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Jim Grant's Tech Tips
86
Chevy Astro, Power Door Lock Problems
Q:
I have an '86 Chevy Astro van. The problem is with the power door locks.
The passenger's side door will only lock and unlock via the passenger
door switch. None of the other door locks unlock when this switch is pressed.
The driver's side door switch does nothing. I have tried different switches,
on both doors. There are 12volts (DC) present at both switches, the door
lock control module, and relay. The relay does not engage when any of
the switches are pressed. Is the door lock control module bad or the relay????
A: I'd
suggest starting at the door lock relay. First answer this question, is
there an electrical signal (command) to operate present at the relay when
the switch is activated? (Not just voltage available, but a command to
operate.) The command to operate will be seen as change in voltage available
to the door lock relay. Realize that just because there is voltage (electrical
power) available doesn't mean the system is operational or a component
is functional. If a command is not detected at the relay, then move to
the door lock control module. Is the module receiving a command to operate
from the door switches? If so, is it sending the command to the relay?
If new lock switches didn't fix the problem, then you have to ask yourself
what's left? How about checking the wires that carry the signal between
the switches, control module and relay. A common area for failure is at
the wiring harness as it travels from the vehicle's body to the door by
the door hinges. Over time, the repeated opening and closing of the door
will work-harden the wires causing them to break.
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