07 Town Car LCM buzzing help

[Scooters Garage]

Looking for some help. The Light Control Module on 07 Town Car started buzzing intermittently about 6 weeks ago. It’s currently not causing any critical issues but I’m trying to get it taken care of before it does become critical. We’ve owned it for about 8 months. I’ve done the following troubleshooting and repair attempts so far without change. This is initiated by either unlocking remotely or by key.
LCM module number 7W1T-13C788-AA
1. I inspected and cleaned the A and B pillar, front driver and passenger fender body grounds.
2. Inspected splice by A and B pillar.
2. Pulled and replaced all relays in LCM myself.
3. New battery.
4. Disconnected drivers side head lamp connector while buzzing. No change.
5. Replaced the headlight multifunction switch.
6. If I pull either passenger compartment fuse F23 or F26 buzzing stops.
7. Buzzing stops after it warms up for a little while. Sometimes 30 seconds sometimes a couple minutes.
8. Lights and side markers flicker when buzzing as long as headlight switch is in off position. If I turn headlight switch into any other position the buzzing stops. Nothing stays on that after buzzing stops that I’m aware of.

According to the 08 factory manual F23 goes to something called “Logic Batt” F26 goes to “Batt2” in the LCM. Manual doesn’t explain what those are. I have the manual for the 08, not the 07. I’m hoping they are the same. Short story is I ordered the 08 manual thinking I was buying a 08. Surprise when title came in as 07. Anyway.

Any insight into what might be causing this would be helpful. I’m at the point where I’m going to buy back probes to start checking at the plugs. I’m also beginning to suspect that something is telling it to do that.

 

[Scooters Garage]

Ok. I’ve sat down and reviewed the electrical schematics and am wondering if the issue is with the Light Sensor. The part number appears to be 13A018. However for the 07 it looks to be an updated part number “unobtainium”. Local pull a part looks to have 2 08 Town Cars on lot. I’ll go see if I can get one or two tomorrow. If not I’m probably going to try to unpin the wire from LCM and see what happens.

Anyone ever had this. I’ll report back.

 

[driller]

I've looked into this as I recall hearing this being an issue in the past.

Apparently other Town Car owners have heard such buzzing which could be tracked to the LCM. The predominant theory is there is a relay in the LCM that is doing the buzzing. Relays have a propensity to do this if there is insufficient or unstable voltage to the relay. This could be the relay itself, a poor connection internal of the LCM or some cause of insufficient or unstable voltage outside the LCM.

I would advise to check and monitor the voltage input(s) to the LCM when it is buzzing and compare them to when it is not buzzing. A methodical process of elimination may reveal the source of the problem.

 

[N1ASS]

I found that one of the 6 transistors located on the one side of the LCM didn’t have the right wave form when I was using an oscilloscope. Removed the cage and It was dry from heat sink compound, replied new layer and all is good from 11 months ago.

______________________________

 

[Scooters Garage]

I found that one of the 6 transistors located on the one side of the LCM didn’t have the right wave form when I was using an oscilloscope. Removed the cage and It was dry from heat sink compound, replied new layer and all is good from 11 months ago.

Thanks for the input. I’ll keep that in mind.

 

[Scooters Garage]

Update. Last weekend I went to the local Pull A Part. They had two 08 Town Cars. I ended up pulling the LCM and Light sensor from both. The only issue with that is my 07 LCM was the 7W1T LCM, both the 08 LCMs were the 8W7T part numbers. A quick google search said they would work with the exception of possibly having to change the AS Built programming depending on which headlights you have Halogen (standard) HID (upgrade). I have the HID headlight option. I put the better looking 8W7T LCM and light sensor in. All looked good at first. I didn’t notice anything weird but it was daytime and garage tested. Good news is the buzzing went away and hasn’t returned. Bad news is I took it for a test drive at night a few days later/ago (at this point) the headlights would flicker and go out for a couple seconds at a time when slowing, stopping or starting. Apparently this is what it does when the LCM is programmed for the wrong headlight type. Different voltage or something. Soooo I ordered a OBDLINK EX and downloaded Forscan extended version. I spent a few days researching Google and YouTube university. The obd cable came in yesterday. So this morning I accessed the AS Built and confirmed that the 8W7T LCM was programmed for Halogen headlights. I then went on and learned how to extract the AS Built hexadecimal from the LCM, converted to binary, edited for HID, converted back to hexadecimal and installed back into LCM. I then tested. All seems good. On a side note. I noticed that before I changed the as built. If I hooked my bidirectional code reader up and force tested the HID lights I would get a “condition not met” message on my bidirectional reader. Now after changing the as built, I don’t get that message. It just says “on” now. So that might be a tattletale if your programmed wrong or other issues.
There are better posts on how to find, and modify the AS Built programming so don’t ask me. However if someone has a AS Built decoder spreadsheet for the Lincoln Town I would like to have it for future reference. There are multiple spreadsheets for other Ford products but I really couldn’t find any for the Panther platform.
I’m going to keep the original and if anything else goes wrong, I’ll probably look into fixing the original as N1ASS said. However I don’t have an oscilloscope. I just have a decent multimeter. I also have the other spare LCM from the second 08 Town Car.
Also while I was in there poking around I disabled the easy entry auto seat function that killed the original seat motor/gearbox.

 

[N1ASS]

Update. Last weekend I went to the local Pull A Part. They had two 08 Town Cars. I ended up pulling the LCM and Light sensor from both. The only issue with that is my 07 LCM was the 7W1T LCM, both the 08 LCMs were the 8W7T part numbers. A quick google search said they would work with the exception of possibly having to change the AS Built programming depending on which headlights you have Halogen (standard) HID (upgrade). I have the HID headlight option. I put the better looking 8W7T LCM and light sensor in. All looked good at first. I didn’t notice anything weird but it was daytime and garage tested. Good news is the buzzing went away and hasn’t returned. Bad news is I took it for a test drive at night a few days later/ago (at this point) the headlights would flicker and go out for a couple seconds at a time when slowing, stopping or starting. Apparently this is what it does when the LCM is programmed for the wrong headlight type. Different voltage or something. Soooo I ordered a OBDLINK EX and downloaded Forscan extended version. I spent a few days researching Google and YouTube university. The obd cable came in yesterday. So this morning I accessed the AS Built and confirmed that the 8W7T LCM was programmed for Halogen headlights. I then went on and learned how to extract the AS Built hexadecimal from the LCM, converted to binary, edited for HID, converted back to hexadecimal and installed back into LCM. I then tested. All seems good. On a side note. I noticed that before I changed the as built. If I hooked my bidirectional code reader up and force tested the HID lights I would get a “condition not met” message on my bidirectional reader. Now after changing the as built, I don’t get that message. It just says “on” now. So that might be a tattletale if your programmed wrong or other issues.
There are better posts on how to find, and modify the AS Built programming so don’t ask me. However if someone has a AS Built decoder spreadsheet for the Lincoln Town I would like to have it for future reference. There are multiple spreadsheets for other Ford products but I really couldn’t find any for the Panther platform.
I’m going to keep the original and if anything else goes wrong, I’ll probably look into fixing the original as N1ASS said. However I don’t have an oscilloscope. I just have a decent multimeter. I also have the other spare LCM from the second 08 Town Car.
Also while I was in there poking around I disabled the easy entry auto seat function that killed the original seat motor/gearbox.

I have programed several LCM's from Crown Vic's and Grand Marquis but I use my Bi Directional scanner XTool D9 Max and program all as Designer trim level this way it will work with any trim level Town Car.I have modified a 2010 Crown Vic LCM for my 06 Designer to work with all of my LED turn,brake,parking and Headlights so eliminated Hyper Flash.I do use Forscan from time to time but not as often since my scanner can program all modules and PCM,ECM etc.