How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask BillyHvac Your Own Question
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22633
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Type Your HVAC Question Here...
BillyHvac is online now
A new question is answered every 9 seconds

Should the red and yellow wires read 24-28 volts, like the

Customer Question

Should the red and yellow wires read 24-28 volts, like the red-green and the red-white. I am testing right at the air exchanger. I have a picture of the points of measurement.
Submitted: 2 years ago.
Category: HVAC
Expert:  BillyHvac replied 2 years ago.
what is the equipment
and what is the issue?
If you set for cool does the Y to ground have 24v?
use reply
Customer: replied 2 years ago.
I am not home at the moment to get you the air exchanger model number, but can provide this evening.The full background is:1) Bought a new Nest thermostat and installed on my main 5 ton zone.
2) The thermostat worked for a few days
3) The thermostat threw a warning that there is an issue with the yellow wire (cool)
4) In testing the yellow wire at the thermostat, the Nest would work when the multimeter showed the following.
- TEST A = Red lead from meter to red wire, black lead from meter to yellow wire. Reads 28 volts.
5) Currently, TEST A is showing 0 volts at the thermostat.
6) I traced back to the control board for the air exchanger and located the R, Y, G, W and Common posts where the thermostat wires attached.
7) Running TEST A on the actual control board posts is showing 0v.At this point, I feel like I may have a bad relay. Is there any additional information you need? Any ideas?I attached pictures of the control board where I am now performing TEST A and another of the relay model.
Customer: replied 2 years ago.
Do you see the two images? The first is the control board posts where I am doing TEST A from above (R and Y terminals). The second is one of the relays in the system.
Expert:  BillyHvac replied 2 years ago.
is the wire from outdoor condenser the other yellow one?
Customer: replied 2 years ago.
There were two different yellow thermostat wires on the Y terminal in the first picture. I know one goes up to the thermostat, but I am not sure if the other went outside.
Expert:  BillyHvac replied 2 years ago.
Can you follow it to a point you can tell which direction goes?