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M Oglesby
M Oglesby, HVAC Technician
Category: HVAC
Satisfied Customers: 2038
Experience:  Universally Certified HVACR Technician
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York furnace wont light. Ignitor will cycle on, but no flame

Customer Question

York furnace won't light. Ignitor will cycle on, but no flame will light. I smelled gas at the beginning of trying to fix this, but not now. Cleaned the flame sensor... but no luck with that.
Submitted: 4 years ago.
Category: HVAC
Expert:  M Oglesby replied 4 years ago.

M Oglesby :

When you tried to light with a lighter, did the burners light?

JACUSTOMER-glt1q0r9- :

no

M Oglesby :

You may have a open limit switch.

JACUSTOMER-glt1q0r9- :

which means...

M Oglesby :

The Main limit switch is a rectangular or square looking device that has two wires attached to it and is usually located inside the furnace cabinet on the back panel wall.

M Oglesby :

Locate it and let me know when you find it.

JACUSTOMER-glt1q0r9- :

black rectanglular shaped plate made by texas instruments?

M Oglesby :

Yes that is it! Just to verify, is there a number such as this on it? L240 - 40F?

JACUSTOMER-glt1q0r9- :

just a sec

JACUSTOMER-glt1q0r9- :

l140f-30

M Oglesby :

That is it.

M Oglesby :

Remove the two wires and use a piece of wire to jumper them together.

M Oglesby :

While they are jumpered together, attempt to turn the heat on.

JACUSTOMER-glt1q0r9- :

then it will work?

M Oglesby :

We don't know yet. This is a troubleshooting test.

JACUSTOMER-glt1q0r9- :

gotcha

M Oglesby :

Let me know what happens.

JACUSTOMER-glt1q0r9- :

gave it a shot, jumped the wires together... nothing different happened

M Oglesby :

Place the wires back

M Oglesby :

Use a volt meter to see if the gas valve is receiving 24 volts when the igniter is glowing.

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