Hvac

[fabricator]

Who is the heat and air guru
I have a rheem classic 90 about 4 years old
started in the spring thought it was low on propane
but is still doing it this fall
will cycle and heat like it should then cycle off
next time it will cycle blower will kick on
cycle back off b/4 it should, kinda like it runs out o propane ?
will cycle on off on off on off several times
without lighting, will go in shutdown mode... I guess is what it would be called
10- 15 minutes later will go thru the same ****
sometimes it will light and run sometimes it wont

thermostat cause this?
HELP..

[wilson1010]

thermocouple

[JeffK5]

thermocouple

Bingo!

Had my NG furnace do the same thing ....

[fabricator]

thremowho?
these hard to replace ?
where to buy?
guess i need model # and name of furnace
cost much?

[itbrokeagain]

616 5750 Mike sawyer.

[carwash]

same thing happened to ours this past spring to end the season. replaced the whole thing... not sure if the thermocouple is hard or expensive, we just needed a new furnace and didnt want to dump any money into the old one.

[JeffK5]

A thermocouple is nothing more than temp. probe that sends info to the "brain" in your furnace.

When it acts up it gives the units controller bogus information , the problem my furnace had was it thought the fire on the burner failed to light so it shut the gas off ...even though the fire was burning as it should.

Turns out the thermocouple had shorted internally and was not sensing any heat ... no signal from the TC to tell it "successful ignition" so it shuts down.

Cheap and easy!

[nick]

your furnace should have a flashing light on the control board count the number of blink through the door do not take blower door off it will reset the board and you will have to wait for it to do it again on the door somewhere there should be a list of numbers that will give you the definition of what the blinks mean.. a 90% furnace does not have a thermo couple it has a flame sensor my guess is the furnace is getting to hot check your filters

[RuffedUpXJ]

Mine actually started acting up and it was due to the pressure switch which tells the control board the exhaust fan for the fumes is working. I did read my basically CEL on the board and thats what came up and I jumped it for now so the control board believes the switch is sensing the exhaust fan is working but Monday I am getting the switch so I don't need to jump it every time I want to heat my house it.

Basically the way your furnace will work is the exhaust fan will turn on first and it hopefully works and then the pressure switch tells the board everything is good. Then the hot surface igniter kicks on and glows. Then the gas control valve kicks on and starts the gas flow which goes through your plenums. The gas is ignited and the flame sensor send a voltage to the control board saying there is a flame. Sometimes the FS goes bad and you need to replace it ($30). So mine would cycle and start and reach a flame but after about 5 seconds of igniting the gas it would kick of because the exhaust weren't be sensed as leaving the chamber. But there should be a little plastic lens so you can see your control board with the lower cover on. Once it messes up and doesn't continue to run watch to see if the LED blinks. If it does take the cover off and read the panel which should tell you what might be wrong.

Hopefully that helps a little.

[itbrokeagain]

Little trick. Take some fine grit sand paper to the flame sensing rod. These get all carboned up and dont sense the heat properly. On a 90% Rheem Im guessing its a spark ignition and if its like the waterheaters, the spark ignitor is also the flame sensor.

[fabricator]

took the covers off
kinda dusty, 1 filter wasnt put in correctly
since i cleaned them last...what a dumb ass
anyway vacuumed the area
found what appears to be a round springy switch thing
about the size of a quarter
cleaned it real good wiped it off with finger
wiped something else down... inch or two long
about 1/4 inch round
anyway ducked the safety switch down
like anyone would and fired it up
went thru a cycle just fine
12 hours later
is still working fine
hopefully it is fixed
thanks guys

[pete]

did anyone fess up that they were a hvac guy. I need a furnace installed.have the furnace just dont have duct work yet. let me know if anybody does this cheap lol thanks pete

[itbrokeagain]

did anyone fess up that they were a hvac guy. I need a furnace installed.have the furnace just dont have duct work yet. let me know if anybody does this cheap lol thanks pete

616 5750 Mike sawyer.

:)

[fabricator]

yep, seems to still be still working
the way it should

[fabricator]

furnace isn't fixed, it is just messin with my head
well at least it's not periodic, doesn't work at all now
took what appears to be the flame sensor out
sanded, put it back in.
has LED's... flashes 4 times then starts what i think is a new cycle
doesn't even get to the ignition stage at all
pressure switch maybe.
looks like the yellow pages on this
not sure what else to do here
Called the # above but hate 2 keep aggrivating to guy
is a far drive for him