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7-16
7-11: ELECTRIC 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.
Note: The sealed relays are
not replaceable. If a relay fails
the interface board must be
replaced.
Diagnostic LED Legend
CMP
CMPCMP
CMP indicates power from 12V transformer
indicates power from 12V transformerindicates power from 12V transformer
indicates power from 12V transformer
24
2424
24 indicates power from 24V transformer
indicates power from 24V transformerindicates power from 24V transformer
indicates power from 24V transformer
HI
HIHI
HI (RH) indicates output (closed) from right Latch
(RH) indicates output (closed) from right Latch(RH) indicates output (closed) from right Latch
(RH) indicates output (closed) from right Latch
relay
relayrelay
relay
HI
HIHI
HI (LH) indicat
(LH) indicat(LH) indicat
(LH) indicates output (closed) from left Latch relay
es output (closed) from left Latch relayes output (closed) from left Latch relay
es output (closed) from left Latch relay
HT
HTHT
HT (RH) indicates output from right Heat relay
(RH) indicates output from right Heat relay(RH) indicates output from right Heat relay
(RH) indicates output from right Heat relay
HT
HTHT
HT (LH) indicates output from left Heat relay
(LH) indicates output from left Heat relay(LH) indicates output from left Heat relay
(LH) indicates output from left Heat relay
AL
ALAL
AL (RH) indicates output (open) from right Latch relay
(RH) indicates output (open) from right Latch relay(RH) indicates output (open) from right Latch relay
(RH) indicates output (open) from right Latch relay
AL
ALAL
AL (LH) indicates output (open) from left Latch relay
(LH) indicates output (open) from left Latch relay(LH) indicates output (open) from left Latch relay
(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