spark ignited furnace question

I've noticed recently on my spark-ignitied (not standing pilot) Olson Mini Max furnace that the spark ignition runs a LOT longer before it stops and fires than it did before.
in the last 1.5 years here, the furnace has just "bzzzz.poof", sparking for maybe 4 or 5 seconds at most and lighting without fail. Now (internittently) the unit will spark for 15 or 20 seconds and seems to "timeout" and then light. other times it lights perfectly.
in my gas fireplace adventures, I know that there is a part in the furnace that detects the presence of flame to tell the unit that the pilot is lit (so stop sparking, and open the gas valve). what is the proper name for this part? it seems that these devices are right at the front and fairly user serviceable....
I am a handy person and really really hate to give money to a technician to do super simple repairs....
any ideas?
b
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Hamilton Audio wrote:

It's called "flame rectification". (Do a GOOGLE.)
Some systems use the same electrode for both the spark and the flame detection; others use a separate probe. If the probe is dirty or the plating gone, proper detection will be sporadic. You can try cleaning it or replacing. That part should be available.
Jim
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I see the sparker with a large orange cable running to it. being the cold season, the furnace is running reasonably often....so she's too hot to touch right now and take a peek ;)
I will, however, disassemble tomorrow when its cool and take a closer look. i've got a handy furnace power interupter switch right on the wall.....so I can simply crank the tstat and stop the furnace from firing with the switch. take apart, clean, and test fire without having to go all the way back upstairs (heheh). sounds like a plan to me!
if cleaning the flame detection probe cleaning doesn't yeild improvement - where do you think I can prodcure an additional one? also, what about an installation/assembly manual for this furnace so I can see how it comes apart??
thanks for the help!
b

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Hamilton Audio wrote:

You'd have to find the mfr of the ignition control; probably made by a major controls co., not MiniMax.

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Hamilton Audio wrote:

Are you saying that the spark DOES light the pilot but the spark keeps going, or are you saying that the spark FAILS to light the pilot and the spark keeps going?
Mark
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the spark ALWAYS lights the pilot and sets the furnace going (has never /not/ lit)....its that sometimes the pilot lights and the spark keeps going (situation 1 above).
b
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