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I have a Trane XB1000 heat pump. On Monday night, my wife

Customer Question
informed me that the upstairs...
I have a Trane XB1000 heat pump. On Monday night, my wife informed me that the upstairs unit in my house was not functioning and the temperature up there was 90 degrees. The downstairs unit was working fine. The air handling fan in the house was working fine. I examined the upstairs outside unit and the fan was not turning. The grill over the motor was very hot so I turned the upstairs unit off at the breaker box and let it cool off. I checked the capacitor with a Fluke 87V multimeter and it check out fine-5 microfarads for the fan side and 58 microfarads on the compressor side.(specs are 5/55 microfarads). I checked the contactor and it was working fine. After letting it cool off completely, I turned the power back on and the unit started up but the fan motor was making a worn bearing noise and the compressor appeared to be working fine. I removed the top grill and the motor and ordered a new motor which my wife will pick up tomorrow- diagnosis worn motor bearings.
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: yes the upstairs unit thermostat was working fine and the filters are clean. We continued to use the downstairs unit which did keep that zone of the house cool. However, today my wife informed me that that unit quit as well. When I got home, I checked the main breaker for that unit-OK. Had 240 V to the power side of the contractor but the relay was not working. However, it did work if I pushed in on the manual switch with a screwdriver- the fan came on normally, sounded good and the compressor seemed to be working fine. I thought it could be the relay so I swapped the relay from the upstairs unit to the downstairs unit and tried it again. Nothing. I of course checked to make sure the thermostat was set at 70 deg(ambient over 90 deg), on cool etc. I then jumped a wire from the yellow thermostat to relay wire on the upstairs unit to the downstairs unit, same with the blue wire and turned on the thermostat upstairs. The relay worked and the compressor and fine both worked. Of course, the upstairs fan went on but not the downstairs air handling fan. So it appears that it is a problem with the low voltage thermostat circuit- wiring, thermostat or a fuse for the low voltage system for the downstairs unit. My question is- how do I find the low voltage fuse for that unit and how do I test the thermostat?
JA: Do you plan on doing the work yourself?
Customer: Yes. I am quite capable in electronics.
JA: Anything else we should know to help you best?
Customer: I need to know where the low voltage fuse for the thermostat circuit is located so I can check it.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the HVAC Technician about your situation and then connect you two.
Submitted: 1 year ago.Category: HVAC
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Answered in 4 minutes by:
7/14/2016
HVAC Technician: airheatman, HVAC Technician replied 1 year ago
airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8,523
Experience: Furnace, A/C and heat pump specialist.
Verified

Let e make sure I understand everything.

1.Lookslike your upstairs fan is bad and you have ordered a motor.So that will correct that problem

2.Downstars contactor does not pull in by downstairs thermostat but it will from upstairs tstat with wires swapped.

Is this correct?

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Customer reply replied 1 year ago
correct.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Great Lets start by eliminating the thermostat. Reconnect the wires to proper outdoor units.Go to downstairs thermostat.Remove front cover. Loosen screws where wires connect to terminals and touch the R wire to the Y wire and tell me if contactors pull in and unit comes on.

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Customer reply replied 1 year ago
It is a white rodgers thermostat and there are three wires going to the mercury switch- white, yellow and blue. On the AC unit yellow and blue go to the contractor. Should I jump yellow to white?
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

What is model on the Tstat? Do you have a picture showing the wires?

If you have a paper clip icon on your page you can attach using that link.Or

You can upload the pictures using the tiny pic site .

Here is a link to the site.

http://tinypic.com/

Click on Browse , select the file from your folder.then click UPLOAD NOW.

They will give you a quote to enter in the box to verify you are a human.Enter the quote and click UPLOAD NOW

You will see your picture on right side of screen.

Then copy the link URL for email & IM

Paste that link here on the site.

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Customer reply replied 1 year ago
it is type 1F56W-444, LR27935 Class 2 (###) ###-####
Customer reply replied 1 year ago
it is similar as far as the top goes- fan auto on and system cool off heat but that is where the similarity ends. There is some additional numbers on the sub base- 9737 E78
here is a picture:http://tinypic.com/r/v74o5v/9
Customer reply replied 1 year ago
I don't know if I did that right- my 17 yr old son helped me with that. Are you able to visualize the picture?
Customer reply replied 1 year ago
I have removed them
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

what color wires are connect to what terminals

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Customer reply replied 1 year ago
A small red wire comes thru back and goes to terminal RH. A thicker red wire jumps from terminal RH to RC. A small green wire comes thru the back and goes to terminal G. A small white wire comes thru the back and goes to terminal W. Two small yellow wires come thru the back to terminal Y.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Excellent. Use a jumper or loosen screws and touch the red wire (Rh/RC)to the yellow wire (Y)and see if outside unit comes on.

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Customer reply replied 1 year ago
I jumped the Red to yellow wires and nothing happened at the unit. However, it starts right up if I manually push in the relay.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

OK next jump R to G Red to green and tell me if indoor blower comes on

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Customer reply replied 1 year ago
No the indoor blower did not come on
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

OK go ahead and put thermostat back together.We have an electrical issue .Thermostat not getting 24v signal from furnace.Go to indoor unit and give me model on indoor furnace

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Customer reply replied 1 year ago
Trane Model number TUE080A948K1 Serial Number M39531S1G
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

OKI want you to open bottom blower panel and see if there if a small 3 or 5 amp fuse on furnace control board.If so remove it and see if it is blown.

http://i.imgur.com/pKP74Wg.png

http://i.imgur.com/kYe4Epz.png

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Customer reply replied 1 year ago
Here is what I see inside the blower compartment. Should I remove the cover?http://tinypic.com/r/5vug5t/9
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Is this light on, off or flashing?

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Customer reply replied 1 year ago
OFF
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Ok if you will look at the chart on board that means we have no power to board.Push door button in and tell me if light comes on

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Customer reply replied 1 year ago
it flashes red when I press the door switch in
Customer reply replied 1 year ago
I put the cover back on the blower to depress the switch and i moved the float switch up and down but the AC unit did not start.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

See if indoor fan will come on with float switch lifted

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Customer reply replied 1 year ago
I was standing right next to the blower and did not hear any fan come on
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

OK but thermostat is still calling for ac Yes?

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Customer reply replied 1 year ago
good point. I had accidentally turned it off when I re-assembled it. Will try again.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Standing by

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Customer reply replied 1 year ago
No- does not come on with float switch in up or down position. The panel is flashing slowly with the door depressing the switch.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

OK somewhere we are losing the 24 volts from furnace to thermostat.May be a bad wire nut connection or something.Does that float switch wire into the red wire?If so might try bypassing it

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Customer reply replied 1 year ago
the float switch interrupts the small red wire. I bypassed the switch but it did not come on. The wire nut connections appeared sound.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Do you have a meter for checking voltage?WE are losing the 24 volts somewhere that tells thermostat to signal unit to come on

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Customer reply replied 1 year ago
I mean neither the blower or the outside unit came on.
Customer reply replied 1 year ago
I have a very good Fluke Multimeter.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

You disconnect wires to float and twisted red wires together right?

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Customer reply replied 1 year ago
regarding the way I jumped the switch- i pulled off the wire nuts and used an alligator clipped wire to connect the ends of the red wire. However, the red wires were still connected to the float switch.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

OK just making sure.I have had people twist float switch wires together.Lets check 24v out of furnace at R and C

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Customer reply replied 1 year ago
I have 27 Volts between R and C(checked on alternating current setting)
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

OK now do this.Turn thermostat to call for AC or FAN and come back to furnace board and check between G and C for the 27 volts

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Customer reply replied 1 year ago
With the thermostat calling for AC, door switch depressed, I only have 2.4 mv between G and C on alternating current setting.
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Go back to thermostat.Put the alligator jumper from R to G and check again

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Customer reply replied 1 year ago
I removed the sub-base on thermostat and jumped from G to RH. Still 2.4 mV between G and C
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

WE have a break in that red wire somewhere between furnace and thermostat

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Customer reply replied 1 year ago
Going back several screens, I never did see that fuse that you told me to check.
So If I understand you correctly, If I jumped a wire between R at furnace and RH or RC on thermostat, the system would work. Is that correct?
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Yours does not have the fuse. We have verified we have 27v leaving the furnace.

Red goes to RH/RC at thermostat

Thermostat is basically just like a light switch

On call for fan R and G circuit close and send the 24v back to furnace

On call for AC RH/RC, Y and G all close and send circuit to furnace blower and outdoor contactor.

Jumping R to G at thermostat is bypassing thermostat and should close the circuit back to G

Somewhere between where the red leaves R at furnace we are losing it or in other words have a break in the wire before it gets to RH/RC at thermostat

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HVAC Technician: airheatman, HVAC Technician replied 1 year ago

If you have a long piece of wire. Connect it to R at furnace and RC/RH .

Another thing you can try is put the alligator jumper directly from R to G on board and see if indoor fan come son

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Customer reply replied 1 year ago
Jump R to G at the blower box?
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Yes and see if blower comes on

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Customer reply replied 1 year ago
I jumped R to G at the board and the indoor fan came on
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

That proves as I said, there is a break in that red wire before it gets to thermostat

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Customer reply replied 1 year ago
I am going to run a long wire between R at the furnace and RC at the thermostat. Will that start the system?
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

It should.I will stand by

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Customer reply replied 1 year ago
OK
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Standing by

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Customer reply replied 1 year ago
Ran out of wire. How do I get back with you maybe tomorrow night when I have some additional wire?
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Just sign in and go to MY Questions

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Customer reply replied 1 year ago
Thanks will do
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

Sounds good

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Customer reply replied 1 year ago
Customer
Thanks for your very able help the other night. I am sheepish to tell you that I did not realize that the air handler and blower for the downstairs unit was in the crawl space and we were troubleshooting the downstairs low voltage control system using the upstairs furnace/blower which of course is not connected to the downstairs control system! At any rate, the problem turned out to be a faulty furnace service panel door switch on the crawl space furnace/blower unit which was jammed in the off position even with the door closed. The upstairs is now working fine since I replaced the motor and the downstairs is working fine since my HVAC friend bypassed the switch until I can get the replacement switch. Thank you so much for your help. I definitely learned a lot about the system with your help.
Bill
HVAC Technician: airheatman, HVAC Technician replied 1 year ago

If you have further questions, please let me know.

Thanks for letting me work with you.If my answer has been polite, professional,and thorough, please click one of the ratings before you go. If you still need help let me know!.Expert is not paid for assisting you until you rate answer.Feel free to follow up for 30 days at no additional cost. Bonus always appreciated if you feel justified.

To rate answer, please select one of the stars on the page.

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