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7-12
7.9 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 1 of J2 3 of J2 12-16 VAC
24 VAC Power 50 VAC Scale 2 of J2 Chassis 24-30 VAC
*Probe Resistance (RH) R X 1000 OHMS 11 of J2 12 of J2 See Chart
*Probe Resistance (LH) R X 1000 OHMS 3 of J1 2 of J1 See Chart
Hi-Limit Continuity (RH) R X 1 OHMS 7 of J2 4 of J2 0 - OHMS
Hi-Limit Continuity (LH) R X 1 OHMS 4 of J1 7 of J1 0 - OHMS
Latch Contactor Coil (RH) R X 1 OHMS 8 of J2 Chassis 3-10 OHMS
Latch Contactor Coil (LH) R X 1 OHMS 5 of J1 Chassis 3-10 OHMS
Heat Contactor Coil (RH) R X 1 OHMS 9 of J2 Chassis 18-25 OHMS
Heat Contactor Coil (LH) R X 1 OHMS 6 of J1 Chassis 18-25 OHMS
* Disconnect 15-Pin harness from the computer/controller before testing the probe circuit.
Diagnostic LED Legend
CMP indicates power from 12V transformer
24 indicates power from 24V transformer
HI (RH) indicates output (closed) from right latch
relay
HI (LH) indicates output (closed) from left latch
relay
HT (RH) indicates output from right heat relay
HT (LH) indicates output from left heat relay
AL (RH) indicates output (open) from right latch
relay
AL (LH) indicates output (open) from left latch
relay
1
23
4
5
6
8
7
9
10
11
12
13
14
15
1
2
3
4
5
6
7
8
9
10
11
12
1
2
3
4
5
6
7
8
9
10
11
12
K1
K2
K3 K4
Left
Latch
Relay
Right
Latch
Relay
Left
Heat
Relay
Right
Heat
Relay
Test Points
J1 Left J2 Right
Diagostic LEDs