LCM woes, part III...

Removal of LCM underdash (right top). 1. Remove screws. 2. Depress locking tab.

Location of LCM (right bottom). 1. Remove screws, release locking tab, LCM inside.

To make sure you LCM is at fault here are some useful diagnostic tips: If your flash-to-pass function still works, but your headlights and high beams in the "on" mode do not work, then it's your LCM. The LCM just takes commands and process them. In the case of the high beams, there are two separate ways to switch them on and the flash-to-pass is independent of the "on" switch. If your high beams don't work in any method, then it may be the column switch. You can also verify the working order of your headlights by disconnecting the terminal at the bulb and sending 12 volts from the battery via a jumper wire to either of the light circuits (don't send 12 volts to the ground indicated by a black wire).

Not up to fixing your own LCM? Just want a new one? Well here is the scoop: You have several options.
1) Get one from Ford. Your dealer has them. The price ranges depending on how good of a negotiator you are. They retail for $511.07, but your dealer has discretion and may sell you one at the cost price, as low as $389.00. Online Ford parts sites, such as http://www.teamfordparts.com/ could be an even better deal if they list your part number. The LCM part numbers are 12 digits long and start with the year of your car, for example 5W7T-13C788-AB. This LCM would be for a 2005 Crown Vic. They are on a white tag on the bottom of the LCM.

2) Get one from a salvage yard. These are much cheaper (~$100), but they may already be on their last legs. Some salvage yards may sell rebuilt modules.

3) Go shopping on eBay. Two types are available on eBay. The first are just like the salvage yards, LCM's of questionable serviceability (think of all those taxis out there), and similar prices. The second type are people who use your LCM as a core and sell rebuilt modules. Here is the email of one such type: digitalguy_1@charter.net This source specializes in rebuilding automotive "black boxes". They come with a lifetime guarantee. The cost is about $100.

You should know that your are not alone and that faulty LCMs are very common issue with 2002 and newer Panther cars. It's not so much a matter of if, but when the LCM will fail.

Next: How to save your LCM and prevent early failure.

LCM woes, part II...

Replacing the faulty factory relays with a new standard 5-pole external relay is the next step in fixing the headlight failure for your Ford/Mercury LCM.

The LCM is located under the driver-side foot well above the gas pedal. Disconnect the three wiring harnesses, two screws, and push the tang to slide it out of its bracket. The box can be opened by pressing the tangs down folding the top on its hinges.

Locate the faulty relay on the inside of the LCM board as shown. You might notice a yellow discoloration or it may look overheated--that's because it was. All the headlight amperage flows through that tiny relay. All five contacts must be carefully de-soldered from the back of the board. (Be very careful. The board is very thin, the integrated printed circuits are very thin, and the you need a steady hand.) New small gauge wire (22 gauge) can then be re-soldered to the board and extended outside the LCM box. Label each wire for the five contacts (30, 85, 86 87 and 87a as shown). The new relay can be attached outside the box and zipped tied in place. It will now handle the job of the former tiny under-build factory relay.

Alternately, you can solder in a new replacement mini-relay. My research shows they are very hard to find, horribly back ordered, and the shipping for these tiny $4 relay makes them prohibitively expensive, thus the standard relay fix. Here are the part numbers: NEC part # EQ1-11111S or the better replacement NEC part #MR301-12HSL. Try Omni-pro.com or Mouser.com.

Next: More LCM fix/replacement options.

LCM woes...

There is a black box, about the size of a hard drive, under the driver's side dash of all Ford Crown Victories and Mercury Grand Marquis made between 1998-2010. It is called the Lighting Control Module (LCM). This box controls all the lighting functions of the car, and does so predominately with solid-state circuitry except for a few relays.

This makes for a very compact and centralized control for the varied options and customizations that a police/taxi/fleet vehicle must endure. However, it was engineered with a flaw: The primary relays, one of which controls the headlights, are inadequate. Specifically the headlight relay is know to fail after about 4-5 years of use due to heat. It's a rather small, and poorly made relay which is unable to handle the amperage (up to 10 amps) for the low-beam headlights--especially in a fleet vehicle which may have the headlights on all the time.

What are the symptoms of a failed LCM? First, your headlights may turn off and intermittently. Next, they will soon fail altogether. When you attemp to turn your headlights on will no longer hear the small "click" indicitive of the little headlight relay doing it's job deep in the LCM. High-beam and other lighting controls will still funtion normally. As an aside: There are other hard to diagnose lighting problems that can be symtimatic of a faulty LCM. These include (but are not limited to): Failed dash lights; other lights turning off and on randomly; random buzzer noises; and complete lighting failure.

What can be done to fix a failed LCM? The LCM is easily removed and can be replaced with either a new one ($375-$510) from your Ford dealer, it can be replaced with a used one from a junkyard (but it may be faulty or soon sucome to the same problems as it's old), or you can rebuild it by replacing the faulty reley(s) with new ones (about $4 each).

Next: How to rebuild your faulty LCM...