TM 5-4520-256-14
3-9. TROUBLESHOOTING - Continued
Table 3-2. Unit Troubleshooting - Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
Step 4.
Check for 88 (+/-2) Vac at B1 motor with OFF/VENT/HEAT switch (S1) in vent position.
NOTE
Voltage will be 88 (+/-2) Vac instantly, then increase to 120 (+/-10) Vac within 3 seconds.
If voltage is not present (indicating open in wiring) replace wiring (para3-32.1).
If voltage is correct, proceed to step 5.
Step 5.
Check for 120 (+/-10)Vac at output of K10 Timer Relay with OFF/VENT/HEAT switch (S1) in vent
position.
NOTE
K10 Timer Relay is a normally open relay and voltage initially will be zero, then after 3 seconds
goes 120 (+/-10) Vac.
If voltage is not present (indicating open in K10 Timer Relay) replace K10 Timer Relay (para 3-32.1).
If voltage is 120 (+/-10) Vac initially (indicating short in K10 Timer Relay), replace K10 Timer Relay (para
3-32.1).
If voltage is correct, proceed to step 6.
Step 6.
Check for 120 (+/-10) Vac at X1 of K9 Contactor with OFF/VENT/HEAT switch (S1) in vent position.
If voltage is not present after 3 seconds (indicating open in jumper wire) replace jumper wire (para 3
--32.1).
If voltage is correct, proceed to step 7.
Change 4 3-16.2
