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Kenton Guidry
Kenton Guidry, HVAC Technician
Category: HVAC
Satisfied Customers: 966
Experience:  12 years install/service experience.
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I have a GMP050-3 and the gas furnace will not fire up. The

Resolved Question:

I have a GMP050-3 and the gas furnace will not fire up. The AC works ok.

I replaced the control board ICM280C B1809913S and no change. The rollout and safety detection circuits have 0 resistance. The purge blower runs and the vacuum switch stays open.

Red diode is on solid - purge motor running no igniter action. The igniter shows resistance but does not glow.

Help!
Submitted: 7 years ago.
Category: HVAC
Expert:  Kenton Guidry replied 7 years ago.
Does your ignitor look like the picture below?
graphic
Customer: replied 7 years ago.
no - I checked the resistance and it seems good.
Expert:  Kenton Guidry replied 7 years ago.
What type of ignition do you have?
Customer: replied 7 years ago.
It is a resistive U shape that hangs down into the unit.
Expert:  Kenton Guidry replied 7 years ago.
Does it glow bright hot?
Customer: replied 7 years ago.
NO
Expert:  Kenton Guidry replied 7 years ago.
Is it suppose to glow hot?

I need to know what type of ignition you have.

You either have a standing pilot, a hot surface ignitor, or a spark ignitor.
Customer: replied 7 years ago.
Hot Surface Igniter
Expert:  Kenton Guidry replied 7 years ago.
You need to measure the voltage.

Please let me know what voltage you have to the ignitor.

Customer: replied 7 years ago.
0 VAC
Expert:  Kenton Guidry replied 7 years ago.
Please turn your furnace off. Wait one minute. Then turn it back on. After that watch the furnace start up. You will need to remove one of the panels to observe the following.

Gas furnaces have a start sequence they must go through.

The first step is that the furnace will get the signal from the thermostat to turn on.

Then the induced draft fan will come on. Not all systems have this fan.

After that, if you have an induced draft fan, the pressure switch will close because of the induced draft fan running.

Once that happens your ignition will attempt to ignite the flame.

When this ocurrs is when you need to measure voltage.

Customer: replied 7 years ago.
Question:

The Draft fan is running - does it create a Vacuum to the switch or Positive pressure?

The switch manually responds to a slight vacuum to transfer.

Could it be that the vacuum port in the draft fan unit is plugged up?
Expert:  Kenton Guidry replied 7 years ago.
The switch will react to a vacuum.

It is common for there to be some kind of obstruction.

The ignitor will not attempt to light until that vacuum switch is satisfied from the id fan running.

Kenton Guidry and 2 other HVAC Specialists are ready to help you
Customer: replied 7 years ago.
I will check it - how can i get back to you?
Expert:  Kenton Guidry replied 7 years ago.
Reply here and I will respond.
Customer: replied 7 years ago.
WE HAVE IGNITION AND FIRE AND HEAT!

I ran a small diameter wire down into the vac port on the fan and felt something give.
I blew through the vacuum tube and had free air flowl into the fan assm.

Thank You Kenton......

Henry
Expert:  Kenton Guidry replied 7 years ago.
Wonderful. You are very welcome.