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Posted: 1/8/2005 6:08:24 PM EDT
I have a Janitrol gas furnace, LP, and it's running but the burners only light for 5 seconds or so, then shut off.

I've metered all the limit switches, and jumped across them to rule that out, no luck. Shut down the breaker first to clear the electronics just in case, etc.

The pressure valve is working, tested it on the meter too (suck in/blow out, test for open/closed switch).

The blower motor is kicking on, and everything looks like it should work but still no luck.

I'm a relative newbie to furnace repair, so I'm thinking gas pressure is weak. Dunno what else to try, any suggestions?
Link Posted: 1/8/2005 6:13:58 PM EDT
check the rollout sensor.
Link Posted: 1/8/2005 6:15:46 PM EDT
flame sensor
A small round rod and one end of the burners w/ a single wire attached to it.
Usually orange in color.

Now send my prize.
Link Posted: 1/8/2005 6:18:39 PM EDT

Originally Posted By ARs4EVER:
flame sensor
A small round rod and one end of the burners w/ a single wire attached to it.
Usually orange in color.

Now send my prize.



If that ends up being it, I'll do just that!
Link Posted: 1/8/2005 6:22:58 PM EDT
No way to bypass that part. If its under 5 years old parts are free.

Rick
Link Posted: 1/8/2005 6:30:03 PM EDT
Thermo-coupler, take a piece of emry cloth and polish it.
Link Posted: 1/8/2005 6:40:15 PM EDT

Originally Posted By 1shott:
Thermo-coupler, take a piece of emry cloth and polish it.



I don't think it has a thermocouple. These have either a hot surface ignitor or spark ignition.
No need for a standing pilot. Thats old stuff.

Rick
Link Posted: 1/8/2005 7:31:14 PM EDT

Originally Posted By ARs4EVER:

Originally Posted By 1shott:
Thermo-coupler, take a piece of emry cloth and polish it.



I don't think it has a thermocouple. These have either a hot surface ignitor or spark ignition.
No need for a standing pilot. Thats old stuff.

Rick



Correctomundo, no thermocoupler.....and drum roll please....

It was the flame sensor. Took it out, cleaned it with some 0000 steel wool and that did the trick. Flame has been constant and furnace is cycling normaly.

You da man! If I had a hot sister, I'd let ya slip it to her.
Link Posted: 1/8/2005 7:49:23 PM EDT
I would still get a new flame sensor. I really don't know what makes them go bad but I do change a few each year.
The sensor when subjected to heat, makes millivolt.

Since the sister is out of the question WHERE's MY PRIZE?

Rick
Link Posted: 1/8/2005 7:58:32 PM EDT

Originally Posted By ARs4EVER:
I would still get a new flame sensor. I really don't know what makes them go bad but I do change a few each year.
The sensor when subjected to heat, makes millivolt.

Since the sister is out of the question WHERE's MY PRIZE?

Rick



Yeah, I figured I'd change it, cheap part anyway. But, I wanted to suss out the problem and that worked. Dunno how I didn't think of it, but thank you.

Howzabout I send ya a good beer? What's your brand?
Link Posted: 1/8/2005 8:08:14 PM EDT
Link Posted: 1/8/2005 10:30:23 PM EDT
I have to do the clean the flame sensor trick every year or so. Its not bad. I asked a guy was a HVAC tech the same question and his first reply was to ask if I had a water softener near the furnace. Yup, in the same small utility room. He claimed it had to do with the salt of the softener somehow. I dont know  but as soon as I hear it take more than once to ignite and run in the same start cycle I pull it and clean it with scotchbrite.
Im curious if you have a water softener as well??
Link Posted: 1/9/2005 2:19:12 AM EDT

Originally Posted By ARs4EVER:

Originally Posted By 1shott:
Thermo-coupler, take a piece of emry cloth and polish it.



I don't think it has a thermocouple. These have either a hot surface ignitor or spark ignition.
No need for a standing pilot. Thats old stuff.

Rick



Well I hate to tell you this, BUT my furnace is one of them new fangled funraces, with out a standing pilot, and yes it has a thermo-coupler.  That is the part you cleaned,  you see, if your thermo-coupler does not register a constant flame, your furnace willl not stay lite, it will shut down and close off the gas valve, since it is not  registering heat.

I also have to clean the thrmo-couplers on the flame treaters at work.

Link Posted: 1/9/2005 6:59:54 AM EDT

Originally Posted By tnek:
Im curious if you have a water softener as well??



Yes, I do, but it's not close to the furnace. Probably 30 feet away.
Link Posted: 1/9/2005 7:14:30 AM EDT

Originally Posted By ARs4EVER:
I would still get a new flame sensor. I really don't know what makes them go bad but I do change a few each year.
The sensor when subjected to heat, makes millivolt.

Since the sister is out of the question WHERE's MY PRIZE?

Rick



No the flame sensor transmitts dc volage in millivolts to ground through the flame, due to enough unburned hydroCARBONS left in the flame. The electrons pass from carbon molecule to molecule to ground, the module measuress this electron fllow and says..."Yes we have flame, carry on".
When the buildup of crud gets on the sensor it acts like a corroded battery terminal on your car battery.

Railgun....
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