HVAC

Have HVAC questions? Ask an HVAC Expert for answers

Ask an Expert,
Get an Answer ASAP!

My lennox heater is not heating. The thermostat is set. I…

Customer Question
My lennox heater is...

My lennox heater is not heating.

Contractor's Assistant: Did you double-check the thermostat's settings? And what about the filters?

The thermostat is set. I did not check the filter, but it is only 10 months old and the fan is running, when I just trun on the fan

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

Not sure yet

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

I can hear noise from the unit when it should be firing up. The LED indicator on the side is not showing anything

Submitted: 8 months ago.Category: HVAC
Show More
Show Less
Ask Your Own HVAC Question
Customer reply replied 8 months ago
model is C33-44C-2-6
Customer reply replied 8 months ago
led is blinking three times which means pressure switch is open with inducer on
Answered in 1 hour by:
11/16/2017
HVAC Technician: airheatman, HVAC Technician replied 8 months ago
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 9,174
Experience: Furnace, A/C and heat pump specialist.
Verified

These furnaces are what is known as a "condensing" furnace which means they actually condense water from the burning process and must be properly drained.

There are hoses in the furnace and a drain going outside.The slightest amount of debris or standing water in the main drain or one of those hoses will effect the vacuum on the switch.Also the slightest blockage in intake or exhaust will effect the vacuum.I have seen as minor as a spider wed in one of the vents cause this. Then add to that ,most of these pressure switches we get are imported from either China or Mexico and not unusual to get a bad one that sticks open or closed.

First make sure there is no water standing in the hoses

Ask Your Own HVAC Question
Customer reply replied 8 months ago
I don't see any water being blocked. The intake and exhaust are pvcs.
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

If inducer is running , no water backed up in hoses and vent clear, sounds like a bad pressure switch.

Next I want you to locate the pressure switch. It will be a small round canister with a hose attaching it to the inducer housing. Remove hose from inducer housing and leave it attached to the pressure switch. Power off and back on to reset board again, Then call for heat at thermostat. Allow inducer to start then suck on the end of hose still attached to pressure switch and see if switch will close and burners ignite.

Pressure switch may be metal or plastic, See below

http://i.imgur.com/xz4NcnM.jpg

http://i.imgur.com/at2Z27r.jpg

Ask Your Own HVAC Question
HVAC Technician: airheatman, HVAC Technician replied 8 months ago

Remove top panel and send a pic inside of furnace

Ask Your Own HVAC Question
Was this answer helpful?

How JustAnswer works

step-image
Describe your issueThe assistant will guide you
step-image
Chat 1:1 with a hvac technicianLicensed Experts are available 24/7
step-image
100% satisfaction guaranteeGet all the answers you need
Ask Phil Your Own Question
Phil
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7,426
7,426 Satisfied Customers
Experience: Retired HVAC/ Electrical & Boiler contractor. Industrial

Phil is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

You did one super job of explaining to me everything there is to know about this fridge. I'm looking forward to asking you questions in the future.

JimmyBagley, IA

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

< Previous | Next >

Meet the Experts:

Phil

Phil

Mechanical Engineer

7,426 satisfied customers

Retired HVAC/ Electrical & Boiler contractor. Industrial

Rick Mather

Rick Mather

HVAC Technician

3,133 satisfied customers

35 years experience, HVAC

Matthew

Matthew

HVAC Technician

2,014 satisfied customers

14 years experience in the HVAC field of service, installation, Manual J & D calculations

Brian HVAC Guy

Brian HVAC Guy

HVAC Technician

1,019 satisfied customers

I have been an HVAC/R mechanic/technician for 30+ years.

Kenton Guidry

Kenton Guidry

HVAC Technician

963 satisfied customers

12 years install/service experience.

Rick Ridley

Rick Ridley

UK Heating Engineer

871 satisfied customers

Retired But have had 30 years on the tools, Ex CORGI

Tom

Tom

HVAC Technician

770 satisfied customers

16+yrs HVAC/R service. Residential Commerical Industrial

< Previous | Next >

Related HVAC Questions
I have a lennox G43UF-36B-070-08 furnace and the fan is
I have a lennox G43UF-36B-070-08 furnace and the fan is constantly running but it is not blowing any heat … read more
airheatman
airheatman
HVAC Technician
9,174 satisfied customers
I have a Plus 90 i that is not heating. The fan works and
Hello, I have a Bryant Plus 90 i that is not heating. The fan works and the fuse in my house to the furnace is on. I opened the panel and saw little green, yellow and red lights to the right side. The… read more
Phil
Phil
Mechanical Engineer
7,426 satisfied customers
I have Lenox C33-44C-2F gas furnace. When heat is called,
I have Lenox C33-44C-2F gas furnace. When heat is called, one of two diagnostics light goes off. 2nd diagnostic light flashes slowly. Here are the LED flashing codes: A: Pressure switch open; B: Block… read more
Billy
Billy
Journeyman Service Technician
State Licensed Mechanical Contractor
9,330 satisfied customers
have a lennox el296uhv with a flashihg red light it flashes
have a lennox el296uhv with a flashihg red light it flashes 4 times and pauses.air filter was very dirty...have changed with proper air filter but light still flashing 4 times then a pause....is somet… read more
airheatman
airheatman
HVAC Technician
9,174 satisfied customers
I have a concern with my heater, Trane XL 80. This morning
I have a concern with my heater, Trane XL 80. This morning I woke up to a freezing house but the fan on my furnace was spinning. From the switch to the heater I removed power for about 30 seconds then… read more
airheatman
airheatman
HVAC Technician
9,174 satisfied customers
I have a c33-38b-2f-6 Lennox furnace. No heat. Red light
I have a c33-38b-2f-6 Lennox furnace. No heat. Red light flashes 3 times which the guide tells me indicates "Pressure switch open with inducer on" No idea what that means.… read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
I have a Lennox c33-36c-2f-4 heater. The red light is blinking
I have a Lennox c33-36c-2f-4 heater. The red light is blinking and the green light is on. I don't see any fire. I changed the filters and still the heater doesn't work. I turned it off and back on as … read more
Phil
Phil
Mechanical Engineer
7,426 satisfied customers
Hello. I have a ducane mpga100b3b furnace that will not fire.
Hello. I have a ducane mpga100b3b furnace that will not fire. The led light is showing 3 flashes which indicates Taft pressure switch is stuck open closed. The inducer fan does not turn on at all. You… read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
Heater not working. Installed new circuit board over summer
Heater not working. Installed new circuit board over summer because board had died for A/C, heating worked then when I tested it, and now not working. The fault code says pressure switch open. Unit is… read more
airheatman
airheatman
HVAC Technician
9,174 satisfied customers
I have a Lennox c33-38b-2f furnace which wont fire up. I
I have a Lennox c33-38b-2f furnace which won't fire up. I know the gas line to the unit is good and providing gas. Unit runs through the fire up sequence for about 3 minutes or so, then gives up. The … read more
hvac-technician
hvac-technician
Service Manager
Vocational, Technical or Trade Scho
62 satisfied customers
I have a York TG9S100C16MP11A. It worked fine this morning
I have a York TG9S100C16MP11A. It worked fine this morning now it is 5 deg below the set value and will not come on. What it is doing is cycling some fan on (not the main blower) for about 1 to 2 minu… read more
airheatman
airheatman
HVAC Technician
9,174 satisfied customers
My Lennox heater quit working at 4 am this morning. The outside
My Lennox heater quit working at 4 am this morning. The outside temperature was around 10 and it is now 21 degrees. The model # XXXXX XXXXX and it is 5 years old. It was converted at that time to prop… read more
Regan Land
Regan Land
General Manager
Vocational, Technical or Trade Scho
508 satisfied customers
My Lennox system will purge but not fire.. Problem has been
My Lennox system will purge but not fire.. Problem has been worked 6 times but is still occurring. Service Company is Ace Heating and Air Cond. in Fairfax VA. Model number is XXXXX 61MPZ36C090.. I'm c… read more
M Oglesby
M Oglesby
Vocational, Technical or Trade Scho
2,010 satisfied customers
Turned the heat on the first time today and it wont run. The
Turned the heat on the first time today and it won't run. The fan works when set to on. Model is lennox c33-43c-2f-3. Troubleshooting lights are red - off and green blinking.… read more
M Oglesby
M Oglesby
Vocational, Technical or Trade Scho
2,010 satisfied customers
Just turned the heat on for the season-- Blower motor comes
Just turned the heat on for the season-- Blower motor comes on but no heat- Can't hear burners coming on first--Just blower which shouldn't come on till after burners heat up-- Changed batteries in Th… read more
Bart Jay
Bart Jay
Vocational, Technical or Trade Scho
596 satisfied customers
My model gmph075-4 goodman heater is not working properly.
My model gmph075-4 goodman heater is not working properly. When the thermostat tells it to come on a small fan motor comes on but the burner never lights and the starter doesnt glow. There is a small … read more
Bill P.
Bill P.
Installer/ Troubleshooter/Technician
286 satisfied customers
I have a 4 year old furnace with a lennox 78m4701 circuit
I have a 4 year old furnace with a lennox 78m4701 circuit board. The heater will start up and run for about 5 minutes (fast blinking red and green then red goes out and the green fast flashes) then tu… read more
Regan Land
Regan Land
General Manager
Vocational, Technical or Trade Scho
508 satisfied customers
i have a gms81155cna heating unit. it keeps blowing the 3 amp
i have a gms81155cna heating unit. it keeps blowing the 3 amp fuse. when replaced it runs but reoccurs allmost immed. i dont get any diognostic flashing what could be causing it.… read more
M Oglesby
M Oglesby
Vocational, Technical or Trade Scho
2,010 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x