2006 Lincoln Zephyr Low Beam Headlight Does Not Work

This 2006 Lincoln Zephyr came in with the complaint that the right low beam headlight does not work. The owner had already installed a new Xenon or HID bulb assembly. If you merely want to change the bulb there is an access panel in the inner wheel well as shown in the following picture. Since the customer had already advised me that they had installed a new bulb but that did not fix the problem, I did a quick test of the wiring and found battery voltage on the yellow/gray wire (terminal 6) with the low beams turned on. I also checked and found that the ground signal was present on the black/gray wire (terminal 1).

I had to go much deeper to get the light assembly out. This involves removing the entire front facia. I started by removing the retaining pins at both wheel wells.

I then removed the multitude of screws on the under side of the car that secures it to the body.

With everything loosened up, I found that there was one phillips headed screw at the outside edge of the facia assembly. I had to pull the inner fender panel back and use a screwdriver to remove each screw. One each side.  I forgot to take pictures but there are several phillips headed screws that have to be removed along the upper edge of the grill as well.

I though I had everything taken care of until I found that the facia would not come off. There was still something holding each side. I carefully inspected the situation and found locking clips at the body line.  I worked with it and finally released the clips.

The panel needs to be flexed enough to allow the inner locking hooks to come down far enough for them to release from the locking tabs.  In the next picture I am pointing to the hook that has to be forced down.

This is a picture of the locking tab that has to be forced up while the hook is being forced down.

The whole front facia off the car and on the floor.

The next picture shows the ballast or transformer module for the HID lighting system. I still needed to remove the light assembly to gain full access to the ballast/transformer.

There are four bolts and one push pin holding the light assembly in place. Two of the bolts are on the upper edge and there is a push pin at the top outer edge near the fender.

One bolt at the outer lower corner.

One at the inner lower corner.

The light assembly is out and I can now get the the ballast/transformer  module wiring with ease.

Four screws and the unit comes off.

I checked the wiring terminal locations on the vehicle harness connector.

I then matched the harness terminals to the housing terminals. Performed a continuity test from the housing terminals to the terminals at the ballast/transformer plug. I also performed a test from the ballast/transformer terminals to the terminals at the light bulb assembly. All continuity tests were good so the diagnosis is a faulty ballast/transformer module. I used probes with very fine wire tips to be able to touch the terminals without damaging anything.  Too large of a probe and or too much force and the terminals will be damaged. The wiring inside the light assembly cannot be repaired or replaced.  You must purchase a complete light assembly. DO NOT UNDER ANY CIRCUMSTANCES TEST FOR VOLTAGE AT THE BULB WIRING WITH THE VEHICLE HARNESS OR ANY POWER SOURCE CONNECTED TO THE LIGHT ASSEMBLY! YOU WILL/MAY BE PHYSICALLY HARMED OR KILLED!

A new ballast/transformer module and the low beam HID light is working again.  As a side note I did take the module from the driver’s side light assembly and installed it into the passenger side to confirm that the new bulb and the old bulb were both good. The customer wanted the old bulb installed. He purchased a new module from the local dealership. I reassembled the car and he put the new bulb up for future use.