Overview
TroubleShooting
| Problem | Probable Cause |
|---|---|
| Won't Start |
|
Won't Start - Buzzing Sound at AC Unit |
|
| Furnace fan not turning on |
|
| Water running around the outside of the furnace |
|
| Fan on AC unit not turning |
|
| Not Cooling |
|
Checking Start Issues
Bypass the Thermostat
With the power on, you can bypass the thermostat by pushing the plunger in to connect the 240v.
Listen for buzzing, etc...
if it buzzes, check capacitor.
Check Incoming Voltage
Check for 240 VAC on contact points.
Capacitors
- Start Capacitor (black)
- Dual Run Capacitor(grey)
Checking the Capacitor
A problem capacitor may shows signs that it is bad by bulging out. Check to see if the capacitor appears misshapen.
The capacitor has a rating on it. Capacity is written as HERMS capacity + FAN capacity.
ex. 35+4uF
Measure the capacity from common to what you are measuring.
ex. Fan measurement should show 4uF and Herms should show 35uF.
Checking the Condenser Fan
Spin the fan with a screwdriver to see if it moves freely. If it doesn't you may need to replace the fan motor. You can also try oiling the fan.
Compressor
Ac Units
Mark's Unit
Sears Model# 875.47270
MD: 3207-1 11A
Notes:
Blue Box: Honeywell r8405b1009 (Fan Controller)
| Wall Wire | Thermostat Wire | Terminal | Usage |
|---|---|---|---|
| White | White | Common | |
| Black | Red | Power | |
| Red | Brown | Heat | |
| Orange | Yellow | Y | AC |
| Green | Green | G | Fan |
| Marking | Wire Color Code | Description |
|---|---|---|
| R | Red | Power, 24 Vac transformer |
| Rc | Red | Power from cooling, 24 Vac transformer |
| Rh | Red | Power from heat, 24 Vac transformer |
| C | Black/Blue | Common of 24 Vac transformer |
| W | White | Primary heat cell relay |
| E | Brown | Emergency heat relay |
| Y | Yellow | Primary cool call relay |
| Y2 | Yellow | Secondary cool call relay |
| G | Green | Fan relay |
| O | Orange | Change-over relay to cool relay |
| B | Blue | Change-over relay to heat relay |
| A | Heat and cool active to any relay | |
| L | Emergency heat active lamp | |
| X | System malfunction lamp | |
| P | Defrost control lamp |
References
| Reference | URL |
|---|---|
| How Air Conditioners Work | https://servicechampions.com/how-your-air-conditioner-works/ |
| AC Won't Start | https://www.youtube.com/watch?v=wzAA4dlp_70 |
| AC Capacitor Fail | https://www.youtube.com/watch?v=C82HvbvP08E |