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Having problems with my furnace. have replaced the pressure…

Customer Question
Having problems with my...

Having problems with my furnace. have replaced the pressure sensor, the electric ignitor, and the thermostat, but it still wants to cycle on and off.

Contractor's Assistant: Just to clarify, do you think this is a larger HVAC problem, or something specific to the thermostat?

I!m not sure. had the gas pressure checked and a service person look at it, but no solution was made.

Contractor's Assistant: Do you plan on doing the work yourself?

I F I CAN, AND IF ISNT TO COMPLICATED.

Contractor's Assistant: Anything else we should know to help you best?

WHAT IS YOUR RECOMENDATION?

Submitted: 11 months ago.Category: HVAC
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Answered in 1 minute by:
10/1/2017
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago
Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 24,845
Experience: 40+ yrs. experience as a licensed oil & gas technician.
Verified

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. First I’ll need some more info so I have a more complete picture of your situation. WHat is the brand and model number of your unit?

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Customer reply replied 11 months ago
carrier weathermaker 8000
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

What do you get for an error flash code on the control baord LED when the unit fails?

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Customer reply replied 11 months ago
I, HAVENT CHECKED THAT. THE FURNAC IS A CARRIER WEATHMAKER 8000.
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

I can't help you if you can't tell me what error the control board is displaying. The brand and series (Weather maker 8000 is not the model) doesn't help.

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Customer reply replied 11 months ago
OK, I!LL LOOK FOR THE MODEL # ONE MOMENT PLEASE.
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

I need the flash code. I can't help you without it

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Customer reply replied 11 months ago
CAN!T SEEM TO FIND A MODEL #.WHERE MIGHT IT BE?
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

The model number is ***** for now. I need the LED flash sequence. How many long and short flashes?

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Customer reply replied 11 months ago
OK, YOU CAUGHT ME OFF GUARD. LET ME TRY AND START THE FURNACE. IS THE INDICATOR LIGHT ON THE CONTROL BOARD?
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

Yes, you should be able to see it through the peep hole in the blower compartment access panel. Don't remove the panel. That erases the code.

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Customer reply replied 11 months ago
OK STANDBY.
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

ok

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Customer reply replied 11 months ago
NEVER SAW ANY BLING LIGHT.THERE IS A RED LIGHT THAT STAYS ON ALL THE TIME . PROBLEY A POWER INDICATOR.
Customer reply replied 11 months ago
RAN THE UNIT A FULL CYCLE BUT NO LED BLINKING LIGHT.
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

If the LED doesn't blink there and it ran for a full cycle what's the problem?

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Customer reply replied 11 months ago
O.K THE PROBLEM IS THAT THE UNIT WANTS TO START SHORTLY AFTER THE FURNACE HAS FINISHED RUNNING. THE GAS COMES ON AND IGNITES FOR ABOUT 15 SECONDS AND GOES OFF. THE FAN WILL RUN FOR ABOUT 2 MINUTES, AND THEN TURN OFF. THIS HAPPENS TILL I TURN THE STAT DOWN.
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

Is the thermostat satisfied when it initially shuts down?

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Customer reply replied 11 months ago
THE UNIT WILL RUN GOOD THE FIRST TIME , B UT WILL CYCLE ON AND OFF AFTER THAT
HVAC Technician: Rick, HVAC Supervisor replied 11 months ago

I'm going to open this up to my colleagues so one of them can help. Please don't respond (even to acknowledge this post)until you get a response from us. If you respond first it will only delay your answer.

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Customer reply replied 11 months ago
I WOULD ASSUME THAT THE STAT IS SATISFIED.
HVAC Technician: Michael Ferryman,
 replied 11 months ago
Michael Ferryman
Category: HVAC
Satisfied Customers: 110
Experience: Operating Engineer at NRG Energy
Verified

You need to replace your thermostat, its causing your unit to short cycle.

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HVAC Technician: Michael LaMott,
 replied 11 months ago
Michael LaMott
Category: HVAC
Satisfied Customers: 1
Experience: HVAC System Designer at Icon Air
Verified

Hi. My name is ***** ***** I may be able to help.

The problem may be a dirty flame sensor.

Was the furnace working fine previously and then started short cycling?

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HVAC Technician: HVAC Guru,
 replied 11 months ago
HVAC Guru
Category: HVAC
Satisfied Customers: 37,996
Verified
Phone call session started
Customer reply replied 11 months ago
thank you for you response. i again checked the led light and it was a short and long and short blink. does that help any?it did it again as i watched it. i found the flame sensor. could that be the problem?
Customer reply replied 11 months ago
the furnace had been working previously, then started cycling on and off.
Customer reply replied 11 months ago
cleaned the flame sensor with fine sandpaper,as suggested. ran furnace thru a cycle. after about ten minuets, it tryied to run again, but did not do so. led light blinks one long and one short,then one long. hope i viewed it right.
Customer reply replied 11 months ago
thermostat is new.the pressure switch is new. the ignitor is new. cleaned the flame sensor. what next?
Customer reply replied 11 months ago
also has new filter. ran great for the last 5 years till now.
HVAC Technician: Michael Ferryman,
 replied 11 months ago
Unfortunately it sounds like are have a issue with the heat strips on the unit... when the unit shuts off how are you resetting it?
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HVAC Technician: Michael LaMott,
 replied 11 months ago

If you have a multimeter that reads microamps DC, you can check the flame sensor and see if you get a min of .5 microamps dc. Normal should be around 4.0 to 6.0 for your furnace. Check by simply disconnecting the wire to the sensor, and use the meter leads in series (one lead on the sensor terminal and one lead on the disconnected wire...

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Customer reply replied 11 months ago
would it be wise just to buy a new flame sensor? by replacing the flame sensor, and the furnace still does the same thing, what then?
HVAC Technician: Michael LaMott,
 replied 11 months ago

I really don't like replacing parts until we check them out- if possible.

I am thinking the flame sensor could still be the problem or it may be the pri***** *****mit switch.

The flashing code you saw doesn't indicate a problem. If it were flashing more than once, it would indicate a problem.

Have you noticed any other codes since you last posted?

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Customer reply replied 11 months ago
where is the pri***** *****mit switch? how would i check it? i shut the stat down after the first cycle, so it does not start to try and come on and off.
Customer reply replied 11 months ago
have not checked any more codes.
HVAC Technician: Michael LaMott,
 replied 11 months ago

The pri***** *****mit is located behind the burners and the gas valve. It has 2 wires going to it. It is attached to the sheet metal panel with 2 screws.

You can bypass it (TEMPORARILY FOR TESTING ONLY) by disconnecting the wires and connecting those 2 wires together...

If the furnace works and does not shut down, That switch may be the culprit.

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Customer reply replied 11 months ago
ok i will try it tomarrow.
HVAC Technician: Michael LaMott,
 replied 11 months ago

Any luck with this?

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HVAC Technician: Michael Ferryman,
 replied 11 months ago
Did you need any further assistance with this? If not can you give me a 5 star rating. Would really help me out. Thanks so much.
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