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Lennox Pulse

To perform a pressure test of the Heat exchanger. In 1997 Lennox had a recall of all Pulse furnaces made from day one (1981 I believe) up till January 1st 1990. The recall was due to an increasing failure rate of the stainless steel welds on the secondary heat exchanger. The rcall included a free pressure test of the HX, and free replacment of the HX including labor if it failed the pressure test standards set by Lennox. The recall lasted about 2 years. Since then Lennmox has mandated that ALL Pulse furnaces, including those that had the Heat Exchangers replaced, be pressure tested and have the air flappers replaced every four years. I have seen Pulses made after 1990, as well as Pulses with replacement heat exchangers fail the pressure tests during the last couple of winters.

Lennox is no longer making the Pulse furnace or replacement heat exchanger kits. To honor their warranty, they will provide a single stage 90% equivalent furnace as a replacement, with the option to upgrade to a two stage or two stage with variable speed blower for an additional cost. The consumer is responsible for the labor to install the new furnace and any other materials needed to properly install the provided furnace.


  • JoeJoe Member Posts: 1
    Lennox Pulse


    Are there any common defects with Lennox Pulse furnaces in the 20-25 year old range? If a house I was purchasing has one of these furnaces, should I have it looked at by a heating contractor for cracked heat exchanger or anything else? Or would simply installing a CO detector be sufficient?
  • GaryGary Member Posts: 35
    check it out

    You should call an expierenced Lennox dealer to perform a heat exchanger leak check. These lifetime heat exchangers are no longer available, however they do have a complete furnace (not a pulse)change-out program.
  • EmpireEmpire Member Posts: 2,343
    Recall on 1996 models

    There was a recall on these models for cracked heat exchangers. Wether or not it is still in affect, I don't know. The pulse also uses 2 flapper membranes, one on the intake and 1 on the gas manifold. The intake tends to break apart every 3to5 years. When doing service I like to remove the flapper and clean it with my fingers whick actually conditions it with the minute oil fron your fingers. Keeps it pliable a-little longer. Read your serial # and notice a date code like 94/96/98 in the 3 or 4 digits in the begining, this will give u the manufactors date code when the furnace was produced.
  • thpthp Member Posts: 122

    needs to be inspected by a Lennox dealer. More than likely you will be offered the chance to up grade to a new 90% model to replace the Pulse. If you know a Local Lennox dealer they can be quite flexable on what they give you inplace of the furnace. It does not always have to be a furnace.
  • GeneGene Member Posts: 289
    consider new

    seriously, these units had several problems and recalls, it was a good concept that failed, which is why Lennox stopped selling them, couldn't get the bugs out.

    Your instinct is correct and asking the question is smart, replace it.

    also check

    on one I found this statement"- - IMPORTANT UPDATE - -

    Lennox appears to have discontinued their free inspection program with respects to this furnace problem. The above telephone number will give you no useful information. If you suspect that you have one of the furnaces affected, I would recommend that you contact your closest Lennox dealer for a complete inspection, as soon as possible. Whether or not Lennox wants to accept further responsibility here or not, doesn't preclude the fact that a problem can exist with some of these furnaces. On a regular basis, I am still finding furnaces that have never been inspected for this problem and are in need of repair. Don't let a $60 - $80 service call stand in the way of your safety!"

  • Gary ReecherGary Reecher Member Posts: 111

    The secondary isn't the only place they will leak. Look at the attached photo. Shows where this one cracked on the resonator.
  • Gary ReecherGary Reecher Member Posts: 111

    The secondary isn't the only place they will leak. Look at the attached photo. Shows where this one is cracked on the resonator. As evidnenced by the large soap bubbles forming. Get them leak tested.

    Image hosted by
  • Ken D.Ken D. Member Posts: 820

    They had a recall on these several years ago. It only covered older vintages and only after they were inspected by certified dealers.I think units built before '99 or 2000. Unknown if the program is still in force. If the heat exchangers were found defective, they gave the customer a new furnace that was not a Pulse. For any information, call 800-4 Lennox or check their website at flame temperatures were so high the stainless steel tailpipes would crack. They were a good unit and efficient, albiet unique.
  • Gary ReecherGary Reecher Member Posts: 111

    From Lennox Service and Application Notes H-93-15 released December 14, 1993 and re-released on March 30, 2005

    In order to maintain the efficiency and reliability of the Pulse furnace, the following service guidelines have been established and should be performed on each scheduled service inspection of a unit. As with any gas-fired appliance, incomplete combustion (CO) caused by improper maintenance along with leaks in the system could result in serious personal injury.

    • Inspect heating system yearly. Inspect intake and exhaust PVC pipe for condensate leaks or joint separation. Repair, as necessary.

    • Check supply and manifold gas pressure. Adjust pressure, as necessary.

    • Check furnace firing rate by clocking gas meter. (Refer to installation instructions.)

    • Test oxygen / carbon dioxide level of flue gas to determine if proper combustion is taking place.

    • Test carbon monoxide levels in flue gas. Level should never exceed 50 PPM.

    • Check temperature rise and make sure proper blower speed is selected to match nameplate rating.

    • Inspect heat exchanger assembly for any signs of corrosion.

    • Inspect secondary heat exchanger for dirt build-up and clean, as necessary.

    • Inspect air diaphragm flapper material for dirt or deterioration and replace, if necessary. Air flapper material must be replaced every four years regardless of appearance.

    • Perform a pressure test of the heat exchanger and combustion chamber every four years.

    • Inspect gas intake flapper material for dirt or deterioration. Replace entire gas intake assembly if flapper material is found to be worn.

    • Inspect purge blower for dirt build-up every year and clean, as necessary.

    • Inspect stainless steel flexible gas connector for corrosion.
    Remember -- Some soaps used for leak testing are corrosive to stainless steel. Failure to thoroughlyrinse gas connector after leak check can lead to corrosion.

    • Check supply air blower wheel and clean, as necessary.

    • Check fan and limit controls for proper operation and setting.

    • Check all wiring for loose connections. Check for correct voltage.

    • Inspect intake and exhaust pipe terminations to make sure they are free from obstruction.

    • Inspect condensate lines for free flow of condensate during operation.

    • Instruct homeowner to inspect filter monthly and clean or replace, as needed. Dirty filters cause inefficient operation. Running the unit with a dirty filter or without a filter could cause premature
    heat exchanger failure.

    • Verify and check operation of existing CO detector.
  • Ken D.Ken D. Member Posts: 820

    The pressure test of the heat exchanger is the key.
This discussion has been closed.


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