Furnace Ignitor Intermittently Fails To Energize

[Tony Hwang]

Hi, They seem to use non usual nomenclature for parts. item #16 on IPB(illustrated parts breakdown) called air tube. Can you locate it?

[notbob]

Funny this thread came up. My central forced heater jes failed. The heater had been running for 20 mins and the room temp kept dropping. I had half a tank of propane (250 gal) and the oven worked fine. Must be that danged spark gap igniter.

It was not the spark gap igniter being literally burnt off at the stubb, like I've seen before. The problem was "whiskers" forming on the igniter tips and shorting the two electrodes out, intermittently. I pulled the igniter (4 screws) and cleaned the "whiskers" off and put it back together. It works, now, but I suspect those whiskers will continue to rapidly form on the now corroded electrode tips. Probably will until I put in that new igniter.

BTW, my 3 'trode igniter cost $39, not the "less than" $20 I quoted before.

nb

[mfreshny]

Hi Mark,

I don't believe there is a pressure sensor in this model. There's no mention of one in the manual or the parts list, and I don't see one visually.

What it does have are a few relays, that supposed to tell the other components to turn on... I'm now thinking that one if these relays are faulty, and maybe the S89 cntrl module isn't getting power ... the relay is a cheap part, $15 bucks online.

i'm thinking now - when it fails to use a voltometer on the s89 to see if it gets any power at all.

Am I on the right track here ?

[mfreshny]

Tony, that's not my model - check page 5, direct ignition gas burners for power gas models..

There are 2 relays left out of the diagram - in the electric box , the time delay relay and the motor relay .

[Tony Hwang]

Hi, They call it pressure switch. Try Googling Nordyne furnace pressure switch. Any thing like that around inducer motor? The switch is NO type. Closes when pressure is sensed. It can get stuck open or closed.

[mfreshny]

I 'm reading up on the "centrifugal relay", - it looks like it serves the same purpose as the pressure sensor- and it's at the base of the inducer motor, inside.

I don't think it's a servicable part, it might be part of the motor, which would mean replacement.

Still taking suggestions!

[Tony Hwang]

Hi, If that is the case it is very poor design. Motor turning can't guarantee right pressure. What if turbine is loose on the motor shaft? Cenrifugal relay is not really a relay(coil. actuator, contacts) it is just a contacts which closes when motor spins up to full speed against a spring tension. Contacts can burn or get pitted making poor contacts causing intermittent problem. You can burnish the contacts some times to make it work again.

[Ralph Mowery]

It all depends on the motor. I just replaced a similar part on my well pump motor. It is a set of contacts that puts a capacitor in line with the motor to start it. Just a couple of screws and push on terminals.

[mfreshny]

I was able to get the cover off the motor, exposing the centrifugal switch. ..it looks brand new and clean inside - I blew some canned air into it, cle aned the contacts, put a few drops of oil on the shaft, then closed it up and oiled the front end through the oil holes. Motor is quieter but still the same problem!

[bob_villa]

h...it looks brand new and clean inside - I blew some canned air into it, c leaned the contacts, put a few drops of oil on the shaft, then closed it u p and oiled the front end through the oil holes. Motor is quieter but stil l the same problem!

If this is a 2-wire (W/Grnd) motor, then it's just for a start winding.

[Stormin Mormon]

exposing the centrifugal switch...it looks brand new and clean inside - I blew some canned air into it, cleaned the contacts, put a few drops of oil on the shaft, then closed it up and oiled the front end through the oil holes. Motor is quieter but still the same problem!

You now have one more repair that is known to NOT fix your furnace.

- . Christopher A. Young learn more about Jesus .

. .

[mfreshny]

ducer motor comes on, the ignitor glows. After about a minute the gas ignit es and then blower comes on.

otor keeps running. Turning the furnace off and on, either by the thermosta t or the door restarts the furnace, no problem. There's no pattern to it - it'll go for a week just fine, then 2 days in a row it fails...The problem seems to be getting worse tho, needing more resets since I first noticed la st winter.

ins. Could it be an intermittent problem with the Ignition Control Module not sending power to the ignitor? It's a older model Honeywell S89C1087, no LED.

SOLVED !!!

Just an update: I limped through last year, didn't want to start messing ar ound with it too much when the temp was -25. This fall replaced the Igniti on Control Module s8910u1000, 75 bucks at Amazon and an hour of time.... Ss o far so good, has always come on!

Thanks for all the feedback!