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Hi
I have a York YP9C080C16MP12CB furnace. I was doing some work near the furnace and I noticed it was flashing yellow/amber 5 times. I checked the sheet attached to furnace door and for the 5 amber flashes it says: "High altitude OR vent, intake OR termination problem". Some sites I visited online say something like "vent and/or combustion air system is restricted" when discussing the 5 amber flashes.

There are two problems, for me, I hope someone can help me with. The first is what does these words mean? What is the issue causing the code? The second is how do I narrow all of this down to a fix? To further complicate things, the furnace seems to be working correctly. Thanks

UPDATE: Just went to the furnace to see what was happening and when I raised the thermostat to call for heat I was getting two flashing yellows only which says it is normal. Any ideas?

You can download the installation manual here.  See Page 40,

https://www.hvactechgroup.com/hvacforum/index.php?topic=749.0

QuoteFive Amber Flashes - Heating capacity is reduced due to restriction in the combustion air or vent system. Check for blocked vent/air pipe or clogged condensate drain. Above 4,000 feet altitude, this may also indicate automatic, normal derating for altitude. See page 7 for additional high altitude information.

It's an error that resets automatically so that's why everything is working now.

I would check to make sure there's nothing outside blocking the intake or vent or that the drain line from the furnace is not blocked with dirt.

Thanks Admin! Great resources and suggestions.

So I went out to check the vents as suggested and there were no blockages at the ends of the pipes. I didn't take the pipes apart to see if there was anything deeper down but I got the furnace to turn on and then went outside to check the vents. The exhaust was pushing out air (although it wasn't as strong as the air coming out of the hot water vent). On the other hand, the intake vent wasn't drawing anything at all. Is there supposed to be a noticeable draw of air going into the vent or is it just there? (If that makes any sense)

Is this due to a blockage further down? Is there a way to check/fix this without taking the vent apart? Or, is there an issue with a part in the furnace not drawing air in.

I haven't checked the condensate drain as of yet as there is water draining into the drain. Although, most of it looks like it might be coming from the humidifier. Thanks