2nd winter dealing with this issue... 1st time I replaced the thermostat and seems to work fine for a few weeks then problem came back. Now 2nd winter and problem came back after using heater for a few weeks this year.

Stat set to 72 but temp displayed will be 68. The only way I can get the heater to kick on is to switch the system off at the thermostat, wait for a few seconds for it to click, then switch it back to heater. After a second or two, I hear it click again then heater kicks on. This will last for a few cycles then the same thing happens again.

Sometimes it will run fine for days then it acts up again. What should I check before I schedule a service call?

You can remove the R and W wires at the furnace. Then using a jumper close the r and w terminals. This test eliminates the thermostat control and will tell you if the thermostat or the thermostat wiring is defective. If the furnace cycles a few time OK then the problem is not in your furnace itself. Note this is just for test purposes. Re attach r and w wires when done testing.

Thanks for the pointer. Before I electricute myself, thisis the W and R wire you are talking about?

http://home.roadrunner.com/~jpadilla/images/R-Wwire.jpg

NO. The wires are inside the furnace on the terminal strip. I have no idea what that transformer is for unless a humidfier is installed on your system.

I have lost no one to electric shock yet BUT there always is a first time.

Turn off power before removing the wires the after jumping the wires turn power back on. The switch on or next to your furnace can act as a on and off switch during the testing so you do not have to mess with the jumper and you will be safe from touching any wires whiule the power is on.

NOTE this is not the most perfect way to test but since you do not have a bunch of tools and meters it is the simplest one I know.

This are all the terminated wires I have, it's a TRANE unit. Thanks.

http://home.roadrunner.com/~jpadilla/images/IMG00116.jpg
http://home.roadrunner.com/~jpadilla/images/IMG00117.jpg
http://home.roadrunner.com/~jpadilla/images/IMG00118.jpg

Follow the small diameter wire with many wires inside that gose from the thermostat to the unit. You will see a terminal strip that says W R G Y or something like that. The R and W wire in that group is what I am talking about.

OK, I taped the furnace door switch so I can remove the door without shutting the system down. When problem came back... thermostate set at 72 and it was readying 70 and heater had not turned on. I removed the W and R wires and shorted the W and R terminals... the furcance kicked on. It then shut down when I removed the jumper. I replaced the W and R wires and the furance turned on again.

I do have a volt/ohm meter. Not sure what to assocaiate the problem to since I can't force the problem to happen, I just need to wait for it to quit working.

Basically your problem is intermittent. No meter is going to tell you anything as long as the system is working. You have to find the problem while the system is not working. I can imagine the aggravation but even a service person who would be at your home would find it difficult if not impossible to find the problem unless they started replacing parts. You already spent $$ on a thermostat you probably did not need.

Brand ?

Accurate model number?

I can search my records to see if that unit is prone to that type of problem.

Trane Model: TUJ080A948A1
80,000 BTU

The white module with all the wires terminals is a White Rogers 50A52-101. Only has 4 wires for the thermostate connect, no yellow.

There appears to be 2 sets of wires that are crimped together before it goes into the wire termal. One set runs to the attic above (maybe to thermostat), the other set goes under the fernace maybe to the outside unit.

By the way... Where can I send you a bottle of Jonhney Walker?

I can get no info on the board. See link.

White-Rodgers - Model Number Search (http://parts.white-rodgers.com/common/partsearch/search_common.asp?ITEM=50A52-101&CMD=DisplayInfo)

Now lets try something the old fashion way.

You said this is the second winter for this problem so lets look on the net for a possible fix.

Look here and read completely.

Trane XE80 blowing cold air - http://www.hvacmechanic.com/ Forums (http://www.hvacmechanic.com/forums/resservice/messages/15046.htm)

I would check the wiring while the furnace is running and also before you reset the next time there is a failure. During the failure mode I would move the wires around and see if the unit starts working. This is worth a shot.

The next item is standard fare since most furnaces today contain electronics and they do nopt like reversed polarity. They will sometimes work under reversed polarity but the furnaces have a bunch of symptoms similar to yours. Many times a fortune will be spent on replacement parts by the homeowner or a service tech only to find out when the real service tech gets there that polarity is reversed or the power has a poorly grounded system at the firnace/junction box, or at the house panel. Check for both. Here is a warning from White Rodgers on modules like yours.



The following steps must be performed first before any troubleshooting begins.
1) Disconnect electric power to system at main fuse or circuit breaker.
2) Visually inspect equipment for apparent damage. Check wiring for loose
connections.
3) Check for proper grounding and reversed polarity.
A. Check continuity for C terminal on module to electrical service ground and
connection at the furnace junction box. If ground connection is open, check
module ground connection and the electrical service ground connection.
Repair and retest.
B. Re-connect electric power to system.
C. Check for voltage between the line neutral terminal and furnace ground. If
voltage exists, the main power supply lines are improperly connected to the
furnace (REVERSED POLARITY). Again disconnect electric power to system;
then reverse incoming supply leads to furnace. Repeat step.
D. Recheck system for proper operation.
If neither apparent damage, loose connection nor reversed polarity is the problem,
proceed to troubleshooting chart or fault index chart that is suggested by the actual
Condition.

By the way ... Where can I send you a bottle of Jonhney Walker?


I really appreciate the offer as a gesture of good return on your part. Instead how about a small donation to your favorite charity to help those less fortunate than us during the Christmas holiday.

This way it will also keep the monkey off my back. LOL

Seems the problem is with the flame sensor... except I'm told good luck finding the part for my 1995 vintage furnace... the flame sensor is an optical one that is mounted right under the heating element (ignightor). I can't even find a damn part number on it to look for one online.

Post picture of flame sensor/radiant sensor. All parts are available for a 1995 furnace. Recheck your Model number and post again. This is a Trane unit?

I believe you have a radiant sensor. It takes my brain a bit to remember this stuff. I believe trane offered a conversion kit for this system. They had problems with the radiant sensor units. I will look in my old books.

Just found this on Ebay. I believe this is the complete change over kit with new circuit board. This gets rid of that old style sensor. You will have to install the entire kit with new circuit board etc. This is a cheap price.

TRANE KIT05216 RADIANT SENSE TO FLAME SENSE- NEW IN BOX - eBay (item 320318481269 end time Dec-15-08 14:54:59 PST) (http://cgi.ebay.com/TRANE-KIT05216-RADIANT-SENSE-TO-FLAME-SENSE--NEW-IN-BOX_W0QQitemZ320318481269QQcmdZViewItemQQimsxZ2008 1116?IMSfp=TL081116105009r14732)

Just found this on Ebay. I believe this is the complete change over kit with new circuit board. This gets rid of that old style sensor. You will have to install the entire kit with new circuit board etc. This is a cheap price.

TRANE KIT05216 RADIANT SENSE TO FLAME SENSE- NEW IN BOX - eBay (item 320318481269 end time Dec-15-08 14:54:59 PST) (http://cgi.ebay.com/TRANE-KIT05216-RADIANT-SENSE-TO-FLAME-SENSE--NEW-IN-BOX_W0QQitemZ320318481269QQcmdZViewItemQQimsxZ2008 1116?IMSfp=TL081116105009r14732)


Picture of what's in the box

http://home.roadrunner.com/~jpadilla/images/top_withIgnitor.JPG
http://home.roadrunner.com/~jpadilla/images/bottom_sensor.JPG

Yep you need the kit above I mentioned.

Thanks, seems KIT-9660 is the newest kit. I may not tackle this one myself... I mess with cars, computers, TV's, and such but this invovles more work than just a part swap.

It is a bunch of plug and play with instructions. The price on the kit was ereat. Dealers sell it for 350.00+ Then service call and labor. About 500-600 bucks. You can lead the horse to water BUT you cannot make them drink. LOL See you later.