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Headlights going out

2004 grand marquis’ headlights go out after being driven for a while, either gets too warm or hot, 2 mechanics have checked it out, one put in a new switch, not the problem, other doesn’t know what to do, can anyone help, hard to drive to work with no lights

If there is a headlight relay, this is a suspect. Another possibility might be the dimmer switch. My dad had this problem with a 1939 Chevrolet and nobody could seem to find the problem. He finally put fog lights on the car and would switch them on when the headlights failed. Finally, some mechanic did diagnose the problem and replaced the dimmer switch. I know that your car is 65 years newer than the 1939 Chevrolet, but cars still have headlights and dimmer switches.

I’d check the thermal breaker for the headlight circuit. Most likely the contacts that it mates to are loose and causing it to overheat.

The headlight relays are built into the LCM, and aren’t replaceable (except by replacing the LCM). It doesn’t have a “dimmer switch.” There is the multifunction switch, and two of it’s functions are flash-to-pass and high/low beam selection. It is unlikely to be the cause.

Well, I blew that one. I know that I had to replace the dimmer switch that was operated by the turning signal lever on my 1978 Oldsmobile. A rod ran from the turning signal lever to the dimmer switch. I didn’t realize that the dimmer switch is now built into the multi-function switch.

This problem is common on 03 and 04 models. Just in case anyone is interested, The LCM can be fixed by anyone that can solder on a circuit board. The relay can be replaced on the board or an external relay can be connected with wires. There are instructions at There is a forum set up called “Body of Knowledge”. Unfotunately, I think, you need to register to see this forum. It might be worth registering (free) since the LCMs cost over $400. If you can’t fix it yourself, but you can remove the part, an electronics repair shop might do it for a lot less than $400 if you take them the part and the article from the web site.

This sounds very much like what is going, just where would the thermal breaker be located? Do cars come with a schematic? I’ll let my daughter know-hopefully she can find someone to look into it, I would like to have my Toyota back so I can drive too. She has been using it for about a month since she decided the headlight business was too dangerous. Thanks!

What is an “LCM” and once again where is it located? Thanks, maudmerc

I would suspect its that LCM unit and would suggest going to that web site for the low down. I’ve had that with my Lincoln and with one of my Rivs. On the Lincoln it was the switch. On the Riv, it was somewhere in the automatic headlight circuit. When I pulled the fuse for the twilight sentinel, it went away so never bothered to fix it.

A bad component, or I suppose a connection, causes too much current to flow which overloads the circuit breaker. The breaker flips and lights go out. Breaker cools off and lights go on again. Its not the breaker but the component causing the overload.

The LCM is a Load Control Modular, and I have no idea where it may be located in your car.

Say what? The Ford factory service manual defines it as “Lighting Control Module.”

Thanks for all your hellp, I’ll give daughter info and let her take it from there…maudmerc