Primary Limit circuit open - DIY Chatroom

thiesnm · 02-02-2009, 09:01 PM

My furnace is running but it isn't pumping out heat. The primary limit circuit open light is blinking. Do I need to call a furnace guy or is this something I can fix myself.

beenthere · 02-02-2009, 09:10 PM

Need to find out what it causing it to open.

Hopw are your air filters.

thiesnm · 02-02-2009, 09:28 PM

The air filter was in backwards and it is dirty and it is kind of deformed. Like blown out.

beenthere · 02-02-2009, 09:47 PM

That may have been the cause.
When I need to change out a limit, I find the cause, and then after correcting that, and replacing the limit. I check to make sure I was right, and have the caused fixed.
Need to check temp rise after replacinga limit.

thiesnm · 02-02-2009, 10:05 PM

What exactly is a limit?

beenthere · 02-02-2009, 10:31 PM

Is this case.
It should be your temp limit.
It got too hot, too many times.

When it gets to X temp, it opens to shut off the burner to protect the furnace and your house.
When it cools, it closes again.
They re a safety device. So they aren't made to cycle the burner all the time. So after opening too many times, they tend to stick open.

thiesnm · 02-02-2009, 10:41 PM

so how do you close it?

beenthere · 02-02-2009, 11:49 PM

You don't.
You replace it.
Its now unreliable.

dac122 · 02-03-2009, 09:10 AM

been is right so make sure you find the cause instead of just replacing it. A worst-case scenarios is a cracked heat exchanger.