'03 Lennox (50A65-121-06) stumped the pros. Need suggestions

[the_heat_is_on]

Lennox/Surefire/White Rodgers 50A65-121-06 controller.
It has an 80V Silicon Nitride hot surface igniter

My Lennox heater crapped out - holiday very cold days.
Was working intermittently, now almost never.

Lights blink controller indicating it could be one of:

--Bad grounding
--Low voltage
--Bad igniter (however, igniter glows every time and tests at 19ohm, within spec)

Igniter glows every time. But when usually controller blinks after it's been glowing a few
seconds and won't turn on gas.

Sometimes after powering it off for awhile and powering it on it starts.
Sometimes it seems like it does after I jiggle the base of the igniter, but
that doesn't always work and may not be related at all.

I called HVAC company to diagnose. First guy blamed it on a power surge
powered it up once, he left telling me I'm in good shape. 1/2 hour later
stopped coming on and continued to get worse. Once it starts cycling
seems to need a power reset, but even that doesn't guarantee it will
start. Usually doesn't.

Called, 2nd guy came out, did electrical checks
and was stumped. All in all they checked gas pressure, gaskets, voltages,
resistance, grounding connections, but he couldn't check milliamp flow
as he said he didn't have the right type of meter.

I've started a DIY approach (getting igniter, and then maybe board if needed),
as I don't want to gamble and waste time with guesses and we need heat ASAP.

I'm also interested in understanding how igniters fail (various failure modes)
and how boards tend to fail, and if there's ever a case people repair them (
open and clean a relay or replace a relay), etc...

[kdean1]

Your DIY approach can lead to disaster. Find a better service company.

This site has a rigid NO DIY policy.