LCM problems?

[ben735]

So I have searched quite a bit and can't find exactly what I am looking for.

Does the LCM control the dash lights and headlights with the same relay? Are there any other relays for the dash lights?

Symptoms are: Headlights (set on High or Low, Auto or demand) will go out together with the dash/cluster lights. I do not loose parking lamps, turns, or tails, just headlights and dash/cluster lights. It happened quite a few times while driving last night, but I have had trouble getting it to repeat in the driveway. From what I remember I believe that I am loosing the backlights to the HVAC as well.
This has the original, non upgraded LCM. I am planning on upgrading the LCM to external relay, but I am concerned that this will not fix my dash/cluster issues.
Thanks,
Ben

[Gryphonzus]

If you are not proficient in soldering I would recommend grtting in touch with Fastblackmerc about fixing it. I know when I do mine I replace all the relays and put the larger headlight relay externally. There are several relays inside the LCM. I am pretty sure Fastblack does the same thing.

[fastblackmerc]

I can repair your EATC & LCM.

Sounds like the relays in the LCM are on their way out. The only lights that are not controlled by the LCM are the brake lights.

I install a heavy duty - 40amp external relay for the headlights and replace the other three internal relays with 20amp units.

I can install LEDs for the button and fan wheel lights for the EATC and I also do the o-rings - included in the price.

I guarantee the parts and my work for the life of the vehicle.

PM me.

[ben735]

I have the parts and skills required to upgrade myself, although I might take you up on the offer. What do you charge to repair/modify the LCM?

Also, can you confirm what relay supplies power to the cluster backlight? Forgot to mention that the cluster still works, I'm just loosing the backlight.

THanks,
Ben

[whitey]

Here you go! Easy peezy! https://uploads.tapatalk-cdn.com/20180202/38fc35a2433745826e59c432984080 f4.jpg

[whitey]

For the headlights. From this you should/will be able to figure out where which wires go for the other relays according to the size of the holes in the pcb. 87a isnt used for the headlights and can be left unsoldered. https://uploads.tapatalk-cdn.com/20180202/7447995b4901e3323b00cc85750aeb 0c.jpg

[ben735]

Haven't had time to get everything back together and take her for a road test, but for anyone considering having fastblackmerc upgrade/fix their LCM I would go for it. I ordered the parts and did it myself, just because that is the type of guy that I am, but for what he charges he is really just doing it to help people out (he's not getting rich).
Hopefully I will have an update here shortly when I get everything back together.
Thanks,
Ben

[ben735]

For the headlights. From this you should/will be able to figure out where which wires go for the other relays according to the size of the holes in the pcb. 87a isnt used for the headlights and can be left unsoldered. https://uploads.tapatalk-cdn.com/20180202/7447995b4901e3323b00cc85750aeb 0c.jpg

Also, on that pic wires 30 and 86 are switched. Technically it should work either way, but just so everyone knows the center pin on the old relay is the COM terminal, which is pin "30" on a bosch automotive style relay.
Thanks,
Ben

[fastblackmerc]

Haven't had time to get everything back together and take her for a road test, but for anyone considering having fastblackmerc upgrade/fix their LCM I would go for it. I ordered the parts and did it myself, just because that is the type of guy that I am, but for what he charges he is really just doing it to help people out (he's not getting rich).
Hopefully I will have an update here shortly when I get everything back together.
Thanks,
Ben

Thanks!



12

[Keith]

If I was to buy a second LCM so that I could exchange it with my stock version at a future date, which LCM should I buy? An aftermarket or an OEM?

I'm thinking of buying one outside and then sending to FastBlackMerc so that the upgrade wouldn't have to be on an urgent basis.

Are there part numbers available?

Thanks!

Keith in Houston
Rookie - soon-to-be non-stock DTR

[fastblackmerc]

If I was to buy a second LCM so that I could exchange it with my stock version at a future date, which LCM should I buy? An aftermarket or an OEM?

I'm thinking of buying one outside and then sending to FastBlackMerc so that the upgrade wouldn't have to be on an urgent basis.

Are there part numbers available?

Thanks!

Keith in Houston
Rookie - soon-to-be non-stock DTR

I repair LCMs the day I receive them and drop it off at USPS the next day.

Any 3W7T-13C788-xx or 4W7T-13C788-xx will work.

I'll PM you more P/N's once I get home and access my spreadsheet.

[ben735]

I know this thread is quite old, but finally had to to fix everything and get it all back together. SO, just to close out...rebuilt LCM w/ new relays, replaced 20A Maxi fuse, and cleaned out a TON of corroded wires/connectors on the driver side kick panel. Hard to say exactly what fixed it, but I wasn't going to go put everything back together without repairing the corrosion. Relays in the LCM definitely looked pretty rough too.
Lights are working good now!