furnace help, please - PeachParts Mercedes-Benz Forum

mzsmbs · #1 10-24-2005, 11:39 PM

my pilot light on the furnace doesn't want to stay on.. i had it off all summer and now i can't get it to stay lit. the flame doesn't reach the thermal switch thingy.. i can make it stay on temporarily by putting a bit of flame to the "switch" itself but the pilot will extinguish a few moments later.. there is also a click right before coming from the gizmo where one has to depress the knob to light the pilot and then turn it to ON.. i have tried a few different times trying different ways with no luck.. any ideas?

(the proper names of parts would also be appreciated)

thanks, brrrr

Brian Carlton · #2 10-25-2005, 12:04 AM

The unit with the dial is called the regulator.

The thermal switch thingie is called a thermocouple.

What typically happens is that spiders cause the pilot tube to restrict the gas output and the flame won't reach the thermocouple. If the thermocouple doesn't sense heat from the pilot light, it shuts off the gas to the pilot light. This is so that you don't blow up your house.

So, you just get in there and remove the pilot light tube and check for spider webs. Clean it out thoroughly, reinstall it, and the flame should reach the thermocouple. After the thermocouple heats up, you can remove your finger from the override button on the regulator, and the pilot light will remain lit.

Then turn the dial on the regulator to "ON" and you'll have heat via the main burners.

Azimyth · #3 10-25-2005, 01:28 AM

Quote:

Originally Posted by Brian Carlton

The unit with the dial is called the regulator.

The thermal switch thingie is called a thermocouple.

What typically happens is that spiders cause the pilot tube to restrict the gas output and the flame won't reach the thermocouple. If the thermocouple doesn't sense heat from the pilot light, it shuts off the gas to the pilot light. This is so that you don't blow up your house.

So, you just get in there and remove the pilot light tube and check for spider webs. Clean it out thoroughly, reinstall it, and the flame should reach the thermocouple. After the thermocouple heats up, you can remove your finger from the override button on the regulator, and the pilot light will remain lit.

Then turn the dial on the regulator to "ON" and you'll have heat via the main burners.

Okay, that's it! How do you know so much about this stuff? Are you asking Jeeves?

mzsmbs · #4 10-25-2005, 01:40 AM

i think somehwere along the way he mentioned being a landlord.. or i am just confused...

BrierS · #5 10-25-2005, 08:50 AM

Quote:

Originally Posted by mzsmbs

i think somehwere along the way he mentioned being a landlord.. or i am just confused...

I don't think you are confused . . . I also would guess his educational/professional backgrounds provide him a level of understanding on "how things work". I wish Brian lived nearer NH when the MB projects are underway.

Brian Carlton · #6 10-25-2005, 10:25 AM

Quote:

Originally Posted by mzsmbs

i think somehwere along the way he mentioned being a landlord.. or i am just confused...

Yeah, I had a bunch of houses for awhile. Many of them had hot water heaters and gas furnaces that needed a bit of help at one time or another. Had to figure it out. Certainly can't call a heating contractor and give him $200. for the visit.

My greatest accomplishment was to remove a gas furnace from one of them, prepare a new proper concrete plinth, install a brand new furnace, have the the new ducts made up, and add all wiring, gas lines, and exhaust (PVC) lines.

Total cost for the job, including the furnace, and all parts was $850.00.

A heating contractor would have got $3K for the job, and he would not have done the concrete plinth nor would he have run a new thermostat line.

It took two full weekends to get it all done, but, the satisfaction of throwing the switch and watching three main burners light off was immense.

raymr · #7 10-25-2005, 12:59 PM

Not to be funny, but anyone who doesn't know what the thingy is called, is best advised to get a licensed contractor to assess the problem. Every winter season has reports of houses blowing up from leaking or faulty gas furnaces, so why risk it to save the expense of a service call? Also, a new high efficiency unit with electronic ignition will probably save you a bundle in gas bills if your current system is more than 10-15 years old.

raymr · #8 10-25-2005, 12:04 AM

Try it a few more times. It might take a while to get the 'stale' gas out of the pipe. If its still no good, either the pilot is crudded up, or the control unit is bad. Either way I would leave it to a pro to service.

mzsmbs · #9 10-25-2005, 12:17 AM

thanks guys.. i took the thermocouple off and blew crud out and lit the furnace "manually" and let it heat up the house a bit.. now i notice "scaly" material on the burners that must have falllen from above.. hmmm? the pilot still does not work unless i use my lighter to heat up the thermocouple.. i may bend the deflector shield a bit to direct the flame closer to the thermocouple..

are thermocouples ready available? cost?

i understand your comment about hiring a pro but i feel it's probably the thermocouple and i hate to drop a $100 or more for such a little part.. looks like i should be able to exchange that myself... the crud thing worries me a bit though.

Brian Carlton · #10 10-25-2005, 12:32 AM

It sounds like the pilot light is the problem, not the thermocouple. If the pilot light reaches the thermocouple, then the system will function properly. You can adjust the position of the thermocouple to ensure that it is in the pilot flame. But, if you have NO pilot flame, then a new thermocouple can't help you.

Sometimes the regulators have an adjustment for the size of the pilot flame............sometimes not.