GMC 2003 GMT560 T-Series Owner's Manual page 229

Relay Block B
Relay Block B Usage
1 Air Conditioning Condenser
2 Air Conditioning Compressor
3 Heater Fan
4 Ignition Accessory
5 Ignition 1
6 Ignition 2
7 Auxiliary
8 Horn
9 Ignition 3
10 Dome Lamp
Relay Block B Usage
11 Exhaust Brake
12 Power Take Off Control
Relay Block C
Relay Block C Usage
1 Parking Brake
2 Daytime Running Lamps On
3 Daytime Running Lamp Off
Parking Lamps/Daytime Running
4
Lamps
5 Neutral
6 Stop Lamp
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