Lennox G60UH(X) series furnace: troubleshooting alternating fast flash


  #1  
Old 02-04-11, 07:11 PM
N
Member
Thread Starter
Join Date: Feb 2011
Location: usa
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
Lennox G60UH(X) series furnace: troubleshooting alternating fast flash

i had a tech from Reiner inspect my problem, that my furnace was not working properly (continually going into lock out mode). He deemed it to be a dirty flame sensor. Sensor was cleaned and flue was checked and verified clear. I was told the pressure switch could be faulty as well if problem persists. Well, system ran for one day then stopped. So, I replaced the pressure switch and no help. Currently the diagnostic codes are alternating green fast flash. On turn-on, the system energizes but the initial ignitor warm up period never begins. According to the manual, three possibilites;

1. improper main ground
2. broken ignitor or open ignitor circuit
3. line voltage below 75 volts

Am I heading in the right direction? If so, any guidance on how to troublshoot these would be very helpful. I followed the ground and all seem goof, but I'm not sure which one is the main ground. Is it the one connected to the burner shield?

Not sure how to know if the ignitor is broken without replacing. As for the circuit, followed the white wires and seem to be connected. Tomorrow I will get my multimeter out, but what is the easiest location to check the line voltage? Any help would be great as a new home owner I can't afford to have a tech show up again....their houlry rates are something i would expect of a lawyer!
 
  #2  
Old 02-04-11, 07:33 PM
G
Member
Join Date: Oct 2002
Location: Hamilton County, Ohio
Posts: 3,927
Upvotes: 0
Received 2 Upvotes on 2 Posts
The line voltage is probably fine. Check the HSI by unplugging it and do a continuity check with your multimeter. Zero or low ohms is a good circuit. Infinity means the circuit is open -eg. bad HSI.

If HSI is good, turn off the main power feed to the furnace and then connect your multimeter to the connector which normally feeds the HSI. Set the meter for 120 vots AC or higher. Then restore furnace power and set the thermostat for a heat call. The inducer motor should start and in about 1/2 minute the meter should swing from zero to 120 volts. If not, either the pressure switch is not pulling in or the control board has a problem.
 
  #3  
Old 02-04-11, 08:03 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post
Am I correct that the hot surface ignitor gets white hot, that the main burner gas switches on and that the main burners light, only to shut off after being lit 3-5 seconds or so?


The diagnostic code is indicating that either the main burners aren't lighting or the flame rectification signal is not being detected by the ignition module.

No harm in verifying that 1230 VAC is being applied to the HSI, although it's unlikely that's the problem.

You need to measure the microamps of DC current flowing along the wire from the flame sensor to the ignition module.

Start by measuring and reporting here the AC voltage being applied to the flame sensor when the main burners light.

1000 microamps = 1 milliamp. You need a good multimeter able to measure down to 1 microamp or less.

Put your multimeter in series with the flame sensor. Measure the DC microamps flowing when the main burners are lit. A good reading is usually about 5-6 microamps. A poor reading of 1 microamp or less will cause the burners to shut off and the diagnostic code you are getting to be displayed.


This is the kind of diagnostic procedure your repairman should have performed and no doubt did not. Cleaning the flame sensor usually solves this kind of problem, unless something else is the problem as in your case.

A pressure switch has nothing to do with this problem.


The bottom line is that you may have an ignition control that isn't detecting that the main burners are lit and is therefore shutting off the gas as you describe. That could be because no AC voltage is being applied to the flame sensor by the ignition control, because the DC flame rectification current isn;t being detected by the ignition control or because of some other defect in the system.
 
  #4  
Old 02-05-11, 10:22 AM
N
Member
Thread Starter
Join Date: Feb 2011
Location: usa
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
Lennoz G60UH(X) series furnace: troubleshooting cont...

Thanks for both your responses...here's what i found with the multimeter.

1.67k ohms at HSI - I believe low enough to consider good circuit, thus good HSI

0 to 115 volt swing coming to the HSI at turn-on, but then shuts off and drops to zero after 20 seconds or so.

I also tried to the microamp reading at the flame sensor and I got a zero microamps reading. Now I'm still not sure if i did this right. I pulled off the connector to flame sensor, attached multimeter connectors between flame sensor butt-end and metal tab on wire.

the weird thing is the following; currently right now when i turn the furnace on (with everything connected in standard manner) and have the thermostat call for heat, the combustion air inducer turns on for +/- 20seconds. then another operation begins which I beleive to believe the ignitor warm up period. However, no ignition occurs, it just turns off. the HSI never gets white and doesn't look hot. it used to ignite a couple days back before the tech cleaned the flame sensor, but it would then shutdown less then a minute later. (i;m not blaming the tech, because my system worked for one day before it totally kicked the bucket)

Anyway the reason I question my methods for testing the microamps is because when I disconnect the wire from the flame sensor and hook up my multimeter in series, the furnace acts differently. It still goes through the 20 seconds combustion air inducer routine and still fails to ignite, however instead of shutting down, the fan continues and it blows cold air through my ducts...

thanks for the help.
 
  #5  
Old 02-05-11, 12:28 PM
G
Member
Join Date: Oct 2002
Location: Hamilton County, Ohio
Posts: 3,927
Upvotes: 0
Received 2 Upvotes on 2 Posts
Since you are getting voltage from the control board to the HSI connector and it is going off after 20 seconds, the sequence up to that point sounds right. With the HSI hooked up, it should glow bright red/white hot for those 20 seconds.
I just tested a brand new HSI (spare) and my analog meter shows zero ohms. It sounds like your HSI has gone bad. They are very fragile and a slight bump, skin oil from touching them, or just age can cause failure.
 
  #6  
Old 05-10-11, 08:58 PM
B
Member
Join Date: May 2011
Location: canada
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
Did you end up solving your issue? What was the solution?
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: