Hello
I have a trane furnace that I started the other day, to check out and make sure it checked out for the winter, and it worked fine. I went to turn the furnace on again the next day and it never kicked on. So I started checking for error codes. I'm getting 3 flashes,which says it's a pressure switch.So I checked the pressure switch using ohms on my meter the switch works fine. I also waited for the furance to cycle and I jumpered the switch out with a paper clip. The furance does cycle but never ignites and when it starts to cylce doing this it gives me a 6 flash error code. Which says that it it's a reversed polarity or bad ground. So I next started from the 115 vac power source and checked it all to the board. It all checks out 115 vac all the way to the board and I checked it all to ground,good to go. So that next lead me to check the inducer fan, which in this whole process never turned on. First I checked to see if it was turning freely and it was I next checked if there was any obstruction in the flu or any where else. Everything is free and clear.I next check to see what voltage I'm getting at the inducer fan and its only about 3.5 volts. So I jumpered out the inducer fan to 115 vac,and the inducer fan runs fine. Just to be safe I also checked out the transform , 115 vac input and about 27.7 vac output. Next I pulled the control board to check for any burnt spots, blown capicatior or anything. The board has no dark spots or any noticeable damage. I can't think of anything else to test. I'm thinking it must be the control board, because I figure the inducer fan should be getting more voltage than that.But as I said before the board has no noticeable damage, so I'm really unsure where to go from here. Please HELP!!
Thanks Justin

This is for York but the reverse polarity problem has an effect on all electronic boards of just about all manufactures.

Just switch the two low voltage wires to reverse the polarity.

ALSO note.

The power to the unit must be exactly installed

Hot to 120 volt imput to board

Neutral to the neutral location

AND (very important)

The GROUND must be properly grounded to the unit and supply panel.

The grounding problems are causing major problems in almost all units.

York service

For Stand Alone Applications, Reverse Primary or Secondary transformer leads.
This does not mean there is any thing wrong with the boards, just that the transformer leads have been reversed or a phase shift in the transformer.


Full page here

http://yorkcentral.net/content/media...-ST-042-07.pdf

Thanks so much for help. I was thinking about reversing the low voltage leads, but didn't think that would be the problem because the unit has ran fine as it's wired for all of last winter . So naturally this has me a little confused why there would be a problem now. Also I do believe I have the unit ground well, I checked power from the power source and checked it all to ground. If I do reverse the low voltage leads and that's not the problem do I run any risk in damaging the board or anything else?
Thanks again for the help
Justin

If I do reverse the low voltage leads and that's not the problem do I run any risk in damaging the board or anything else?

There should be no problem if you reverse the leads. If that does not do the trick then you can switch them back.

I am making a guess here but is your unit a glow bar style called a HSI Hot Surface Ignition model? Does the glow bar light or glow at any time during the ignition process? Just curious.

I'm not really sure if it is HSI unit or not, but it's quite possible. Is there any place on the unit that will tell me if it's a HSI unit? When I jumper out the pressure switch and the unit kicks on nothing ever ignites or glows, but when the furnace was working normally I believe it did glow. Next I'm going to revese the leads and see what I get out of it, I'll let you know.
Thanks
Justin

You might want to post the exact model number just in case. Try reversing the leads first and see what happens.

Ok I just tried swapping the low voltage leads off the transformer and still nothing, I still to start with gave me the preesure switch error code. So I again restart the furnace waited for it to click over then jumpered the pressure switch and it still gives me the reverse polarity or bad ground error code, and that was with the low volgate lead swapped.
Here's the model # 2TXCCO43BC#HCAA

That model number does not come up on my computer records for anything Trane ever made. Please look on the inside unit for the model tag. It will have quite a bit of information on it and one of the numbers will be the correct model number. If possible take a picture of the tag and post it here. I need to see exactly what model you have so I can follow the wiring diagram since this problem seems to be a bit to complex for guess work.

Every year the major manufactures send the university a complete catalogue of there models and speciality devices so if that number was a good number for the entire inside unit I should have it.

You can change the low voltage wires back at this point since that did not seem to work.

Ok I wasn't to sure of the model number. That number was located at the top of the unit and did say model number, but I also noticed it said that it was a American Standard unit. On the outside cover it says it's a Trane though, not sure if that makes a difference. I also was looking at the control board and I do have that number handy if it makes a difference. It has a few number one is 50A55-571-04 and another one is CNT 2789. Not sure that that helps at all but first thing in the morning I will snap a few pictures of the unit. I'll take a pic of the model number and the wiring digram and anything else you can think of.
Thanks again
Justin

Your control trouble shooting guide

Pay special attention to sections 3,4 and 5

You may need some special tools for testing purposes.

You should have 120 volts for the ignitor to glow

You may also have to clean the flame sensor after all other work is done but that signal for the flame sensor can be tested also.

http://www.white-rodgers.com/wrdhom/...pg0259_264.pdf


This is a install manual for the control

http://www.white-rodgers.com/wrdhom/.../0037-5800.pdf

NOTE here is the complete list. You will see where some specific model numbers of Trane etc are not exactly covered in these manuals but these manuals will give you a start.

This is a list of the newer controls which probably do not apply to your unit but provided for reference only

White-Rodgers - Furnace ignition controls, ignitors


Here is a American Standard/Trane conversion package diagram just in
Case your was converted.

http://www.hvac.amickracing.com/Furnace%20Info/Igniters/SiC%20to%20SiNi%20Conversion%20Installers%20Guide. pdf

It looks like that's all the right stuff, here is a pic of my model number just in case.

Ok so I've been out of town for quite sometime then vaction, but I did go through all the troubleshooting service maunals and still can't figure it out. It wasn't much help when I went to test the pressure switch or the inducer fan,or I couldn't really find much to troubleshoot the control board. It seemed like everything I went through I was still back where I started. So wasn' sure if you might have any other suggestions? I was thinking about just replacing the control board even though I couldn't find any burnt spots. My other trouble is inside the panel it says replace with a CNT02183 control board or CNT02789, but I can't find any of those for sale. I did find a few CNT03797 control boards that said they replace a CNT02798. Not sure what to do.
Thanks
Justin

Many boards are substitutes or later improved models. Good luck with your search.

JustyluvsHvac: Did you ever solve the problem with your furnace? I'm having the same problem, and checked everything that you checked with the same results (except that by inducer fan only gets about 0.6 V). Any tips would be greatly appreciated!