Ignitor Flash Code Question

Doc Holliday

Service call on a Lennox furnace something or another, the model number is out in the truck.

No heat and according to legend, normal simultaneous fast continuous flashes (dual l.e.d.) while on call for heat. Inducer on, ps closes and no ignitor. Voltage to ignitor present, no ignition.

I'm replacing the ignitor tomorrow but the question is why isn't there a flash code for a failed ignitor? That and why does it flash "normal operation" if it won't light up?

Maybe I missed something on the legend?

Master of Cold

Because there is enough current passing through the ignitor for the computer to read that voltage made it through.

Think of it as a burnt contactor. You can still read voltage, but you can't get enough current through it to start the compressor.

Master of Cold

Did you give it enough tries to lock out?

Doc Holliday

I tried it about ten times. I disabled all visible safeties one at a time, two rollouts, the pressure and one temp, to see if they worked and if the code corresponded to each. All safeties worked, stat off and controlling furnace at board, cool, fan and heat.

One thing I also noticed, 34.? VOLTS at the flame sensor while on call for heat without igntion and flashing normal heat operation.

Will that go away once ignitor is replaced? Normal?

Thanks.

Master of Cold

Im the master of cold, not heat d***it.. ;-)

If you have 34 volts, something is bleeding through.

Master of Cold

How did you check voltage on the flame sensor?
Normally you would check for microamps.

Doc Holliday

At the end of the wire where it connects to senso r, before rod. I just spoke with Lennox tech support, said board will always send small AC voltage to sensor, normal. Reads back flame to ground DC Milli. That's my confusion.
Thanks.

Marty S.

The universal nitride ignitors are a good thing to have on the truck doc. Part number L41 806 at johnstones.

Doc Holliday

Marty, the Lennox ignitor is the nitride but supposedly universal won't work. I replaced $50 ignitor, same thing. It wouldn't light. Called tech support, did the stick a pin in inducer hose port and furnace lit. Both ignitors good via ohms.

Doc Holliday

Resistance range 10-19 ohms. After new installed is when I found that out. Both near 14.

how

Hey Doc
I've got a number of lennox's that won't run for two years without an inducer hose port or pressure control poke. It's gotten to the point that I now consider it a part of normal lennox maintenance and my customers with more problematic lennoxs automatically do it before calling me out on a breakdown. I think the lennox design needs more stainless steel or a few debris dumping collection spots before the choke points.

Should of still shown up on the led code???

Doc Holliday

After new ignitor and state calling heat I held door switch in until flash code changed from normal heat to one of three options, one being PS closed before inducer.

Doc Holliday

PS was open with I'd off, closed once running.

Marty S.

Yea that one should have given you a pressure switch fault if the port was blocked and you said the ps was closed. I bet the 2 prong molex connector for the hsi has a loose pin. If it happens again cut the connector out and use wire nuts.
BTW the universal nitride works fine on a lennox. The lennox control board sends 120V on the first fire and drops the voltage a percentage each call after that until the unit will not light, then it bumps back up one step. After 500 lights it starts the process all over again. That's why lennox rarely loses a hsi, I've replaced 2 out of thousands that we installed(used a universal nitride both times).

Doc Holliday

Wasn't my money.