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Revwags - Daytime Driving Lights Problem

455 views 1 reply 2 participants last post by  wmburns 
#1 ·
I have a 2002 GT Convertible and yesterday my Daytime Driving Lights started flashing. When I turn the headlights and tail lights on, they stop flashing, but when just the driving lights are on, they flash. Has anyone run into this problem, and do you know what the cause is?
 
#2 ·
The Day light running lights are an "option". That means that some cars have it and some do not. As such the circuit design is such that the output of the DRL module acts as a "bypass" to the regular electrical flow. If you think about it because of the bypass nature of the DRL module, the on/off action has to be:
  • In the DRL module itself
  • From a signal external to the DRL module
  • a wiring harness fault (unlikely in the case)


From the Ford Service manual
>>
Principles of Operation

Daytime Running Lamps (DRL)

The daytime running lamps (DRL) system operates the low beam headlamps at a reduced intensity. The DRL module (15A270) supplies pulse width modulated (PWM) voltage, approximately 75%-92% of battery voltage, to the low beam headlamps when the following conditions are met:

The parking brake control is released.
The high beam headlamps are disabled.
The ignition switch (11572) is in the RUN position.
The DRL module remains enabled when the low beam headlamps are turned on.
<<

To me the most obvious/reasonable external input that could "cause" the headlights to flash is the Parking brake activation switch not making good contact. Followed by a fault in the multi-function switch.

Of course there's always the possibility of a wiring fault.

Finally that leaves a fault (perhaps heat related) in the DRL module itself.

Do the head lights flash in a regular pattern? Is there anything else going at at the same time?
 
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