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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 7743
Experience:  Furnace, A/C and heat pump specialist.
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Pilot light comes but not the burners

Customer Question

pilot light comes but not the burners
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Do you have a volt meter to see if we are getting 24 volts too the gas valve?

Customer: replied 1 year ago.
Expert:  airheatman replied 1 year ago.

OK is the pilot a glow bar ?

Customer: replied 1 year ago.
pilot
Expert:  airheatman replied 1 year ago.

I am not having much luck finding a manual on the furnace. Does it have a control board?

Customer: replied 1 year ago.
there are 3 wires to the gas valve, unit is about 9 years old
Expert:  airheatman replied 1 year ago.

Is there a wiring diagram you can send me a pic of? And on call for heat see if we are getting 24v between the Common and Main valve terminal on valve?

Customer: replied 1 year ago.
it has a control board anda honeywell s8660k box
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  airheatman replied 1 year ago.

Lets check between MV-MV/PV for 24 volts

Customer: replied 1 year ago.
no voltage between mv and mv/pv
Expert:  airheatman replied 1 year ago.

Make sure all the connections between the module and gas control are clean and secure, Try unplugging and re plugging as they can develop corrosion and not make good contact.

Customer: replied 1 year ago.
the pilot light seems to come on more often if i cycle the on-off gas valve.
Expert:  airheatman replied 1 year ago.

Are you saying the pilot does not light everytime or it just turns on and off during the same call for heat?

Customer: replied 1 year ago.
does not light everytime
Expert:  airheatman replied 1 year ago.

Based on this I am suspecting the module is going to need to be replaced.

Expert:  airheatman replied 1 year ago.

Erratic behavior as well as not ever getting the 24v out to mv once the pilot valve has opened is characteristic of a failing board.

I can open this to other experts to see if they have more ideas if you would like.

Expert:  airheatman replied 1 year ago.

Below is my flowchart for the 8660

Customer: replied 1 year ago.
thank you I will order a new honeywell s8660k.
Expert:  airheatman replied 1 year ago.

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