DIY Home Improvement Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 ·
Hello all: New to this forum. I have a problem with my Lennox G61MPV furnace; hope someone here has some ideas.


Furnace suddenly started to "flame off" 4 seconds after ignition. Everywhere I looked it said for this problem clean or replace the flame sensor. I bought a replacement and installed it — not easy since it was behind the ignition box. I removed an exhaust hose, installed the sensor, put everything back. Now the furnace is all but dead. No ignition, no automatic fan (fan works if turned on at thermostat). Circuit board alert is 5 + 2, which translates to "Internal error" — not real helpful.


I put the old sensor back in, but same thing: the furnace is dead. I checked all the connectors, they are fine. I shut the power on/off a few times. Left power off for a few hours. Didn't help. Did taking off the exhaust hose cause the problem? Is there a reset button? I am out of ideas.
 

·
Registered
Joined
·
14,063 Posts
Did you cut the power before changing the part?

Check for 24v ac between terminals R and C on the board with the door switch depressed. Check for proper incoming line voltage too.

If no 24v, check the low voltage fuse on the board.

Do not troubleshoot by changing parts.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #3 ·
Thanks for the reply.


Yes, I did cut the power before changing the part.


I did try cleaning the sensor first, but still got short cycling, so then I replaced it.


I will check those things you suggested. Didn't know there was a fuse on the circuit board.



Thanks agian.





Did you cut the power before changing the part?

Check for 24v ac between terminals R and C on the board with the door switch depressed. Check for proper incoming line voltage too.

If no 24v, check the low voltage fuse on the board.

Do not troubleshoot by changing parts.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #4 ·
There is proper line voltage, and there is 24v ac at terminals R and C.


BTW: I couldn't see any sort of fuse on the circuit board, but didn't worry about it since I do have 24 v ac.


What do I check next, please?



Did you cut the power before changing the part?

Check for 24v ac between terminals R and C on the board with the door switch depressed. Check for proper incoming line voltage too.

If no 24v, check the low voltage fuse on the board.

Do not troubleshoot by changing parts.
 

·
Registered
Joined
·
14,063 Posts
Board may have gotten damaged - what does the manufacturer say for "internal error?

Are you sure the new sensor and wire is electrically isolated and not leaking current to ground? (normally, board would give a flame sensed with no call for heat error, not internal error)

I did try cleaning the sensor first, but still got short cycling, so then I replaced it.
other things can cause the same problem.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #6 ·
Error code 5 + 2 states:
"Control failed self check, internal error (control will restart if error recovers)." ... not a big help (to me).



The wire appears to be electrically isolated: not touching any other metal parts. I will check it again. I could meter it to ground, but I'd be surprised.


Board may have gotten damaged - what does the manufacturer say for "internal error?

Are you sure the new sensor and wire is electrically isolated and not leaking current to ground? (normally, board would give a flame sensed with no call for heat error, not internal error)



other things can cause the same problem.
 

·
Registered
Joined
·
14,063 Posts
use a meter.

i suspect the board got damaged if everything external checks out - there's at least one lennox guy on this board, hopefully yuri will see this thread.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #8 ·
Okay. I metered it, and no shorts to ground.


Thanks for your thoughts on this. Circuit board sounds expensive.



use a meter.

i suspect the board got damaged if everything external checks out - there's at least one lennox guy on this board, hopefully yuri will see this thread.
 
1 - 8 of 8 Posts
Top