Bulletin No.:

Service Bulletin

Date:

01-08-42-001N
June, 2021

INFORMATION
Subject:

Exterior Lamp Condensation and Water Leak Information and Replacement Guidelines

Models:

2022 and Prior GM Passenger Cars and Trucks (including Medium Duty Trucks)
(Excluding LCF Medium Duty Trucks)

Attention: This bulletin also applies to any of the above models that may be Export from North
America vehicles.
This bulletin has been revised to update the Subject, add LCF MD exclusion to Models, add
the 2021-2022 Model Years, add water leak example graphics and update information. Please
discard Corporate Bulletin Number 01-08-42-001M.

The following information is being provided to better
define the causes of condensation in exterior lamps
and includes guidelines for determining the difference
between a lamp with a normal atmospheric condition
(condensation) and a lamp with a water leak.
Some exterior lamps, such as cornering, turn signal,
backup, headlamps or tail lamps may exhibit very small
droplets of water, a fine mist or white fog
(condensation) on the inside of the lamp lens. This may
be more noticeable on lamps with “multi-lens” designs
and may be normal during certain weather conditions.
Condensation occurs when the air inside the lamp
assembly, through atmospheric changes, reaches the
“dew point.” When this takes place, the moisture in the
air within the lamp assembly condenses, creating a fine
mist or white fog on the inside surface of the lamp lens.
Most exterior lamps on General Motors vehicles use a
vented design and feature a replaceable bulb
assembly. They are designed to remove any
accumulated moisture vapor by expelling it through a
vent system. The vent system operates at all times,
however, it is most effective when the lamps are ON
and when the vehicle is in motion. Depending on the
size, shape and location of the lamp on the vehicle, and
the atmospheric conditions occurring, the amount of
time required to clear the lamp may vary from 2 to 6
hours. Customers with short commutes will experience
a longer time to clear the lamp.
Completely sealed headlamp assemblies (sealed
beams) are still used on a limited number of models
being manufactured today. These lamps require the
replacement of the complete lamp assembly if a bulb
filament burns out.

Copyright 2021 General Motors LLC. All Rights Reserved.

Condensation Examples

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Bulletin No.: 01-08-42-001N

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A Fine Mist or White Fog on the Inside Surface of
the Lamp Lens Occurring After a Period of High
Humidity
• May be located primarily in the lens corners (near
the vents) and SHOULD NOT cover more than half
the lens surface.
• The condition should clear of moisture when the
vehicle is parked in a dry environment, or when
the vehicle is driven with the lights ON.
• A comparison of the equivalent lamp on the
opposing side of the vehicle indicates a SIMILAR
performance.
If the above conditions are noted, the customer should
be advised that replacement of a lamp assembly may
not correct this condition.

Water Leak Examples
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Bulletin No.: 01-08-42-001N

June, 2021

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June, 2021

Bulletin No.: 01-08-42-001N

Numerous & Various Size Drops of Water Collecting
on the Inside Surface of the Lamp Lens After the
Vehicle Has Been Exposed to Rain or a Car
Washing Environment
Important: Moisture is most noticeable during the
Spring and Fall of year, due to high humidity and the
large fluctuation in temperature between day and night.
Note: Any of the conditions listed below would indicate
the need to service the lens or lamp assembly.
•

A condition that covers more than half the surface
of the lamp lens.
• An accumulation of water in the bottom of the
lamp assembly.
• A condition that WON'T clear when the vehicle is
parked in a dry environment, or when the vehicle
is driven with the lights ON.
• A comparison of the equivalent lamp on the
opposing side of the vehicle indicates a different
performance.
Note: A different performance of lamps on opposite
sides of a vehicle DOES NOT always indicate that one
lamp is bad, and the other is normal. For example, on a
cold day when the sun is hitting only one side of the
vehicle, the normal condition of one side showing clear
and the other showing fogging/moisture, could be
misinterpreted as a bad lamp. The customer may
comment that, or you may need to inquire if, the
moisture “comes and goes.” Moisture “coming and
going” is considered a normal condition.
If a lamp is found to be exhibiting a leak, review the
most recent version of Service Bulletin
02-08-42-001 for information regarding impact
damage and modification inspection.
Non-GM Headlamp, Tail Lamp and Fog Lamp
Assemblies
Many companies outside of General Motors are
manufacturing lamp assemblies that look very similar to
original equipment. They target high volume programs
like, but not limited to, Impala, Malibu, and Full Size
Truck. These lamps are most often presented by
customers as holding moisture or for inoperative bulbs
due to corroded electrical connections. It appears these
non OE lamps get installed on vehicles as part of a
collision repair. Most likely the customer has no idea
they are not original equipment, as the initial
appearance is generally good. Obviously, these parts
are not covered by warranty. Some of the common
company names seen on these lamps are Eagle Eyes
and Depo.

2650251

This fog lamp was returned for retaining moisture. As
you can see it is marked with the Depo brand (it is also
called out on the front lens).
The most reliable way to identify a non OE part is to
compare it to the replacement service part or a like
vehicle. Many do have the application called out on the
part with the letters GM being present. Notice that they
almost never underscore it, as that would be a
trademark violation. They often use substandard wiring,
sockets, vent patches and unsealed connectors.
Example of GM Trademark
Note: The graphic below is an example of a GM
Trademark that appears on some lamp assemblies.
Current assemblies contain the trademark on a label
affixed to the assembly.

3803767
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

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