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Wow just noticed that my phone was changing my spelling lol. Driers not dryers. System Diagnostics and Troubleshooting Procedures very good book on refrigeration. Not very expensive, got it off amazon some years back. It shows problems and the kind of symptoms that come with those problems.

On a Trane communicationg system there is not a run cap for the fan cause it's variable speed. The compressor will start first and then the fan starts. Communicating systems are very picky. Put the unit in charge assist mode if you are not positive what superheat it requires (normally ten-twelve). If the system shows complete charge, you know for a fact the system is charged right. I mentioned before about a bad high press cut out but have also replaced a couple of boards. Someone stated that a bad txv could be mistaken for a clogged drier filter. If the system was installed properly, pressure test, vacuumed, etc..the filter should not be clogged so soon, but to test this do a temp reading on both sides of the drier. You can also manually check operation of electronic txv by jumping out the test pins on the unit. As stated before....do yourself a huge favor and read the manuals carefully. With all this new technology that keeps changing...I won't call myself a pro yet...but have had a lot of experience diagnosing this equipment. I install them and service them ALOT....plus have spent many hrs on the phone with Trane reps who can't believe some of the problems I have found.

Yes dirty dryer will effect super heat and subcooling. Some people mistake bad txv and it was plugged liquid dryer. Best thing is to keep reading and enjoy fixing things. You seem to care so in my book your ahead of alot.

Originally Posted by ChaseAir

Always put your gauges on a system. You cannot begin to troubleshoot without superheat, subcool, temp diff across a coil, amp draws, static pressure and capacitor readings.

Not to be ignorant, however in school we were taught that the last thing a technician should do is put the gauges on. Rule out all other problems because you always lose a little refrigerant each time you put the gauges on and off. However in the situation the OP had I would have put the gauges on to see what the high pressure side was doing since it locked out on high pressure. However before I did that I would have checked the run capacitor on the condenser fan motor, checked to see if the fan turned easily, and I would have read the current on the condenser fan and checked it against the RLA to see if it was running harder than normal.

I am pretty new but I believe that this was probably caused by the fan not starting once and then the next time it started after you reset the board. I was on a service call once where the outdoor unit was not running. Turned out the compressor would start but the fan would not and it would cut out on high pressure. After checking the cap and windings I swapped the terminals and forced the fan backwards for a second and it loosened it up, after that it ran forward but took a bit to start. The current was about an amp higher than normal so we lowered the thermostat and let it run continuously (because we were afraid it wouldn't start again) until we could get a replacement motor a few hours later. So I guess my point is motors with worn bearings could start intermittently for several reasons.

I'm just thinking out load really.

I will definitely do that and thank you for the advice!

I have installed many communicating systems and over the past year I have had to replace several high pressure cut out sensors. It seemed to only happen on the 4 ton 20i's. In one situation, it was going off on high head pressure in the heat mode due to a bad cond. txv. At the time the unit was brand new and it caused me and Trane alot of headache. It's been almost a year now with no problems. Read the manuals on how to ohm out the cut outs. At first it can be very frustrating but once you learn it, you will be a much better tech on these new systems. Good luck!

Will Dirty Filter Drier's Change Superheat and Subcooling?

Sorry! I meant testo 550

What would i take a static pressure reading for? We just got a testo 510 at work i hope my boss let's me keep it in my truck. I used it once it is "VERY NICE" as we say in kazakhstan Borat!

Testo 510 best for reading static in my opinion.

a good multi meter has a capacitor tester. Magnehelic gauge is a pressure gauge for the ductwork. It helps evaluate airflow.
fieldpiece makes a good multi meter with an amp clamp temperature capacitance all in 1.
Uei makes a cheap digital manometer(another name for magnehelic gauge)

Could be. Time is money so you ain't got no time to be guessing what is wrong with the thing.

Question for ChaseAir:

How do you do cap readings and static pressure readings? I know how to do the others.

Do you think the fan was going on and off intermittently? I dont think it was the control board but wasn't sure. Its hard to determine the cause of a problem when the customer has had the system off for 24 hours and time is money you know!!

Thermal cutout (compressor overheat) could be caused by high superheat. High pressurelockout means the head pressure was too high more than once and the board locked it out from trying to start again. If your illustrious "teacher" is not going into these details but is rather changing random parts, you are in need of better tutelage.

Learn to take superheat, subcool, temp diff, amp draw, cap readings, static pressure readings and you will go far in your troubleshooting ability. Until you understand what these readings mean, it will be difficult to troubleshoot HVAC.

High superheat on a txv system could mean the txv is not opening enough.

The only reason I said low on refrigerant is because the outside coil was clean.

If it had high superheat than that means it is low on refrigerant? There wasn't any signs of that but then again the systems was off long enough to avoid those signs. I think the other service tech asked if there was water around the furnace and she said no.

Sorry, your problem was high pressure lockout, not thermal cutout. Blocked txv overcharge,etc,etc fan motor .....at least you ruled out the board. Get all your measurements.

I guess if Trane tests the control board I'll know for sure if that wasn't the problem. I'm a FNG in this field and I was with another service tech training me. I definitely agree on putting guages on at all times that will be kept on the top shelf when I get out on my own!!!!!!!

Trans has a service manual on them. High superheat can cause a reciprocating compressor to go into thermal cutoff occasionally.