Heil 5000 High Efficiency Natural Gas Furnace Not Igniting

ndelancie

I have an old Heil 5000 High Efficiency natural gas furnace in my house that worked yesterday and now doesn't. Now, when the thermostat tells the furnace to turn on, the fan runs after a short time but the gas does not come on and ignite. The furnace obviously has power, other gas (water heater and stove/oven) appliances in my house run fine, and the gas cocks to the furnace are open.

The furnace has a Honeywell S8600M controller (97-4152 Rev. A.). I have removed, cleaned, and reinstalled the igniter, which didn't seem particularly dirty, made sure that the grounding wire from the igniter back to the controller was tight at the igniter bracket connection, and that both the hot wire to the igniter and the grounding wire back from it were well seated on their respective controller prongs. That work did nothing, however, to change the situation.

I then got my multimeter and tried to read the AC voltage being put out by the controller to the igniter (previously having confirmed that the furnace was getting ~ 120 volts AC in). In its cycling, from off to fan running but without flame, the controller output to the igniter (measured between the "9 Spark" and the "4 Gnd (Burner)" connection tabs) is ~ nil, then jumps for a short time to ~ 40 - 45 volts AC, and then drops back to ~ nil.

When connected, the igniter never sparks and I cannot tell if any gas is being fed to the igniter to light.

What further tests can I do to evaluate the situation, including determining whether I need to (1) replace the igniter; (2) the controller; (3) both; or (4) something else? Any help would be appreciated.

EBEBRATT-Ed

Sounds like no spark from the ignitor. Check the ignitor connections on both ends (maybe you have done that) and check the cable for any spots it may have rubbed on or dried out and cracked the insulation. Clean ignitor and check gap. Check ground from ignitor back to control. See the attached. It may not be the exact control you have but it is a universal replacement and all those controls are mostly the same as far a troubleshooting

Honeywell-S8610U3009-Install-Instructions.pdf

109A_5

Measuring from ground to the Spark terminal or the Spark electrode with your meter when Spark is expected is a bad idea, you may damage your meter or yourself, it is not made for that use (measuring High Voltage).

When the thermostat call for heat there should be 24 VAC between "24V GND" and "24V" terminals. Then there should be 24 VAC between "MV/PV" and "PV" and then to the Pilot valve terminals. With Pilot valve terminals energized the Spark should light the pilot. Once the Pilot flame is proven the Main Gas Valve will open. If all the 24 VAC mentioned above are present yet no Spark at the Spark electrode the High voltage wire can be tested with the Ohmmeter function of the meter. I believe the HV cable should be no higher than 1000 Ohms.