I have a Trane VX95 HVAC system that was installed in 2016 and manufactured 12/2015, model number in the heating portion shows TUN2B080A9V3VBA. I fired it up earlier in the week and got no heat out of it. Getting a code 2 on it. After it cycles I want to say 3 times through the whole startup sequence the inducer fan stops then the main blower motor starts running on one of the lower speeds. The 5A fuse on the control board is good. Here are the things I've done to troubleshoot it so far: I have pulled and cleaned the flame sensor (it didn't look bad at all). I made sure there was no water in the trap and all the drain lines were clean and clear and no problems with flow through them. I even bleached the trap just to make sure and blew out the lines and the trap. I made sure that I am getting vacuum on the vacuum lines (there isn't much at all though) and that the lines were completely clean and clear with no blockages. I checked for 24 volts at the transformer, and it was putting out about 27.5. I work with low voltage equipment access control, intrusion, and CCTV along with all the programming and such as a lead field service technician with Honeywell HBS, so this is pretty normal to see a reading of this to me. I am getting 51 ohms resistance on the igniter. I do not have a good view of it through the little window so I can't tell you if it glows or not since I have to run upstairs to turn the thermostat to heat so I can get a heat command to the unit, and from my understanding I will not be able to get back down in time to see it glow anyway. The inducer motor spins up as normal and some time in the cycle and I get voltage on the gas valve for a number of seconds, then things spin back down and it tries to start the cycle again. I hear relays kick in while this is all happening. Thermostat seems to be working as normal, and the air conditioning side works no problem. One thing I did note is that when I pulled the plug off of the gas valve, a White Rodgers 36J54-202 with Trane part number D674542P01 I get a bit over 5 million ohms of resistance between the high and common, and the low and common terminals. I get infinite resistance on between the high side and the low side terminal, which I would expect. When I troubleshoot wiring and circuits at work and I see resistances that high I generally say the wiring or whatever device is bad because it is pretty well infinite resistance. I simply do not know enough about troubleshooting this component to say anything on it, and I couldn't find the specs for resistance on it. I haven't troubleshot the pressure switch because I am not 100% sure what that would involve. It is a Honeywell C342634P62. I am sure that I could borrow a manometer if needed to troubleshoot it since it is a vacuum actuated switch it looks like. My question is where do I go from here, and what would you say is my problem based on what I have listed? Thanks.

Hello, We have an older York furnace which I don't have the complete part # right now but is is the P3UR series. It has had an intermittent issue since last season. About 8 months ago the control board would throw a pressure switch error. It happened like 6-8 times over a 7 month period and each time cycling power eliminated the issue for quite some time. at the end of the season it ran for a couple months with no issues. fast forward to starting to use it a couple weeks ago. This time furnace worked fine for days and then threw the following error 3 times in two days. now the error this season is "the fault indicates if the rollout jumper wire connection soldered to the board is broken the control needs to be replaced". Agian, if I cycle power the furnace will be fine for many cycles before the error comes in again. I purchased a new control board two days ago and put it in. the furnace went through many cycles throughout the day with the new board with no issues. yesterday it started throwing another error and woke up his morning and the blower and inducer were on but no warm air. With the new board according to manual is throwing the following error. "indicates the flame was sensed when there was no call for heat" ( thermostat was calling for it) . This keeps the blower and inducer on. Cycling power agian solves the issue for many cycles. This error says a leaking or slow closing gas valve could be at fault. So basically at wits end why all these errors and two different boards and different errors. Anyone with experience can you decipher this and advise if there is anything that could be common to all this that would stand out. My next move is to install a new flame sensor and pressure switch which I have new ones. Hate to throw parts at it but this one isn't easy. I am runling out the gas valve as I never had any issues with this error with the old board last season and have many good cycles with the furnace. Thx for any guidance.