close and pass power to the control board, the blower will shut down rather than run continuously.

But it also says:
3. The module board also performs the lockout function in cases where thespark fails to light the burner. When lockout occurs, the spark stops, the
voltage from the module board to the gas valve is discontinued, and the
valve closes. The unit will remain in lockout and the blower will continue to
run until the thermostat is turned off. Turning the thermostat off disengages
the lockout function of the module board. After the blower has stopped, the
ignition sequence can be started again. The module will try three times for
ignition before lockout.
Click to expand...

So perhaps the problem is not with your sail switch, but rather with failure to ignite. It will make 3 attempts to ignite before locking out. If standing next to the furnace I think you can hear the gas valve click when energized.

Page 6 of Gary Brinck's Furnace Troubleshooting Guide in this folder describes a full list of possible causes.
 
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