Chevrolet 1999 Express Van Owner's Manual page 161

NOTICE:
Don't lubricate the power antenna. Lubrication
could damage it.
NOTICE:
Before entering an automatic car wash, turn off
your radio to make the power antenna go down.
This will prevent the mast from possibly getting
damaged. If the antenna does not go down when
you turn the radio off, it may be damaged or
need to be cleaned. In either case, lower the
antenna by hand by carefully pressing the
antenna down.
If the mast portion of your antenna is damaged, you can
easily replace it. See your dealer for a replacement kit
and follow the instructions in the kit.
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