SUBJECT:

DEW CONDENSATION IN HEADLIGHTS
AND TAILLIGHTS

No:

TSB-22-54-003

DATE:

APRIL 2022

MODEL:

All Models

CIRCULATE TO:

[ ] GENERAL MANAGER

[ X ] PARTS MANAGER

[ X ] TECHNICIAN

[ X ] SERVICE ADVISOR

[ X ] SERVICE MANAGER

[ ] WARRANTY PROCESSOR

[ X ] SALES MANAGER

PURPOSE
Some customers may report moisture or fogging inside headlights or taillights. This condition is
typically caused by dew condensation, most often on rainy days or after car washing. The
condensation normally dissipates within one hour after lights are turned on.
This TSB explains the difference between normal dew condensation, which is a natural
phenomenon, and water penetration caused by improper sealing or a defective/broken part.
NOTE: Each reported case should be evaluated thoroughly before replacing a headlight or
taillight. Only if normal condensation is ruled out, and the part is judged to be defective, should
a headlight or taillight be replaced. Replacement of a non-OEM exterior headlight or taillight
may result in claim inspection and debit.

It may be necessary to explain to the customer:
1. It may not be possible to prevent fogging of a headlight or taillight lens under certain
conditions.
2. Dew condensation is generated by differences of temperature, or after vehicle has been
exposed to water (such as rain or washing the car).
3. Humid weather may increase the condensation effect.
4. Condensation should dissipate within one hour after lights have been on.

AFFECTED VEHICLES
All U.S. Models

Copyright 2022, Mitsubishi Motors North America, Inc.
The information contained in this bulletin is subject to change. For the latest version of this document, go to the
Mitsubishi Dealer Link, MEDIC, or the Mitsubishi Service Information website (www.mitsubishitechinfo.com).

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PROCEDURE
If a customer expresses concern related to moisture inside a headlight or taillight, review all
the information in this TSB to determine the cause. After reading the entire TSB, determine
whether the light needs to be replaced.
• If the condensation dissipates after the light has been on for one hour, do NOT replace
the light assembly. Explain to the customer that this is normal dew condensation.
• If the condition is judged to be water penetration, and the moisture remains in the light
after one hour of the light being on, then the light assembly may need to be replaced.
Dew Condensation vs Water Penetration
The two main causes of a fogged headlight or taillight are dew condensation or water
penetration.
Dew condensation is a natural phenomenon and is not a part failure. It typically dissipates
within one hour after lights have been on.
In contrast, water penetration may be caused by a part defect such as improper sealing, where
large water drops remain inside and do not dissipate after lights have been on for at least an
hour. If water drops still remain inside the light after one hour, with lights being on, then
water penetration can be suspected.
Explanation of Dew Condensation (as a natural phenomenon)
Dew condensation occurs as a natural phenomenon: the inside of a windshield becomes
fogged when driving in rain, and house windows become fogged in winter.
Atmospheric air contains moisture even in fair weather. Higher temperature air can contain a
large amount of moisture, but when the temperature drops, the amount of contained
moisture decreases and the moisture that is left becomes dew condensation. This principle is
demonstrated in a fogged car windshield or windows on a house. The window is heated by the
warmer indoor air, which contains more moisture than the colder air outside. The window is
cooled by the colder outside air, which causes the warmer air on the inside of the window to
cool, and release moisture in the form of dew condensation.

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Dew Condensation/Fogging of Headlights and Taillights
Headlights and taillights become fogged as part of a normal dew condensation process.

While some of the suctioned moisture dissipates, some of it stays inside the unit. In
addition, resin materials of the light itself release moisture into the light unit as
temperature rises. This warmer residual moisture becomes dew condensation when it
contacts a cooler lens (for example, a lens that has been cooled by rain or washing the
vehicle).
Dew condensation most often occurs in the following conditions:
• Extreme temperature differences
• After washing the vehicle
• Driving in the rain
• Sunlight hitting the light in cold ambient temperatures (e.g., morning sun in winter)

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WARRANTY INFORMATION
This bulletin is supplied as technical information only and is not an authorization to repair.
If an affected vehicle is reported with the described condition, diagnose the condition,
repair if necessary.

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