I install new thrmostat with a Trane 4 ton air con. My old Thermo had a blue wire i used it. now no work?

Question

I made a mistake and pluged blue into Rc and it should not of been connected. Now system will not come on. Is this a fuse or something

Thanks in advance

Answer 1

Is your A/C a heat pump? I think; (key word "think"), the blue wire is for the reversing valve on a heat pump. If so, you need to go into the "advanced set-up" and turn "on" the heat pump. The default setting is "off". the next step is the "polarity" either "B" or "O". I don't know what B/O means so you got a 50/50 chance of getting the polarity correct. (might mean blue or orange, according to which color you are using)
I had the opposite problem. My A/C is not a heat pump but the heat pump was turned "on" and the fan ran all the time but, no heat came out. Took me some "cold time" to find the problem and turn the heat pump "off".
Note: Some big commercial roof mounted "heat pumps" need to be in the "off" position. Check-out Richard A.'s link below (very informative!!!)
Good Luck to ya'.

Answer 2

If the furnace is a Trane unit, it should have a spade type fuse, and it now needs to be replaced. If its a older unit, it may not be fuse protected, and the stepdown transformer may need replacing. A word to the wise, the thermostat wire is installed by the hvac tech, and does not follow any rhyme or reason. So remove it from Rc and before you replace fuse or transformer. Check in your furnace or air handling unit to see what it is attached to. In newer furnaces and air handling units, it will attach at a terminal strip, this will be marked as is the thermostat, so put it to the same letter on thermostat as it is on the terminal strip.
If not, i would recommend calling a hvac tech, and having him determine what each wire should attach to, then label wires so as to not have problem again.

Answer 3

The blue wire was probably used as common and when connected to Rc caused a short and either blew a control fuse in the air handler or blew the transformer.

Answer 4

if you are lucky you blew a fuse. look around the transformer and circuit board, there should be a spade type fuse.

on trane, blue is common. (if its wired right to start with)

Possum, hvac guy

Answer 5

Depending on the age & style of your unit,you could have blown the fuse on the air handler circuit board,if so equipped.

Answer 6

Here is a link to a website that tells you what each wire does. It may help.

http://toad.net/~jsmeenen/wiring.html