York Air Handler: AHP/MP
Re: Flashing Code 3
The control board in the air handler monitors the limit switch in the aux heaters.
Code 3 = Limit switch opened multiple times during a single call for electric heat.
► The control will energize the blower until power is removed from the control.
- The constant fan operation will signal the homeowner that a problem has occurred and a service call is required.
► The control will continue to cycle the heat outputs on and off as the limit re-closes and opens.
► The diagnostic light at the thermostat will NOT flash or provide any indication.
To Reset: Line or Low Voltage Power to the air handler control board must be cycled.
| Qty |
Possible Causes: |
| 1 |
Dirty Air Filter |
|
Heat Fan Speed too Low |
|
High Duct Static |
|
Failing X-13 Motor |
|
Bad Control Board |
|
Bad Limit(s) |
Checkout:
1. Check Cabinet Insulation
- Open the blower compartment and look for loose insulation that could block one or both sides of the blower.
- The most effective repair is to screw one or more metal straps the full length of the loose insulation.
2. Check for Water on Control Board
- Especially in counter-flow applications, the control board is extremely susceptible to water damage from condensate overflow.
- If there is water in the base of the air handler, or if the control board has obvious signs of water damage ⇒ suspect a Bad Control Board
3. Check Limits & Board
- Turn off power to the air handler.
- It is best to turn off power at the breaker box, as this test may bring you into contact with the inlet power wiring.
- Disconnect the white molex plug from the air handler control board.
- On the plug (not the board) check resistance between the Red and Brown wires.
- No Resistance Red to Brown = Open Limit
- Resistance Red to Brown = Limit Closed ⇒ Re-attach molex plug and re-power air handler.
- Still Code 2, 3 or 4 = Bad Control Board
4. Check Blower Operation
- Activate a call for Fan by one of the following methods:
- At the thermostat, turn the "Fan" switch to "On".
- At the air handler control board, place a jumper wire between "R" and "G".
- PSC Motor (AHP/MP)
- Check for 230VAC between "WHT" and "?" at motor.
- 230VAC + No Blower = Bad Motor or Capacitor
- No 230VAC = Bad Control Board
5. Check Air Filter
- With the old filter in, run the unit in "Em Heat" and check the temperature rise.
- Replace the air filter (if dirty) and recheck the temperature rise.
- Little or No Change = Filter (may need to be replaced but) Not the Cause
- Big Change = Clogged Air Filter