BECM surgery attempt

This site contains affiliate links for which LandyZone may be compensated if you make a purchase.
H

Henrik97

Active Member
Posts
301
A very unfortunate series of events have led me to remove the becm from my car and open it up. It all started with a leak from the heater matrix. The constant moisture caused the car to fog up every morning, so I bought a moisture trap to help the situation while I waited for the chance to replace the o-rings. One day, as fate would have it, I knocked the damn thing over, spilling its salty contents all over the RH footwell. I cleaned out the worst of it and thought nothing more of it. Later, I noticed relays in the LH door-station clicking away erratically and that the gear selector gate and the ride-height gauge stayed illuminated after I locked the car. I also got false blown-fuse-alerts.
Obviously, this drained the battery and code-locked me out of the car. When I finally got it unlocked and running again, I started investigating and that's when I noticed small specks of moisture absorber sitting on top of the becm, each surrounded by a big droplet of water. When I wiped it down, some more of it must have dropped through one of the many openings in the becm, because suddenly there was smoke and the unmistakable pong of burnt electronics.
I decided to pull it out and open it up, only to discover a relay burnt to a crisp. The control board looks fine, but the power board has some burnt traces and evidence of salt and moisture. I have ordered new relays and will now attempt a clean and repair. If anyone has experience from working on these, I'll be grateful for any tips. Also, If someone knows what parts of the power board controls the front windows, please let me know, as I have very intermittent operation on both sides.

Wish me luck!

Henrik
 
Before you spend too much money or time you might want to talk to RICK THE PICK or IRISHROVER about either repairs or a complete BECM swap.

If you're going ahead yourself, clean the board with pure alcohol to wash all the contaminants off and dry it thoroughly.
 
Good luck!. The front window signals get to the front doors via the serial link ie from the becm to the door outstations. There are no relays for the front doors inside the becm. Strange thing is, if your front door locks work ok (also use same serial link as windows), this would indicate the becm serial link output is ok. The serial link comes from the logic board, so if the becm is causing the window problem it seems as though this will associated with a problem on the logic board (prior to the serial link output stage).
 
IF you can dry and clean it you'll be very lucky.........PCB's so complex are notorious! If you can't sort it Irish is your man for sure.........and he's back over here real soon ! :eek::eek:
 
Thanks everybody!
So, if the window is playing up but the doorlock is ok, the problem is most likely in the door outstation? It could of course be the switchpack, but i've checked it up and down and can't find anything wrong with it.
This won't be the first pcb I repair, so I know the pitfalls. I've found that a synthetic brush in a Dremel, soaked in alcohol and used carefully does wonders. The logic board seems fine, so other than some local light cleaning, I'm gonna leave it alone.
I have new relays and some spare power transistors (in case some are faulty - I don't know) coming today or tomorrow (Mouser.com are pretty great, albeit expensive). I guess we'll know how I fare in a couple of days.

regards,
Henrik
 
godd luck with the becm. with regard to the windows, try and pull the window switches apart and clean the contacts with an electrical cleaner. Although i have never repaired a range rover window switch, i have repaired many others on many makes and models witjh intermittant faults and always found it to be the switch contacts. Even though they look ok, spray with electric contact cleaner, more often than not it gets them working again.
 
spadgr said:
godd luck with the becm. with regard to the windows, try and pull the window switches apart and clean the contacts with an electrical cleaner. Although i have never repaired a range rover window switch, i have repaired many others on many makes and models witjh intermittant faults and always found it to be the switch contacts. Even though they look ok, spray with electric contact cleaner, more often than not it gets them working again.
Click to expand...

Thank you - I will try that.

Henrik
 
Update:
What I have found on the power board makes me very optimistic about getting it working again, probably better than it has for years. Here's the run-down:

- One blown relay, with associated burnt pcb tracks. I have replaced the relay and hardwired all the connections to bypass the duff pcb tracks.
- One power transistor pretty much consumed by corrosion, new one is in the mail.
- Corrosion under one of the multipin connectors had shorted out two tracks. They were 1.5Ohm, now they're up to 1.2MOhms.
- An elecrolytic reaction through moisture in one of the connectors on the logic board had eaten completely through one pin (the residue was electroplated onto the pin next to it). I'll simply bypass it with a short wire.

All these faults can explain battery drain, intermittent operation of some of the equipment and flickering lights. I hope and believe my repairs will sort it. Fingers crossed!

Henrik
 
When you have finished, if it works, take the time to spray the boards with a Conformal Coating designed for PCB's to ensure that it is protected against moisture in the future.
 
Datatek said:
When you have finished, if it works, take the time to spray the boards with a Conformal Coating designed for PCB's to ensure that it is protected against moisture in the future.
Click to expand...

That's already in the works, but thanks anyway!

Henrik
 
Hi
Well, I guess we can call it a success. It's back in the car, and all flickering lights and mysterious battery drains are gone. However, there are a couple of issues.
1: power windows seem seriously confused. It doesn't worry me too much yet, as I've seen before that it takes a few runs for all faults to clear after the battery has been out. All ideas are welcome though, so please share your thoughts.
2: This is worse. I only drove it about half a mile yesterday and then parked. When I got back to it this morning, it wouldn't crank. No faults on the display, just not a peep from the starter. Battery is good. I had a friend come over to listen for signs of life under the bonnet, and he could hear a relay clicking, so the message is obviously being sent when I twist the key. After jiggling the key for a while, listening for reactions, it suddenly fired right up. Any ideas?

Henrik
 
Henrik97 said:
Hi
Well, I guess we can call it a success. It's back in the car, and all flickering lights and mysterious battery drains are gone. However, there are a couple of issues.
1: power windows seem seriously confused. It doesn't worry me too much yet, as I've seen before that it takes a few runs for all faults to clear after the battery has been out. All ideas are welcome though, so please share your thoughts.
2: This is worse. I only drove it about half a mile yesterday and then parked. When I got back to it this morning, it wouldn't crank. No faults on the display, just not a peep from the starter. Battery is good. I had a friend come over to listen for signs of life under the bonnet, and he could hear a relay clicking, so the message is obviously being sent when I twist the key. After jiggling the key for a while, listening for reactions, it suddenly fired right up. Any ideas?

Henrik
Click to expand...

Under bonnet fuse box, ignition relay and starter relay would be a good place to start.
 
Datatek said:
Under bonnet fuse box, ignition relay and starter relay would be a good place to start.
Click to expand...

Aha! These are separate relays? I did change the one with an engine-with-lightning-bolt symbol, but that's probably the ignition. Which is the starter relay?

Henrik
 
You must log in or register to reply here.

Similar threads

I
P38 BeCM locked?
Replies
8
Views
771
pwood999
pwood999
P38 guy
P38A Aftermarket remote
Replies
1
Views
450
pwood999
pwood999
DollyBird
Engine disabled, keys not working, tried the guide “Re-synching the Range Rover P38 diesel engine with the Solved - BECM using a Nanocom” no luck
Replies
9
Views
1K
DollyBird
DollyBird
ar1g3
P38A Bulb Failure message preconditions?
Replies
6
Views
601
Datatek
Datatek
A
P38A Cruise control question ( wheel speed issue )
Replies
16
Views
1K
AndyF07
A
Back
Top