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Post by valhalla on Feb 16, 2023 0:03:52 GMT 1
Well, having dealt-with the DDM on this car, the next problem was to try and sort-out the errant F/O/S foglamp - the unit was renewed, but the owners said it didn't work.
The problems started with the fact that nothing worked, at all, on the Light Switch Control (LSC) unit to the right of the steering wheel. So diagnosing the foglamp was not possible until I could make the lighting functions work.
The module itself was good for powers and grounds, and something seemed to be happening on the LINbus, both ways, but I suspected that this module was still faulty - a PowerProbe scope is only so good for establishing a good communication between modules, not interpreting that information off any of them. Given that nothing was happening, and the Central Control Module on the dash fuse/relay plate over the pedal was all in good shape, I decided to strip the LSC down;
Something horrid had gone through the rheostat thumbwheels, and rotted the circuitboad right out;
This is more than most of the online information for this module seems to cover; most problems with this are down to dry-joints. I had to clean the module completely around the L/H of the two rheostat sliders, and particularly underneath it, to remove all the ferrous materials from the circuits. At that point, it was clear that the rot was more than just "rust" bridging things out - the board itself was damaged around the track and via (through-hole) that handles the signal off this rheostat, and I think this had been bridging also to the main power feed through the board nearby.
I did some of the most intricate circuitboard repair I have ever done, in my life. This involved threading raw copper stranding down through the damaged via area, and making good connections to the via-pad on the rear of the board (which was OK) and the broken track that was just visible under the rheostat potentiometer. The via hole diameter is little more than 0.2mm - the size of copper thread I used - and the track-width on the top of the board was approximately 1/3rd of the width of my copper wicking-braid. So I was working on fairly high magnification on the microscope, just to be able to see where the solder was going under the rheostat.
I'm glad to say, after 2hours of work, that complete success (well, almost complete.....a backlight bulb refuses to light 100%) was attained on this module, and I can now operate all the lighting functions over the LINbus, and thus move on to the next stage of this car's electrics......
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Post by rhyds on Feb 16, 2023 0:09:36 GMT 1
Could someone have maybe used something a bit too powerful as a cleaning/COVID disinfection spray?
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Post by valhalla on Feb 16, 2023 2:23:57 GMT 1
Could someone have maybe used something a bit too powerful as a cleaning/COVID disinfection spray? It's possible - I don't know for sure.
My first guess would be a sugary drink. In my experience, nothing kills interior electrics faster than either sugared-up coffee or Coke (TM). For this reason, I'm absolutely fastidious about keeping picnics away from the consoles on my own cars. However, I see car designs that utterly defeat all logic, and all common-sense, and one of these is......wait for it, it's a common moan of mine......
.....yes, once again, prime position for "P***s of of the Year Award" goes to the Landrover T5 platform designer/s. Drinks-holders in centre console, poor designs at that, so the cups/mugs don't fit, whatever shape and size they are, right next to the EPB electrical switch. I have a box full of failed EPB switches from the L319 Disco3/4 and RangeRoverSport vehicles I have repaired over the years. Every one, sticky sugar residue has killed them. Why I keep these, I don't know. Maybe I just like to feel angry, every so often, I don't know.
There's no drinks holder near this Volvo Lighting Switch Module, but it is easy enough to imagine a can of fizzy drink, freshly agitated by a spirited-drive over the Highland road network, depositing its contents under aerosol-pressure as the ring is pulled, and pressure-washing the whole of the dash.
Another theory, and one that fits with the failed DDM (Window Regulator Motor, et. al.) is that water has come in through the open window, and blown straight into this unit that sits next to the door front edge. The rustiness of the debris around the LH of the two rheostats could well just be that they are not designed to be exposed to water, and the steel cans have gone back to nature.
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Post by givusaclue on Feb 16, 2023 18:36:02 GMT 1
if you're prepared to go to that extreme, is it not worth buying a good s/hand one & cloning the eeprom? plug straight in & work then
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Post by valhalla on Feb 16, 2023 23:16:07 GMT 1
if you're prepared to go to that extreme, is it not worth buying a good s/hand one & cloning the eeprom? plug straight in & work then I thought about going the secondhand-route, and that was/is always the fallback solution if my repair fails. The fact that it has all come to life is proof enough that it's worth trying to source one of these. They seem to be becoming rarer....
The module itself is plug-and-play, there's no encoding on this one, you just unplug the 3-pin connector from the back, and pop a new one in.
Having fixed the module, I was able to squeeze the last bit of electrical repair onto this car today, the foglamp on the offside of the car, before I put it out of the workshop for a few days (I'm waiting on lots of mechanical bits for this car, but that's another tale....). Fortunately, the foglamp repair was much easier that this Lighting Control Module and the DDM - a bulb was missing!
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