HVAC

Have HVAC Questions? Ask an HVAC Expert for Answers

Ask an Expert,
Get an Answer ASAP!

HVAC

1998 Lennox, model G20Q3/4E-100-1, pilot comes on, blower

Customer Question
Hi, 1998 Lennox, model G20Q3/4E-100-1...
Hi, 1998 Lennox, model G20Q3/4E-100-1, pilot comes on, blower runs, but burner doesn't light, so no heat. Where to start?I have the same furnace with the same problem. Per your response to this question, I cleaned the probe. It made no difference. The probe does glow red hot. Does it matter what part of the flame the probe is in? I acquired the furnace used and installed it myself to replace an old gas converted oil burner. I have the Lennox User’s Information, Unit Information, and Installation Instructions manuals.I measured the flame signal going to the Robertshaw Ignition Controller. It measured in the 1 – 5 microamp range but the signal rapidly jumps around. Measured as voltage it jumped from zero to 230 microvolts. I checked the connections. Could it be a cold solder joint in the controller?The controller never brings up the MV signal. Jumping the valves MV line to the controller’s pilot signal will bring the main burner on and the furnace completes its heat on cycle.Any suggestions?Herbert ***************
Submitted: 1 year ago.Category: HVAC
Show More
Show Less
Ask Your Own HVAC Question
Answered in 7 minutes by:
11/10/2016
HVAC Technician: HVAC Guru, HVAC TECH replied 1 year ago
HVAC Guru
HVAC Guru, HVAC TECH
Category: HVAC
Satisfied Customers: 15,758
Experience: 20yrs in the HVAC industry with certificates and degrees.
Verified

Hello, one minute while I get some information together.

Ask Your Own HVAC Question
HVAC Technician: HVAC Guru, HVAC TECH replied 1 year ago

Hello and thanks for using this service! If you are a JA Member I would like to personally thank you and welcome you back! I am HVAC Guru an extremely experienced tech on the site and I try to get to as many customers as I can. NOTE it takes time for me to type research and add links so please wait for me to respond back I can only do this so fast. Secondly, I do not know your skill level so please try and let me know if I am going beyond your knowledge or comfort zone thanks! I strive for a 5 star rating from everyone especially our JA members.

Answer:

Replace the controller it is bad.

All I ask is please use the Star Rating Link at the top of your page before leaving, that is the only way I am credited through the site, tips are appreciated.

Ask Your Own HVAC Question
Customer reply replied 1 year ago
At the moment I rate the service as poor. I was pretty sure it was the controller but to me the jumping current from the coulr come from a bad connection. If the response said that is normal for the probe's output to jump around I might be more accepting to drop $200 to $400 for a new controller. I stated that funds were tight and reassuring me that one of the $100 generic units were fine. Since you are not selling anything a suggestion of the best place to buy would help up my rating.
I said that I was capable of component level repair. A wiring diagram and reassurance that some have done it would also up the rating.
Questions to answer before a rate you.
1. Does the current from the probe jump around?
I have line on a SP735P for $40. I it a direct replacement for my SP735L?
3. do you know of someone who has fixed one by touching up the cold soldering joints?
4. If I have to go for a new one what and where is the best buy and should I get a kit with a new probe?
Lastly since I signed up for a 30 day trial, do you know anything about a Honeywell F300 Electronic Air Cleaner
Customer reply replied 1 year ago
It is not clear to me that the remarks below reached you. so I am entering it in this box and resending it.11 November 2016 03:43
At the moment I rate the service as poor. I was pretty sure it was the controller but to me the jumping current from the coulr come from a bad connection. If the response said that is normal for the probe's output to jump around I might be more accepting to drop $200 to $400 for a new controller. I stated that funds were tight and reassuring me that one of the $100 generic units were fine. Since you are not selling anything a suggestion of the best place to buy would help up my rating.
I said that I was capable of component level repair. A wiring diagram and reassurance that some have done it would also up the rating.
Questions to answer before a rate you.
1. Does the current from the probe jump around?
I have line on a SP735P for $40. I it a direct replacement for my SP735L?
3. do you know of someone who has fixed one by touching up the cold soldering joints?
4. If I have to go for a new one what and where is the best buy and should I get a kit with a new probe?
Lastly since I signed up for a 30 day trial, do you know anything about a Honeywell F300 Electronic Air Cleaner
HVAC Technician: airheatman, HVAC Technician replied 1 year ago
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8,502
Experience: Furnace, A/C and heat pump specialist.
Verified

I am a different expert.Lets' back up and start fresh. Do the burners ever actually light?

Ask Your Own HVAC Question
Customer reply replied 1 year ago
If I jump the MV to PV after pilot lights main burner lights and furnace works
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

OK , let me ask this .When thermostat calls for heat, inducer comes on , then ignitor.While igniter is on check and see if you get 24v to valve.

Ask Your Own HVAC Question
Customer reply replied 1 year ago
The SP715l never supplies 24v to main valve. The probe supplies the 1-5 uamp to control but current jumps up and down rapidly. Is this or normal?
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

What probe.Are you referring to the lame sensor on pilot?

Ask Your Own HVAC Question
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

I see so pilot is lighting, just not the burners?

Ask Your Own HVAC Question
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

The 1-5 is normal as it will fluxuate.Looks like it will be the board as everything else in circuit has done as it should, board is just not getting signal.It is common for these boards to develop stress cracks.Not very many people attempt trying to trace and repair the solder joints.Best bet is to get number off of board and lets Google it to find best price on a replacement.

Ask Your Own HVAC Question
Customer reply replied 1 year ago
I have. I have a line on one for $40. Thanks.
What I didnt get from first tech was that probe output was normal.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

I understand. I never like to just throw out an answer telling someone to replace a part, especially an expensive part without doing some troubleshooting and verifying a few things.

Ask Your Own HVAC Question
Ask airheatman Your Own Question
airheatman
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8,502
8,502 Satisfied Customers
Experience: Furnace, A/C and heat pump specialist.

airheatman 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

6,730 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

Kenton Guidry

Kenton Guidry

HVAC Technician

963 satisfied customers

12 years install/service experience.

Brian HVAC Guy

Brian HVAC Guy

HVAC Technician

953 satisfied customers

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

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 an oil burner question, One week, Yes, Please connect
Please connect me with someone who deals with oil burner questions… read more
Billy
Billy
Journeyman Service Technician
State Licensed Mechanical Contractor
9,330 satisfied customers
Riello 40 series mectron oil burner has issues on cold
Riello 40 series mectron oil burner has issues on cold start … read more
Brian
Brian
Plumbing & Heating Engineer
116 satisfied customers
I Have an old Peerless oil burner with a Aquastat-Protecto
i Have an old Peerless oil burner with a Aquastat-Protecto Relay Unit Type R8182D. … read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
I have an old Vaillant oil burner and I was told the "Gun"
I have an old Vaillant oil burner and I was told the "Gun" is gone … read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
I have an international oil burner company mac 1199 and the
I have an international oil burner company mac 1199 and the blower will not cycle off. I can flip the switch to shut it off, but it wont shut off on its own when it reaches temperature. The thermostat… read more
Billy
Billy
Journeyman Service Technician
State Licensed Mechanical Contractor
9,330 satisfied customers
I have a 2 zone house with an oil burner, 2 air handlers and
Hi, I have a 2 zone house with an oil burner, 2 air handlers and 2 AC units. The system is connected to a Taco SR 503 zone controller, with zone 1 being the water storage tank, zone 2 being downstairs… read more
Michael Ferryman
Michael Ferryman
82 satisfied customers
My oil burner was out of oil for a week. I need to bleed the
my oil burner was out of oil for a week. I need to bleed the fuel line. When I got home yesterday my son had pushed the reser twice so I only got 1 try to bleed it and did not get oil out of the line.… read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
My beckett oil burner is out, started today I replaced the
started today I replaced the nozzle and filter for the heck of it all looked good … read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
When i turn my air conditioner on my oil burner runs also on
when i turn my air conditioner on my oil burner runs also on ruud furnace. i ohmed the thermostat wires to see if i had a short but they tested ok.… read more
Phil
Phil
Mechanical Engineer
Degree, Mech Engr Technology
6,730 satisfied customers
I have a Riello F40 Oil burner and this morning it starting
I have a Riello F40 Oil burner and this morning it starting making a loud noise. It seems to be burning OK. I took the red cover off and upon inspection I think it might be the fan bearing? I attached… read more
gmac2905
gmac2905
hvac tech
Vocational, Technical or Trade Scho
18 satisfied customers
My oil burner shakes the whole furnace when firing. All new.
My oil burner shakes the whole furnace when firing … read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
I got r7184b cad cell and beckett afg series oil burner,
i got r7184b cad cell and beckett afg series oil burner … read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
I have a oil burner that is not coming on. can jump
I have a oil burner that is not coming on . can jump thermostat on primary and it comes on , when it trys to come on with themostat or does come on u can hear the small transformer clicking, tapped it… read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
I'm changing the primary controller on my oil burner and I'm
I'm changing the primary controller on my oil burner and I'm a little confused about the wiring. The new controller only has 3 wires and the old controller had 6 wire. What's the correct sequence from… read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
Changed fuel nozel on becket oil burner burner working,
changed fuel nozel on becket oil burner burner working , leaking fuel from bottom of burner assembly … read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
Oil burner cracked.. we do not have the 5000 to fix it yet..
oil burner cracked.. we do not have the 5000 to fix it yet.. maybe a few more weeks.. its very cold tonight and we were wondering if you had any ideas to stop the pipes from freezing..or if you know a… read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
I have an industries laboratory oil burner, forced hot air.
I have an industries laboratory oil burner, forced hot air. It is 64 years old and surprisingly it still works fine. Years ago I wrote down the spark position and gap but can't seem to find it now. I … read more
Rick the plumber
Rick the plumber
Owner
9,857 satisfied customers
I'm attempting to replace a Honeywell R4184D1027 oil burner
I'm attempting to replace a Honeywell R4184D1027 oil burner primary with the newer model R8184G4009. I wired it up the same exact way as the 4184 and nothing happens when I turn the heat on. I did not… read more
Rick the plumber
Rick the plumber
Owner
9,857 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