Conventional system not cooling

[Mavonne_helper]

Hi, I have a 4 wire conventional system with a jumper on R and Rc (no common wire - but will install the nest power adapter when it arrives).  My issue is that my system doesn’t cool when the nest installed.

My nest wiring is Red wire =R, Green wire = G, Yellow wire =Y, and White wire = O/B 

The system comes on but does not cool when set to cool. Could the white wire be the issue?

thanks in advance

[HVAC · Accepted solution]

The white wire should go into W or W1 slot on the nest. Looks like you have a gas fired furnace. On your old thermostat there should be a switch of sort positioned in either in gas or electric heat. I’m guessing gas. So the white wire is used for heating and has nothing to do with the AC unless it’s miswired at the furnace control board. If you have a split system (furnace inside & AC outside) You need to check and see if your outside AC condenser is working when you have it in cool mode and temp is set below indoor temp you should hear the compressor working and the fan should be spinning and blowing warm air off the top of the unit. If you have a packaged unit (heat & cool all in one unit) might be on roof & need to make sure compressor & fan are working properly. What kind of system set up did you have on the nest? If you put the white wire on the nest slot O/B & set it up as a heat pump you might be powering heat & cool at the same time. Hope that helps. Good luck. 

[Mavonne_helper]

A swap of the white wire to W worked perfectly. Thanks so much!

[Markjosephp]

Hello everyone,

I wanted to ensure that everything was covered here.

On-point explanation, @HVAC. Thank you for the help here!

@Mavonne_helper, I'm glad to hear it was sorted out. I hope you've found the answer you're looking for. If you're still in need of assistance, feel free to let us know by creating a new thread.

Best regards,

Mark