I've been working on a Carrier
58MVB060-F-12114 Furnace for the last couple days. The furnace would fire just in, nice straight blue flame with no hickups. After about 10-15mins the furnace would cut out and the board would show (LED) a "code 34 - Ignition Proof Fault." This problem will repeat and even fail on a code 14 eventually.
Gas pressure is acceptable to nameplate and componets all appear fine. Ground was fine, and even relocated. The unit is only 1 maybe 2 years old. Flame sensor was checked and even cleaned. I spoke with 3 Carrier service reps on the phone. First person told me to replace the board. The board was replaced and it failed again. Another told me to replace the electrode, so I replaced the flame sensor and still unit failed.
I had to pack up and do some research and ask some of my seniors. The next day I returned and tried a couple other things. I monitored the unit for 2 hours and it didn't fail once. Several hours later I got called back from the customer and the furnace was doing the same thing again.
The furnace is undersized for the buildng for 1, but shouldn't be a big deal, just take longer to heat the space. I live in BC, and lately it's been getting below 0'C and it almost appears that the unit fails when the ambient temp goes below freezing, otherwise I have no idea what the problem could be as it is intermitten. I suspect that it may not be the actual unit, but the venting that could be causing the problem.
Like I said, it runs fine for a number of minutes even hours and then will cut out all of a sudden and show an ignition fault. Can you give me any suggestions?