# Furnace flashes a fault code that doesn’t exist on Ruud chart



## Total Rebuild (Feb 2, 2018)

I’m having furnace issues. The short story is the system displays a "56" fault code which doesn't exist in the Ruud R92P (RFMA) documentation or anywhere that I've found on the internet. Can anyone help tell me what this code is? 

Not trying to DIY necessarily, as a female I just need to make sure the tech doesn’t give me the run around. 

Long story...

Issue: The furnace short cycles and we never reach the desired temp. During the middle of the night the house temp can drop as low as 57 degrees. There is nothing consistent about when the furnace blows warm or what feels like cold air. Pretty much does what it wants.

Troubleshooting details: Checked the furnace and it was flashing codes, “_”, “0”, “5”, “6”, “1”. I couldn’t tell the order so I flipped the breaker and watched the furnace cycle from the beginning.

1. Initially, code light reads “0” - no sound from the furnace.
2. Moved thermostat temp up to 80 degrees.
3. Code changed to H - motor kicks on and runs for a few secs, then you hear ignition and heating elements sound like they’re heating.
4. After about 60 secs a motor kicks on and system flashes - 5, then 6 several times.
5. Then code returns to "H" and motor kicks on again runs for a few secs and fan blows.
6. I check the vent with my hand, air feels warm. System runs for about 2 min, then fan stops.
7. Furnace ignites again and the fan comes right back on (this all happens in less than 60 secs).
8. System again flashes 5 then 6 for about 10 secs, then code returns to H. 
9. Blows for about 30 secs, then fan stops.

Steps 4-9 (skipping 6 - I didn't check each time as I was watching the codes display) continue for another cycle or two and then a new fault code is displayed... first a "10" then the "56" again...

1, 0, _, 5, 6, _

These codes flash several times, then when I checked the vent again air feels cold.

I scanned the QR code and pulled up page 86 in the installation guide. It gets me close to a diagnosis. Code "10" is a one hour soft lock out, but why the lock out? What is "56"????


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## DR P (Dec 16, 2017)

have you checked flue piping for blockages?
what are error code numbers listed above & below 56??
& what are the descriptions of these 2 listed codes???
wildcard - are there codes 5 & 6 separately listed?
consider trying a new pressure switch - if exhaust flue is clear
& assuming combustion intake air piping is also clear...

Peace


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## Total Rebuild (Feb 2, 2018)

DR P said:


> have you checked flue piping for blockages?
> what are error code numbers listed above & below 56??
> & what are the descriptions of these 2 listed codes???
> wildcard - are there codes 5 & 6 separately listed?
> ...


Flue piping blockages? No, I haven't checked the flue piping. 
Above/below 56? 
55 = pressure switch stuck closed when should be open 
57 = press switch stuck open when should be closed
Codes 5 & 6? No, I thought of that, too. Chart skips from "0" to "10".

I'll try and check for blockages. 

Might be important to mention that I started out simply trying to check/change the filter since we've been in the house 4-5 months and are just completing a renovation... I simply do not see that there is a filter anywhere on the furnace to change. I didn't think that the reno impacted the equation, because we didn't change any part of the system - nothing added, nothing removed, nothing rerouted. But with you asking about blockages it's likely that it's clogged somewhere.


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## DR P (Dec 16, 2017)

Do you have Whole house return grate(s) 
& have you checked there for filter?
What Did you renovate? 
& any dust or demolition debris created?

Peace


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## Total Rebuild (Feb 2, 2018)

DR P said:


> Do you have Whole house return grate(s)
> & have you checked there for filter?
> What Did you renovate?
> & any dust or demolition debris created?
> ...


There was a lot of dust and demo, but I will say the furnace wasn't running too great before this issue of short cycling on the extreme - high bills compared to neighbors and I felt like it was already short cycling nowhere this extreme, it was keeping us warm, so I was biding my time. One room stayed noticeably colder than others. (Btw, the tech isn't available until Wednesday, so I've bumped the therm down to 62, because it won't go any higher than 62 anyway). 

To answer the grate question there is a whole house return grate with no filter. All of the registers were replaced for cosmetic reasons and the garage was converted into a mother in law suite which required a 25 ft trench be dug and foundation repoured because there is no basement. All of the major sanding and painting was complete and the floor was repoured, and then I had the air ducts cleaned. There has been some touch up sanding and painting, but nothing major since they were cleaned.


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## Total Rebuild (Feb 2, 2018)

Total Rebuild said:


> There was a lot of dust and demo, but I will say the furnace wasn't running too great before this issue of short cycling on the extreme - high bills compared to neighbors and I felt like it was already short cycling nowhere this extreme, it was keeping us warm, so I was biding my time. One room stayed noticeably colder than others. (Btw, the tech isn't available until Wednesday, so I've bumped the therm down to 62, because it won't go any higher than 62 anyway).
> 
> To answer the grate question there is a whole house return grate with no filter. All of the registers were replaced for cosmetic reasons and the garage was converted into a mother in law suite which required a 25 ft trench be dug and foundation repoured because there is no basement. All of the major sanding and painting was complete and the floor was repoured, and then I had the air ducts cleaned. There has been some touch up sanding and painting, but nothing major since they were cleaned.


My edit didn't take... needed to add:

Checked out all of the potential clogging points that I could locate - nothing found, but condensation, very little soot in the pipe that leads outside. It doesn't seem to be at the right slope. Pretty sure that some of soot was mold. Placed a scrap of pipe under it so it will drain properly as a temporary fix. 

The condensation trap box and tubing: the 1/2" elbow has a kink in it. Seems it's too long, but I didn't find any clog there. Water still gets through, although if I knew more I might try and reconfig it to eliminate the pinch. Condensation in all of the tubing, but all fluid was clear - no debris or soot.

Pulled all of the trap plugs. Condensation was clear, nothing appeared in the trap to indicate possible blockage anywhere in the lines. 

The flue elbow joint? (black one on inside of furnace) there was rusty water, but there was also a little rusted screw in there. Seemed like too much rust to be caused by the tiny screw though. This joint was leaking. I could see where rusty water had leaked previously. Took it apart no blockage. 

Quite a bit of dust and debris outside the system around on the concrete floor. Shop vacuumed it up. System still coding.


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## DR P (Dec 16, 2017)

Hopefully your tech can de-bug your code &
address all the problems you have identified

Peace


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## oq1492 (May 31, 2018)

Hi Total Rebuild - I'm having practically the same problem, same codes, etc. The only difference seems to be that my cycle times seem to be a little longer than what you have reported. How did this get resolved? What was the Error Code 56? I'm not in the US, the techs that have looked at this so far don't speak English, and are as baffled as I am by the undocumented code 56.


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## oq1492 (May 31, 2018)

Mystery solved regarding error code 56. No doubt you also eventually found out that the error display was incorrectly oriented and was actually displaying error code 59 upside down. A quick flick of dipswitch SW1 to the OFF position corrected the display problem. However, I'm still interested in knowing how your techs corrected the underlying problems, and whether there is a happy ending to the situation.


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