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digital1 02-09-2011 04:40 PM

Help With Trane Furnace

I have a Trane Model #TUE100a936K3. It has 2 zones and is controlled by a Honeywell Controller.

I am experiencing an issue with my unit. Here's what happens:

If the unit is idol, and a both zones call for heat, the unit will go through it's normal start up with the small fan starting then it blows the fuse. The kicker is, if i take off the cover and do the same thing, it will not blow. Put the front covers back on and it blows within seconds. Even if the unit is cold. So it's not a heat buildup

I have:
- Replaced the main control unit. The one on the bottom of the unit with all the wires attached to it,
- Replaced the 24 volt Transformer the is behind the main control board.
- Checked the run of all the wires between the zone computer, thermostats and main control board. Everything is clean, no nixs, and all connections are tight and well contacting.
- Reseated everything that can connect making sure all had good connection.
- Checked to make sure nothing was getting pinched when putting cover on.

I have had a professional HVAC guy out, and he left scratching his head. HELP PLEASE!!!!

I'm good with a multimeter and following complex instruction. It's going to be -5 tonight and i would sleep better know it was running correctly. :furious:

Jackofall1 02-09-2011 04:47 PM

The small blower you are talking about, it that the combustion blower?

The cover you are talking about the upper cover? where the burner are or the lower cover where the main blower is?

Which fuse are you referring to, when you say the fuse blows?


digital1 02-09-2011 04:53 PM

Hi Jack,

Thank you for the quick response.
Sorry let me be more specific,

Yes combustion blower goes on for a couple seconds.

No upper and lower covers off. Yes, i know about the safety switch for the bottom cover. I have electrical tape around it so i can see whats happening.

The fuse i am refereing to is the one on the mail control board. Mine is a 3 amp fuse.

Jackofall1 02-09-2011 05:05 PM

I wasn't suggesting that you didn't know about the cover switch, have you tried this same thing with just the upper cover off and lower cover in place?


digital1 02-09-2011 05:14 PM

It's all good :-)

Yes same thing with any cover on it. My big question is how can the cover have anything to do with? It has no electronics associated with it.

Jackofall1 02-09-2011 05:17 PM

I don't know, looking at the sequence that a unit goes through covers or no covers sure seems strange.

I was thinking is there a condensate line from the pressure switch on the combustion blower being pinched when the cover is on?

My thought is, if this is the case could moisture in the tube be sucked back into the switch shorting out the contacts?

Try removing the hoses, installing the covers and powering on, the fan should run, the furnace naturally won't fire because the combustion air has not been proven.


digital1 02-09-2011 05:22 PM

I will try that in the next 30 minutes and email ya back with me results. Thanks again Jack!! :thumbsup:

Jackofall1 02-09-2011 05:25 PM


Originally Posted by digital1 (Post 587839)
I will try that in the next 30 minutes and email ya back with me results. Thanks again Jack!! :thumbsup:

Your very welcome, and I hope that we can get to the bottom of this very interesting problem.


digital1 02-09-2011 06:38 PM


No Luck. Put the cover on bottom only called for heat and pop, fuse blown.
Removed cover worked fine, and fired right up!


college A/C 02-10-2011 01:18 PM

blown fuse
Do the covers touch the gas manifold in any way when installed? and is the gas valve assembly grounded?

UFoPilot 02-10-2011 01:30 PM

Make sure you have the right "kind" of fuse, slow blow vs. fast blow. Also check the exhaust vents for blockage.

digital1 02-10-2011 02:21 PM

The fuse that is on the control board looks like any normal type 2 prong automotive fuse. I replaced it with the same color and AMP fuse.

digital1 02-10-2011 02:22 PM

No i made sure it is touching nothing. I also made sure no wires were being pinched or even touching

rditz 02-10-2011 02:41 PM does have any information on the model you mentioned. do you have the manual?? have you checked it for possible reasons why fuse would blow??


digital1 02-10-2011 03:40 PM

I've had 2 different HVAC guys out. And the left scratching their heads...... It a little more involved than opening the manual that came with it.

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