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  1. #1
    Join Date
    Nov 2011
    Posts
    7

    Lennox Pulse G21Q4-80-1

    Nursing my 18 year old Lennox Pulse 21 furnace

    Has been reliable for the past 10 years that we've owned this house. Recently been having a few no starts.

    Called my maintenance company = long story short, it was the ignition control board. Originally quoted a price, was then called back and that they were not available, but could be had for 3x the original quote and then they wouldn't cover the furnace any more. So I got one on the internet which I bought for 0.5x of the original quote and 1/6th of the second! This fixed the problem initially. Then the no start became intermittent. Have now changed the air flapper and spark plug. New flame sensor on the way. Plug and sensor threads looked rusty so used some dialectric grease. Removing the plugs is possible without using the special lennox tool. I used a plug socket with a short adapter that adapts the socket to a hex bolt and then a wrench on that bolt. Takes a little patience but quite doable. Waiting on a new flame sensor. Have not changed the gas flapper. The maintenance guy checked and adjusted the gas pressure and seemed to think the gas supply and value was OK.

    Have not been having any lock outs now but do notice that the furnace always seems to start on the third of the five ignition cycles before lockout. Is that normal? Almost seems like it takes 3 ignition cycle for the right air/gas mixture to be present at startup. Once running everything seems fine.

    Been interesting to see how these work. Seems pretty bulletproof if the common problems are addressed and are pretty easy to work on with a service manual (downloaded) even for an amateur. From what I could see with a mirror the HX etc looked in reasonable condition.

    So if the 3rd cycle start normal?
    Have quotes for a new system but on principle want to keep the old girl running or at least want to get thru to spring when prices may be lower and rebates may be available. Considering a Trane XV95 and 3 ton heat pump (XL15i). Seems my location (NoVA) is marginal for heat pumps though.
    Last edited by iamhives; 01-16-2012 at 02:43 AM. Reason: typos

  2. #2
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,705
    not starting until the 3rd attempt is not normal.

    has the venting been inspected and the heat exchanger pressure tested?

  3. #3
    Join Date
    Nov 2011
    Posts
    7
    Venting inspected=yes. Pressure testing = no

    Is the HX were leaking would there be other signs? Water leaking, CO detector going off?

  4. #4
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    great furnace
    has the drip leg been cleaned out flam senser almost never goes bad spark plug either
    is the cheap inducer working properly it needs to be freed up and oiled each year

  5. #5
    Join Date
    Nov 2011
    Posts
    7
    Will check the inducer fan - it runs but has never been oiled. If does make a bit of a noise. The fact that it always starts on the 3rd cycle might indicate the inducer is weak?

    I've checked the drop leg superficially and it does drain and condensate pump runs OK but not actually cleaned so so will try that also. The three cycle thing makes me think the inducer may be the best bet.

  6. #6
    Join Date
    Nov 2011
    Posts
    7
    Fixed !!! Touch wood. - thanks tinknocker service tech !!

    All I did was remove the inducer fan and oil the bearings. After initial removal the fan would only freewheel a handful of turns, after oiling perhaps 3 times longer. I also found about 8 carpenter bee carcasses in the inducer fan chamber behind the inducer fan - may indicate I need to clean out the inlet!!

    Turned the boiler on and off 5 times and started first time each time - so appears the inducer fan was not strong enough until the third cycle for the boiler to light. Inducer fan runs much smoother/quieter now.

    Happy camper..
    Saved me a 10k new system purchase ! (well,deferred really)

  7. #7
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    iducer works for 30 seconds to get the drat and air mixture right. Once the unit starts the induce shuts down and unit runs on its own. Then after call is finnished the induser starts to for 30 secs to purge all by produts from HX

    you need to find the bees nest and remove it
    find someone who can do a pressure test on the HX

    always like the g-14/ 21 unit

  8. #8
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary, or ask questions of the OP here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

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    Last edited by beenthere; 01-15-2013 at 05:07 AM. Reason: Non Pro * Member

  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,722
    JayPopple, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Your post has been deleted.
    Further infractions may result in loss of posting privileges.
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  10. #10
    Join Date
    Dec 2008
    Location
    Ontario Canada
    Posts
    534
    I don't really work in pulses, so please correct me if I'm wrong. But from what I understand, if a pulse is still living it should really have the HX PROPERLY checked as at this age, the chance of failure is quite high.

  11. #11
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,705
    should have the HX pressure tested every 5 years, i still find the failure rate to be low. i have quite a few in the 20-25 year range still going strong.

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