Hot Topics: What's Wrong with My AC?

an AC unit's electrical connections

Here at we enjoy providing a place where home improvement novices and experts can come together to share ideas and advice. Inside our Forums, users can browse threads to see what exchanges are taking place on a topic of interest or start their own dialogue by posting something for the community to take part in. With over 250,000 members and counting, this resource is quite active so each week we highlight one of the conversations that may just help you with that next DIY project.

Original Post: What Is Wrong with My Air Conditioning System?

Pejman80st Member

Hi every one. I'm from Texas. My air conditioning start having problems a week ago. The ac guy came and said the the contactor and the capacitor need to be replaced, he also charged my system by 2lbs . After his repair, my fan wouldn't come on. I shut the system for 2 hrs and when he came to power the system, everything worked! He recommended to change out the fan if it happens again. The capacitor was reading 5, he said everything looks good. I bought a new fan and installed it myself. When I took the old one out, it was so hot, I couldn't even touch it for a second, it would burn instantly. So I got a new one installed. It worked but the problem was after the inside reached the designated temp, the fan outside wouldn't stop running. He came back and said the is no power going to control board, it needs a new board. I got a new control board and installed it. I still have the same issue with the fan.

Highlights from the Thread

PJmax Group Moderator

I'm guessing this is a heatpump system ?
When you installed the new fan motor did you use the required size capacitor ?

The fan was running. What was the compressor doing ?
A defective defrost timer board should not keep the fan running.

Houston204 Forum Topic Moderator

Connecting the wires to the capacitor incorrectly will do this.

Brown should be on Fan and blue should be on Herm.
2 yellow wires should be on C.

You will have 3 yellow wires on Com and 2 blue on Herm if someone added a start kit.

Pejman80st Member

The capacitor is 370 or 440 vac 50-60 hz. 5.0 mfd.

5x370/440 usa2029 by amrad.

The brown wire is on capacitor. The black one goes to the control board on the upper side and yellow is on com.

I have 3 yellow, one blue, one blue/pink, and one brown/yellow that goes to control board.

skaggsje Member

Looks like someone added a cap for the fan. Should be wired like this:

Here at we enjoy providing a place where home improvement novic

Houston204 Forum Topic Moderator

You need a bridge between the Com terminal on the big cap (which has the yellow wires) and one side of the fan motor cap if you have a 3 wire motor.

Kinda like the picture that I drew that Skaggsje has posted. 3 wire

A dual cap would have been better.

Read more at: //