Trane XE 70 Furnace / AC Air Handler - http://www.hvacmechanic.com/ Forums
Original message
| jcannon123
 |  "Trane XE 70 Furnace / AC Air Handler"
, posted Tue 4 Nov 20:40  
Problem...in the heating mode the blower motor will not come on in the auto mode.
Cold air conditioning mode works OK. However, in heating mode the pilot lights, the buner lights shortly thereafter, but the blower motor does not come on before the system times out and the burner shuts off. The blower motor can be turned on by moving the auto/manual switch to manual and heating functions OK.
What are the possiblities for preventing the blower motor from coming on when in the auto mode?
Thank you
Jim Cannon
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Replies:
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| Xenos
Webmaster 
| "Re(1):Trane XE 70 Furnace / AC Air Handler" , posted Wed 5 Nov 19:08
Could I get the model number so I can check if the fan switching is electronic or mechanical. Trane’s support site will not except XE70.
Xenos.
The best way to escape a problem is to solve it.
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| | jcannon123
| "Re(2):Trane XE 70 Furnace / AC Air Handler" , posted Wed 5 Nov 19:23
Per your request...
Model # TUS080A948A
Thanks,
Jim Cannon
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| | Xenos
Webmaster
| "Re(3):Trane XE 70 Furnace / AC Air Handler" , posted Wed 5 Nov 20:33
They must not support that number any more or at least I can find it. Since it appears quite old Here is a link that may be of use to you. Or at least get us started.
http://www.toad.net/~jsmeenen/blower.html
Xenos.
The best way to escape a problem is to solve it.
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| | jcannon123
| "Re(4):Trane XE 70 Furnace / AC Air Handler" , posted Fri 7 Nov 19:52
I went to the website you provided and read the material, but my furnace has one maybe two heat senstive solid state devices, not mentioned in the reading. One appears to be a simple temperature sensitive resistor (thermistor). The other probably the same, but in a metal casing.
I have the honeywell shutoff unit shown on the webpage, and it appears to be working to shut off the burner when it gets to hot. I assume it controls the blower on as well and if that is the case and the other devices I mentioned above have nothing to do with that, then it may be the problem.
Advice?
Thanks,
Jim Cannon
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| | Xenos
Webmaster
| "Re(5):Trane XE 70 Furnace / AC Air Handler" , posted Sat 8 Nov 06:38
Verify all the wiring is connected, Bad new is it may be the relay on the electronic board then as these do go. IF you have a meter you can verify if it’s closing or not.
Xenos.
The best way to escape a problem is to solve it.
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| | jcannon123
| "Re(6):Trane XE 70 Furnace / AC Air Handler" , posted Sat 8 Nov 14:20
I do not see any wires not connected.
There is no electronic board, however, there is an electromagnetic switch (coil relay), mounted on an aluminum plate by itself? I had assumed if that was bad the fan motor would not come on at all. The fan motor comes on in manual mode.
Also, when using the cooling side, the system functions properly in the auto mode.
Any idea about those two thermistors(?) I mentioned in my last note?
Thanks,
Jim Cannon
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| | Xenos
Webmaster
| "Re(7):Trane XE 70 Furnace / AC Air Handler" , posted Sat 8 Nov 14:30
If there is no electronic board it’s either the fan thermostat or this relay if this is a fan relay.
Xenos.
The best way to escape a problem is to solve it.
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| | jcannon123
| "Re(8):Trane XE 70 Furnace / AC Air Handler" , posted Wed 12 Nov 19:37
I inspected the thermostat and it appears to be good. I pulled the coil relay and could not determine if it was bad. The coil itself is OK, but I cannot be sure if the internal magnetic switch is working properly, because I am not sure of what all it supports and when and where voltage should show up on the contacts. Does it support both heating and cooling? There are seven contact points including the two for the coil itself.
I still don't know what the two thermisters do...not part of the Honeywell unit.
I would send you pictures of the internals of the unit, but I cannot paste them into this response. If that would help please provide an address to send them to.
Thanks,
Jim Cannon
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| | Xenos
Webmaster
| "Re(9):Trane XE 70 Furnace / AC Air Handler" , posted Wed 12 Nov 23:44
The 2 thermostats you are referring to will most likely be limits. You will have 2 fan control devices one for cooling one for heating. If you trace the wiring from the fan motor. It should lead you to the right component. If it a multi speed motor the heating speed is most commonly red or blue. Cooling is black
Xenos.
The best way to escape a problem is to solve it.
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| | jcannon123
| "Re(10):Trane XE 70 Furnace / AC Air Handler" , posted Sun 16 Nov 09:21
The Fan/Limit control (Honeywell) is the problem. I bypassed it and the system work OK, but for the continuous fan operation. There is a power switch on the outside of the furnace housing that can be used to turn the fan off and everything else for that matter.
I am now looking for a control replacement.
Any further suggestions?
Thanks for your help,
Jim Cannon
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| | Xenos
Webmaster
| "Re(2):Re(10):Trane XE 70 Furnace / AC Air Han" , posted Sun 16 Nov 09:55
Most Honeywell fan limit switches can be adjusted however if a new one is required most parts distributors stock Honeywell
Xenos.
The best way to escape a problem is to solve it.
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