Need Opinion-Lennox Pulse problem

[Jeffrey R. Jonas]

I am looking for an educated opinion from an HVAC Guru, please...

I have already called for a service tech, and he will be here this afternoon. I am just trying to get an opinion so I can lessen the risk of getting taken to the bank. HVAC is my weakest area, so please excuse me if my terminology or assumptions are incorrect.

Unit:
Lennox Pulse
Model# G1403-80-19
Serial# 5891C15645
(March 1991)

Maintenance History:
(Owned home for 3 years)
Unit serviced when home purchased
General inspection performed monthly
Air filter replaced approx every 2 months
Last serviced 10/2008 (air flapper replaced at that time)

Problem:

On Thanksgiving afternoon, the unit shut-down, and would not respond to thermostat controls. Opened the access panel, and the green light on the control panel was lit. Inspected air filter, and was as new. Did not see any signs of burnt wiring, or other problems. I turned off the disconnect for about 15 seconds, and re-turned on. Unit started and operated normally. Decided to monitor situation, hoping it was just a fluke.

Early this morning, (2 am), the unit shut-down again. I performed what I did above, but this time no response. Turned on our portable space heaters and went back to bed.

This morning, (7am), I tried to reset the unit again. This time when I turned the power back on, I could hear what I assume was the draft inducer fan starting-up during the purge cycle. after about 10 seconds, I noticed the fan limit dial begin to move. After a total of approx 20 seconds, I heard another component (gas valve opening for ignition??) try to start-up and after 1 or 2 seconds, the entire unit shut-down. Control panel green light still lit.

Re-try... same as above. No response.

Called for service tech.

Re-try... unit started and is reponding. Currently maintaining temp.

Any help would be greatly appreciated.

Jeff

[Steven C. Waskewicz]

HSI (hot surface igniter) or Spark Ignition?
Sequence seems to be right, up until time for ignition...
does it glow? or does it spark?

the intermittent nature ( it is now running?) leads me to believe maybe
the flame sensor needs burnishing? check it out...

[Jeffrey R. Jonas]

Thanks Steven,

Closed chamber, no viewport, cannot confirm.

Sensor... makes sense (no pun intended)... not sensing flame/heat... shut-down before blower activates.

Yes, still operating, no problems.

Tech should be here in another hour.

Thanks for the info,
Jeff

[Michael Larson]

The tech should also do a Heat exchanger test.
The G14 was subject to a specail program from Lennox for exchanger failures. I had a client recently with the same unit.

http://www.inspectapedia.com/heat/lennox1.htm.

Locate the model number on the furnace data tag (either G14 or GSR14 followed by a series of numbers and letters) and the serial number on a tag below the name tag. The photo above [courtesy Arlene Puentes] shows a model number starting G14....
Homeowners who call the 800 number with the information will be told if their furnace is eligible for this inspection program.
The original Lennox furnace safety inspection program ran through July 1, 1999. If the warranted heat exchanger needed replacing, Lennox indicated that the company would provide a new heat exchanger at no cost to the owner. Labor costs for replacement parts are not part of the Pulse furnace warranty.
Owners of Lennox furnaces in this series who discover this fact after July 1, 1999 should still have the furnace heat exchanger inspected for safety, regardless of whether a new heat exchanger will be provided under warranty. A "rusty" heat exchanger, or one which has a rust hole or crack may be unsafe and risks leaks of dangerous, even potentially fatal carbon monoxide (CO) flue gas. See HEAT EXCHANGER LEAKS for more information about heat exchanger leaks and furnace safety and see Carbon Monoxide Gas Toxicity for information about carbon monoxide.

[Larry D. Kage]

Yup, good eye Michael.

I had one, too.

Good luck Jeff.

[Bryce W. Jeffrey]

My Lennox high tech piece of s---, was two years old when it quit. I was in Florida. On returning home the house was frozen. I am an old contractor and shut off the water, drained the lines and put anti freeze in the traps before I left. This furnace has gone through two electronic boards in the first three years. The boards were covered by warranty but I was charged with service calls each time. I now warn clients about the Lennox family and that "Dave" would be ashamed at the way they treat their customers.

Regards:

Bryce Jeffrey

[gkay]

Jeff there is not much you can do as a home owner with a lennox pulse. I'm sure you realize it is quite a unique furnace design. Other problems such as the gas flapper assemblie may require replacement every five years or like most home owners upon failure. The spark plug (and it is an actual spark plug) and flame sense plugs rarely fail. For smoother ignition and operation it is advisable to clean the gas velocity port which can be accessed through the spark plug opening, have your service tech do this as precise drill bits are reqired for each unit to clean off the accumulated rust, this should be done every few years as it does not take long with regular sheduled maintanence. Another common problem was the condensate trap at the end of the exhaust can plug. You can actually hear water gurgling in the drip leg beside the furnace if this is the problem. Make sure the condensate line is clear.

[Gary Reecher]

Don't forget the heat exchanger needs to be pressure tested every 4 years.

[Steven C. Waskewicz]

How did you fare with the tech on this Lennox?