Garmin GPS 155 Repair Manual page 13

TROUBLESHOOTING CHART (cont.)
Display brightness not adjustable
Annunciators & Keycaps have no backlighting
Keycap backlighting not uniform
Annunciators do not function
No external annunciator output(s)
(message, arrival, approach)
Keycaps do not function properly
Dual concentric (rotary) knobs do
not function properly
Approach select switch not
functioning properly
OBS select switch ("course select"
or "hold") not functioning properly
GPS reception weak or GPS Status
Page shows low signal levels
No GPS reception
Unit displays velocity when not
moving 3
NiCad battery life is short
or NiCad battery inop
Unit loses memory in spite of new
memory battery
Unit does not detect low battery
Replace Pwr/Dimmer Switch (see Section 3.2.7)
Replace Main Board (see Section 3.2.4)
Replace Control/Display Unit (see Section 3.2.1)
Replace Main Board (see Section 3.2.4)
Replace Control/Display Unit (see Section 3.2.1)
Replace Control/ Display Unit (see Section 3.2.1)
Replace Main Board (see Section 3.2.4)
Check connections and verify operation in Test
Mode (see Section 4.3.2)
Replace Main Board (see Section 3.2.4)
Replace Control/Display Unit (see Section 3.2.1)
Replace Main Board (see Section 3.2.4)
Check wiring harness connection from rotary switch
to back of Control/Display Unit
Replace Rotary Switch Assembly (see Section 3.2.8)
Replace Control/Display Unit (see Section 3.2.1)
Check connections and verify operation in Test
Mode (see Section 4.3.2)
Replace external switch
Replace Main Board (see Section 3.2.4)
Check connections and verify operation in Test
Mode (see Section 4.3.2)
Replace external switch
Replace Altitude Decoder Board (see Section 3.2.2)
Replace Main Board (see Section 3.2.4)
Replace Antenna and/or antenna cable
Replace RF/IF Assembly (see Section 3.2.5)
Check Date/Time Page for correct UTC time 1
Check Position Page for close approximate starting
position (within 300 nautical miles) 2
Replace Antenna and/or antenna cable
Replace RF/IF Assembly (see Section 3.2.5)
Replace Main Board (see Section 3.2.4)
Replace RF/IF Assembly (see Section 3.2.5)
Replace External Battery Pack
Replace Main Board (see Section 3.2.4)
Replace Main Board (see Section 3.2.4)
Replace Main Board (see Section 3.2.4)
10