# Can left over wiring (coming out of hole where old thermostat used to be) explain why 24 volts aren't reaching the compressor?



## HVAC1289 (Sep 28, 2021)

The wall opening where the original thermostat used to be has a conduit with 4 wires not connected to anything. I found this after the AC was not cooling and noticed the compressor was not getting 24 volts but the thermostat was putting out the 24 volts.
The old thermostat in this wall opening used to have a regular thermostat wire (5 wires) and the previous tech who moved the thermostat, seems to have removed it and left a 4-wire conduit. I would guess that the 4 wire in conduit were originally connected to the Y & C wires of the regular thermostat wire (2 wire out of 4) and when the tech removed this thermostat wire, left the 4 wire conduit as seen in middle picture of Diagram 1. 







Diagram 1.

The first picture shows what looks like the same conduit in middle picture. These 4 wires do not come out of wall to compressor. The 4 wire conduit from the left picture is connected correctly and receiving the 24 volts to activate AC but the 24 volts were not reaching the green and white cables coming from the wall that are supposed to be to activate the compresor. 
Now that I found the 4-wire compressor wire in the wall where the original thermostat was in left picture and it looks like the compressor wires in the left picture, I am wondering if having left the wires in middle picture out was causing the 24 volts to not reach the compressor.
I am including another diagram showing more. The house consists of a front part which has one HVAC unit which works and connects to the compressor through the conduit shown on the right picture above. 
The conduit that comes out to both compressors seems to carry the wires that come from both units connecting under the HVAC unit in back of property which is the one with the problem.
The compressor works fine if it is manually activated bypassing the thermostat. The problem is just that the 24 volts do not reach the compressor. 
I do not have access to the junction box as it looks like it is under the furnace in crawl space as diagram 3 shows and if it the open box shown in the last slide, the last tech sealed it!
Is this type of wiring something that used to be done a long time ago? 3 techs have said to just put new wiring directly to the compressor but I would like to know if anyone knows if this is just a matter of not leaving the new-found compressor wires out and disconnected as they were left.
Thanks in advance for your opinions, advice, knowledge!!


----------



## beenthere (May 30, 2009)

Sorry, we're a tradesmen only site.

Please use our sister site DIYCHATROOM.COM, thank you.

Thread closed.


----------

