Technical Section
67
Troubleshooting Chart
Symptom
Possible Cause
Corrective Action
Display is blank.
Fuse is blown.
No power to DIM.
DIM is defective.
Measure voltage at pins 33 and 34 on AOC.
The voltage should nominally be 24–30 VAC.
If correct voltage is measured, internal DIM fuse is probably blown.
Unplug 14-pin connector from DIM for 2 minutes. The internal fuse
will automatically reset. Plug unit back in and check display. If display
is still blank, check all wiring, etc. If no problems are found, replace
DIM.
If zero volts are measured, see
No power to DIM
.
Verify circuit breaker is on.
Verify transformer primary measures 110 VAC.
Verify transformer secondary measures 24–30 VAC.
Verify electric AOC panel is receiving 24–30 volts between pins 33
and 34.
If proper voltage is found between pins 1 and 2 of the DIM, all wiring
has been checked, fuses have been reset, and screen is still blank, the
DIM is probably defective. Replace DIM.
Control system is
not controlling.
Incorrect wiring.
Supply and exhaust
control wiring
reversed.
Verify correct wiring (see wiring diagram,
). DIM and
AOC must be wired exactly as shown.
Verify supply control wiring (pins 44 and 45) goes to supply damper
and exhaust control wiring (pins 46 and 47) goes to general exhaust
damper.