Gas and Oil Home Heating Furnaces - Pilot on but no igntion

Hello all and thanks in advance for whatever advice you can offer.

I have a Rheem Furnace RGDA 10EC-EA that came with the house when I got it. It's equipped with HSI using a Honeywell S89G controller.

Here's the intermittent problem. Thermostat calls for heat and the igniter glows nice and hot. Typically, I hear the gas valve click on and the pilot bar gets lit, and the furnace fires up. But, every now and then (once a week more or less) I walk into a cold house or wake up in one.

The igniter will glow but the furnace won’t fire up. My fix is to shut the furnace breaker off, and thermostat. Let sit for 30-45 minutes and turn everything back on. I first thought maybe the pilot rail was dirty and I cleaned it. I’ve checked all the connections and they all seem fine. Any thoughts on a bad control unit or something else?

Mkae sure the flame sensor is clean (use steel wool) and that the pilot flame strikes it squarely. If that doesn't help, I would suspect the S89.

Ken

Have you ever seen the unit fail (does it fire and then turn off or not fire at al then lock out) before you turn it off next time look for a flashing light that will geve you a helpful failure code the code legend will be on the wiring diagram.

Mkae sure the flame sensor is clean (use steel wool) and that the pilot flame strikes it squarely. If that doesn't help, I would suspect the S89.

Ken

Forgive my ignorance but can you tell me where the flame sensor is located?

Look for the 'sense' terminal on the S89 and follow the wire back to the sensor.

Ken

Have you ever seen the unit fail (does it fire and then turn off or not fire at al then lock out) before you turn it off next time look for a flashing light that will geve you a helpful failure code the code legend will be on the wiring diagram.

I've had it fire up only to shut off before getting to temp. Is that what you're talking about. I didn't notice any flashing lights anywhere though. No LEDs on the S89G.

Look for the 'sense' terminal on the S89 and follow the wire back to the sensor.

Ken

Thanks! I will give it a try.

Thanks! I will give it a try.

Still experiencing the same symptoms. No "Sens" terminal on the S89G - a couple for the valve, ground, and a couple for the HSI. One of the HSI terms for the igniter says sensor but no other leads.

Igniter still stays on, no pilot gas. Will the igniter stay lit on lockout?

No the ignitor will not stay lit after the control determines that there was flame failure. It will recycle depending on the model of the S89. It sounds liek the control is defective. Replace the ignitor also because they don't last forever and this would be a good time to change it.

Ken

The igniter will glow but the furnace won’t fire up.

But then the thread title says: "Pilot on but no ignition".

When the furnace does NOT work, which is the real problem?

No the ignitor will not stay lit after the control determines that there was flame failure. It will recycle depending on the model of the S89. It sounds liek the control is defective. Replace the ignitor also because they don't last forever and this would be a good time to change it.

Ken

There is a new ignitor currently installed. I'm guessing the the box is bad.