Service Manual

18
C. Control Module Check
1. Control Module
Before replacing a CM that does not show a visible defect and that you suspect is bad,
conduct the following check procedure. This procedure will help you verify your diagnosis.
Always choose a neutral (W) to establish a good power supply and neutral connection to
CM: 115VAC at CM 2 (L) (BK)
2. Startup/Cool Down
At startup, CM displays a solid red LED for 5 sec. After 5 sec. CM turns red LED off and
begins ashing a green LED. This is normal operation. If a red LED ashes (fault code),
check CTh or DTh for continuity and good connection to CM.
1) Check all wiring connections.
2) Be sure the power supply is connected to the electrical outlet.
3) Conrm the CTh and DTh are properly connected (no red LED ashing). A Red LED
turns on for 5 sec. at startup. After 5 sec. the red LED turns off and a green LED starts
ashing. This is normal operation. If the red LED starts ashing, check CTh and DTh
continuity. Replace as needed.
4) Check that Comp, ConFM, and EvapFM energize (PH and MH on freezers). If not check
CTh status. If CTh ohm reading is in proper range,
Comp and ConFM and PH and MH (freezers); check for 115VAC at CM 1 (C) (BR)
to neutral white (W). If 115VAC is not present, replace CM. If 115VAC is present and
Comp energized and ConFM did not, check ConFM blades for binding and motor
winding continuity. If PH or MH (freezers) does not energize, check continuity, replace
as needed.
EvapFM; Check for 115VAC at CM 5 (F) (DBU) to neutral white (W). If 115VAC is not
present, replace CM. If115VAC is present, check EvapFM blades for binding and motor
winding continuity.
3. Defrost initiation
5) Manual Defrost Check: Turn the TD all the way to the right. Wait 1 to 3 sec. then back
to original setting. Defrost initiated. If Comp and ConFM continue, wait 1 to 2 min. and
repeat process of manual initiation. If Comp remains energized, replace CM.
6) Conrm Comp, ConFM, EvapFM (UC/WT refrigerator and freezer), PH and MH
(freezers) de-energize. If not, for Comp, ConFM and PH and MH (freezers), check for
115VAC at CM 1 (C) (BR) to neutral white (W) wire and for EvapFM (if applicable) CM
5 (F) (DBU) to neutral white wire (W). If 115VAC is present, replace CM. Note: EvapFM
continues on Prep Table models.
7) Heated Defrost: Conrm DH energizes. Check for 115VAC at CM 4 (H) (R) to neutral
white (W) wire. If 115VAC is not present, replace CM.