Lincoln 2010 MKX Owner's Manual page 206

Driving
WARNING: To reduce the risk of electrical shock, do not use
your heater with ungrounded electrical systems or two-pronged
(cheater) adapters.
Prior to using the engine block heater, follow these recommendations for
proper and safe operation:
• For your safety, use an outdoor extension cord that is product
certified by Underwriter's Laboratory (UL) or Canadian Standards
Association (CSA). Use only an extension cord that can be used
outdoors, in cold temperatures, and is clearly marked Suitable for Use
with Outdoor Appliances. Never use an indoor extension cord
outdoors; it could result in an electric shock or fire hazard.
• Use a 16 gauge outdoor extension cord, minimum.
• Use as short an extension cord as possible.
• Do not use multiple extension cords. Instead, use one extension cord
which is long enough to reach from the engine block heater cord to
the outlet without stretching.
• Make certain that the extension cord is in excellent condition (not
patched or spliced). Store your extension cord indoors at
temperatures above 32°F (0°C). Outdoor conditions can deteriorate
extension cords over a period of time.
• To reduce the risk of electrical shock, do not use your heater with
ungrounded electrical systems or two pronged (cheater) adapters.
Also ensure that the block heater, especially the cord, is in good
condition before use.
• Make sure that when in operation, the extension cord plug /engine
block heater cord plug connection is free and clear of water in order
to prevent possible shock or fire.
• Be sure that areas where the vehicle is parked are clean and clear of
all combustibles such as petroleum products, dust, rags, paper and
similar items.
• Be sure that the engine block heater, heater cord and extension cord
are solidly connected. A poor connection can cause the cord to
become very hot and may result in an electrical shock or fire. Be sure
to check for heat anywhere in the electrical hookup once the system
has been operating for approximately a half hour.
• Finally, have the engine block heater system checked during your fall
tune-up to be sure it's in good working order.
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