Hvac not working..help!

[yourselferitdoer]

Hello all

Iam new on here,plumber by trade and will do my best to help in that department. Current situation is elderly parents hvac system not working,ive tried contacting acouple local hvac companies but with the current heat wave we are having they are not east to come by( I even know acouple personally!!) Anyway,I changed out a faulty thermostat for them last winter and Iam suspecting it could be that but dont have a clue when it comes to hvac.

System is an add on to forced hot air system in basement,have "Gibson" unit outside,system is approx. 15 or so years old. Heat still works fine, but when switching thermostat to cool,no blower,nothing..I have checked to make sure there was power getting to outside unit and there is,but not sure where or how to proceed. Any help is greatly appreciated !

Thank you in advance!

Mike

[HayZee518]

when the stat is set to cool, its output goes to a master relay. from that 24 volts is applied to the compressor contactor. internal wiring activates the condenser fan relay and also starts the evaporator fan relay. chek the fan circuit breaker and any push to reset fan overloads.

[HandymanTrainer]

open furnace door and tape the door switch closed, set t-stat to cool and auto, check for 24v on yellow t-stat wire at furnace, if 24v at yellow wire, make sure itis also connected to the red wire of a 2 wire pair that goes to outside unit. also check for 24v on green t-stat wire which is the fan circuit wire. if you are not getting 24v to either yel or grn you need to go back to the t-stat and check for broken wires ad that they are in the right locations, also in many t-stat with RH and RC terminals, there needs to b a jumperwire between RH and RC in order to activate the cooling section of the t-stat.

HandymanTrainer