Troubleshooting; Led Diagnostics; Table 4: Status Led Blink Codes; Table 5: Alarm Led Blink Codes - AAON MHGRV-X Field Technical Manual

TROUBLESHOOTING

LED Diagnostics

General
The MHGRV-X is equipped with LEDs that can be used to
verify operation and perform troubleshooting. There are LEDs
for communication, operation modes, and diagnostic codes. The
module has 14 LEDs—12 used for operation and status, and two
used for alarms.
See Figure 5, page 17 for the LED locations. The LEDs
associated with these inputs and outputs allow you to see what
is active without using a voltmeter. The LEDs and their uses are
as follows:
Operation LEDs
This green LED will light up to indicate that 24 VAC
POWER -
power has been applied to the controller.
This green LED will light up and blink the board
STATUS -
address at startup. It will then blink according to what mode the
controller is in. See Table 4, this page. Only the highest priority
failure code will be shown. You must correct the highest priority
alarm before other problems will be indicated.
No. of Blinks
1
2
3
4
5

Table 4: STATUS LED Blink Codes

Diagnostic LEDs
This red LED will light up to indicate an alarm. The
ALARM -
type of alarm will display on the LCD display. The ALARM LED
also blinks when the expansion valve is initializing at startup.
No. of Blinks
1 Supply Air Temperature Sensor Failure
2 Communications Time Out Error

Table 5: ALARM LED Blink Codes

Communication LED
This yellow LED will light up and blink when
COMM -
communications are detected.
16
STATUS LED
Off Mode
Reheat Mode
Flush Mode
Force Mode
SAT Sensor Failure Mode
ALARM LED
Relay LEDs
This green LED will light up to indicate that the relay for
FAN -
the "FAN" output is energized and its Normally Open Contact
is closed.
This green LED will light up to indicate that the relay
COMP -
for the "COMP" output is energized and its Normally Open
Contact is closed.
This green LED will light up to indicate that the relay
VALVE -
for the "VALVE" output is energized and its Normally Open
Contact is closed.
This green LED will light up to indicate that the relay for
AUX -
the "AUX" output is energized and its Normally Open Contact
is closed.
Binary Input LEDs
This green LED will light up when the
REHEAT ENABLE -
Reheat is enabled.
This green LED will light up when Heat
HEAT OVERRIDE -
Override is enabled.
This green LED will light up when Cool
COOL OVERRIDE -
Override is enabled.
Analog Output LEDs
CONDENSER VALVE DRIVE -
condenser valve is opening and reheat valve is closing.
This LED blinks any time the reheat
REHEAT VALVE DRIVE -
valve is opening and the condenser valve is closing.
LED Troubleshooting
When the MHGRV-X is powered up, the
"POWER" LED -
POWER LED should light up and stay on continuously. If it does
not light up, check to be sure that the power wiring is connected
to the board, the connections are tight, and the transformer is
powered. If after making all these checks, the POWER LED
does not light up, the board is probably defective.
As previously described, when the board is first
"STAT" LED -
powered up, the STAT LED will do the following:
• On for 10 seconds
• Blinks 30 times
• Blinks three times rapidly (after STEP LED is on for
45 seconds)
• Status code is repeatedly blinked every 10 seconds to
indicate controller status
MHGRV-X Field Technical Guide
This LED blinks any time the