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Ask Mat Your Own Question
Mat, Ford Senior Master Technician
Category: Ford
Satisfied Customers: 975
Experience:  11 yrs at FLM Dealer, Senior Master Tech 05-present, ASE Master tech, Auto trans & Diesel
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I have a 2003 ford expedition that the instrument lighting,

Customer Question

I have a 2003 ford expedition that the instrument lighting, tag light and tail lights are out. I have replaced the headlight switch and stack switch(wiper). I tested the factory trailer wiring and it only shows no tail light power. I can not find any blown fuses. What next? I need help.
JA: Have you checked the bulbs? Have you checked the connection?
Customer: Can the bulbs provide brake light and not tail light. If it is a bulb my wife is going to throw me out of the house. ( just kidding)
JA: Are you fixing your Expedition yourself? What have you tried so far?
Customer: I am fixing it myself. I have checked all fuses, replaced the headlight switch and stack switch. I tested the factory trailer harnesses with it only showing no taillight power.
JA: Anything else you want the mechanic to know before I connect you?
Customer: I think that is it
Submitted: 1 year ago.
Category: Ford
Expert:  Mat replied 1 year ago.

Hi I would like to help you out. The bulbs in your taillights have two filaments. One for brake light and one for tail/parking light. So if both left and right are out and also your plate lights are out then it most likely not 4 blown bulbs. Lets start with the rear lights first. Most likely you have an open circuit to the rear lights meaning the wire that supplies power to the rear lights is broken after the switch but before the lights. It is a brown wire. Ive included a picture of where to find connector c238.Located in the LF kickpanel. Large square connecter. Check for power on the brown wire with the lights on. if its ok there then we have to move to c405. c405 It located in the left rear drivers side of vehicle inside under the trim panel. If power is good at c238 you know from the switch to c238 is good, if no power at c238 you know your problem is between switch and c238. If power is good at c238 but no power at c405 then you know your wire is broken somewhere in between and you will have to trace it down. If power is good at c405 then you know your wire is broken after that connector but before all the lights. Its looks like this circuit runs on the inside of the vehicle. most likely traveling under the scuff plates you put your foot on to get in the vehicle. The plastic trim panel between the carpet and rocker panel. Water tends to collect under these scuff plates and eat away at wires so you may find your problem under there. If you need further assistance please feel free to reply and ask. But your problem is defiantly an electrical open circuit issue. Thanks

Customer: replied 1 year ago.
how do I check the brown wire for power. what type of tester and what do I put the leads to to test. I have many types of testers.
Customer: replied 1 year ago.
I also do not see a picture for the c238 connector location
Expert:  Mat replied 1 year ago.

A test light will work. just ground the lead on the test light and back probe the brown wire. A dvom will also work by placing the meter to the dc v scale and putting the black lead to ground and red lead to the brown wire looking for 12v on the meter. Ive included the picture of c238

Expert:  Mat replied 1 year ago.

Have you been able to locate the open circuit on expedition yet?