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1.10 Interface Board Diagnostic Chart
The following diagram and charts provide ten quick system checks that can be performed using only
a multimeter.
Meter Setting Test Pin Pin Results
12 VAC Power 50 VAC Scale 3 of J2 1 of J2 12-16 VAC
24 VAC Power 50 VAC Scale 2 of J2 Chassis 24-30 VAC
*Probe Resistance R X 1000 OHMS 11 of J2 10 of J2 See Chart
High-Limit Continuity R X 1 OHMS 9 of J2 6 of J2 0 - OHMS
Latch Contactor Coil R X 1 OHMS 8 of J2 Chassis 3-10 OHMS
Heat Contactor Coil R X 1 OHMS 7 of J2 Chassis 11-15 OHMS
* Disconnect 15-Pin harness from the computer/controller before testing the probe circuit.
Diagnostic LED Legend
CMP indicates power from 12V transformer
24V indicates power from 24V transformer
HI (RH) indicates output (closed) from right latch relay
HI (LH) indicates output (closed) from left latch relay (if
present)
HT (RH) indicates output from right heat relay
HT (LH) indicates output from left heat relay (if present)
AL (RH) indicates output (open) from right latch relay
AL (LH) indicates output (open) from left latch relay (if
present)
PN 106-6666
NOTE - When testing on J1 and/or J2, use the
illustration above. Pin 1 is located on the
bottom right corner of both J1 and J2.
Disregard any silk-screened or painted
numbers on the board showing the location
of Pin1.