URGENT HELP!

RedOctober - again a brilliant read - totally agree with you on the electrical soldering issues - My job is a telephone engineer and spent many a day soldering/fixing bad soldering joints (Also chipped about 20 or so PS1's ) - going back a few years now!

I had service light issue on my 316 where I could have sorted the batteries out but never got round to it. Although not all E34's have the battery under the rear seat my 530 V8 did, and had a fuse blow (passenger side) which stopped the central looking and windows working (can't remember which one) but a quick replace under the rear seats fixed this.

Halfrauds are silly prices - if your going to replace them all are you going for cheapo or decent/expensive?

Anyway lots of points there and again like I've told you, you should write a book !

I never looked at pixel-fading problems, as my cars were all the older ones that didn't have displays with pixels-apart from the 3 E34's I've had with the head-up dash display, and they were never a problem in the E34's I owned.

I've had failing speedo's, failed ECU's, intermittent central locking, failed E34 instrument cluster, the good old E28/E30 NiCad service indicator battery problems, intermittent relays, failed central locking etc.

My first ever BMW was an E30 325i, and that died on me one day, requiring breakdown recovery home. The AA checked for a spark at the coil (present), but when he plugged a small 'noid light' into the fuel injector connectors on the inlet manifold, there was no output, so he diagnosed failed ECU and towed me home.

I removed the ECU, opened it, and saw 2 circuit boards. One contained the low-power components, ignition/fuelling EPROM maps etc, and the second board contained the high-power output transistors which actually drive the ignition coil and fuel injectors.

I noticed on one of the output transistors a fractured solder joint on the PCB, so I re-made the joint with a soldering iron, went over all 'fragile' looking joints, and re-fitted the ECU. The car fired up fine, and was fine for the next couple of years before I px'd it for a 635CSi.

Another 325i had a failed speedo, so I removed the instrument cluster and discovered a failed solder joint on a capacitor that coupled the speedo signal from the sensor on the final drive to the speedo PCB. Again, re-making the joing fixed the problem.

One problem I've noticed is that the solder joints seem to have been made using the minimum amount of solder, which leads to a mechanically weak joint that can fail in later life, especially with the constant heat, cold, and vibration in a car.

I had a main ECU relay go intermittent on an E30 318i (M40 engine) which would cause sudden engine cut-outs. It wasn't the usual fuel pump relay either-that was ok! The ECU relay contacts had glazed over, shutting off the ECU. I opened up the relay and rubbed very fine Wet-or-Dry across the relay contacs, which cleaned them and cured the fault.

Most of the faults cost nothing to repair-just time and effort. In general, electronic components themselves are very reliable and rarely fail unless overloaded with power etc.

What almost always causes the problems are contacts, plugs, connectors etc. Water ingress can corrode electrical contacts, leading to intermittent failures, especially in door wiring harnesses, which are subject to mechanical vibration and water ingress, causing problems with central locking and electric windows/mirrors, not to mention the constant flexing of the wiring harness each time the door is opened-if you look carefully, you'll see the harness 'staggered' as it goes from the door itself to the door pillar, to minimise this flexing.

Even a carelessly installed stereo can cause havoc with dashboard wiring harnesses. A common fault when fitting car stereos is to just bunch up the excess wiring and force the stereo into the dash.

On many BM's, there is hardly any spare clearance behind the dash, so what happens is the metal sides/corners of the stereo chafe and break the wiring behind the dash, causing all sorts of problems.

So don't let any old Joe fit a stereo to a BMW! If you are doing it yourself, make sure excess cable is neatly arranged below the level of the stereo before you push it all the way into the dash.

In extreme cases, with exceptionally ham-fisted installers, it has been known for a stereo to be pushed into the dash with so much force that it has cut clean through the vehicle wiring harness behind the dash.

I work in the electronics repair industry on aviation equipment, and see all kinds of faults in my line of work, many of which could have been avoided with a bit of care!

On the subject of missing pixels, this can be due to poor contact between the display edge and display driver panel. Sometimes, depending on the mechanical layout, you can wedge bits of cardboard in to 'force' the display panel onto the driver panel and improve contact, but it's not an exact science and can be down to luck of the draw.

E34's, and many modern BM's, are stuffed with fuses and relays all over the car. If you remove the rear seat squab base on an E34 (it just lifts up with a sharp tug at the front edges), you'll see the main vehicle battery on the drivers side, and a large box of fuses and relays on the passenger side, as well as the main fuse and relay box under the bonnet, and yet more relays behind the glove box etc!

The E34's have a headlight control module in the main underbonnet fuse box, and this is stuffed full of small relays soldered to a PCB. I once had an E34 535i with intermittent dipped beams, which turned out to be (again) fractured solder joints in this module. Re-soldering them effected a complete cure, although it took a while to locate the fault, which is the main bugbear with electrical faults, especially the truly hateful intermittent ones, which are truly a nightmare to locate.

So next time a garage tells you that you need a new ECU/Control Module costing hundreds, the reality is that they send your failed module for repair, where a technician will almost certainly effect a repair costing very little. The components that have failed will be replaced, and will probably not cost much at all if they're standard power transistors etc. They will be 'known' faults, so ample spares will be stocked, and failed joints will be re-soldered for very little cost, whilst you get presented with a ridiculous bill for a new Control Unit.

Even when complex switchable autoboxes fail, it's not always the mechanical parts failing-electrical glitches can cause the problems as well, especially on the main electrical plug that connects the autobox to it's dedicated ECU, as this lies underneath the car, and exposed to all the elements/vibrations etc.

Some sort of working knowledge of electronics is extremely helpful for BMW ownership, as even the very old ones were much more electrically complicated than equivalent Fords or Vauxhalls of the day. BMW nailed their flag of allegiance to 'Servant Sparks' long before other car manufacturers.

I once had another E30 325i where the previous owner had lived in Hungary and changed the headlamps for Europe. When I went for an MOT the tester told me the headlamps were pointing the wrong way, and had the car been abroad?

I sourced a set of UK headlamps and set about fitting them. Turns out the last owner had fitted the European spec headlights and wired them by just twisting the wire ends together to the loom and using a bit of insulation tape-I was able to pull them apart with my fingers!

Not good on a joint carrying around 5 Amps-fire hazard just waiting to happen. I used inline solder joints and heatshrink tubing to wire in the UK headlamps, then loomed the wires neatly. Not a quick job, though, but then doing things properly never is...

Alex

Yes RedOctober, you are correct, it was an original fuse so about 13 years old. My first thought was that the fuse was just old (well that was my hope as I dreaded anything else being the cause of the fuse blowing!) I may change all the other original fuses (must be about 40 or so!) with brand new ones, just to be sure. May save a headache in the long run!

Cheers for all the input chaps I live to drive another day! Another great reason for this great forum!

Mike

Glad you got it sorted - thanks for keeping us update

they may in the spare tyre, maybe handy for road rage incidents too.

Not that i recommend such actions of course....

You like your nails!!!!!!!!!!

perhaps we should start a bmw survival kit to insert in to the tool box in the boot. A nice set of B&Q assorted nails, all different lenghts and thickness. This should ensure we have the ultimate driving experience. As long as they dont get in the tyres

good news, Mike.

You have reason to smile, it cost nothing but a fuse!!!!!!!

and now you can do donuts in the snow tomorrow..........cant wait!!!

Please report your findings on this as my e39 was doing the exact same thing - I checked the maf, cleaned the other bits near to this - even put a Wynnes injector stuff after I filled it up (waste of a fiver)

Sold the car over the weekend (few) - but told the dude about the fault.
If you revved the engine it seemed fine, it you revved it slightly/quick it would then go lumpy and cut out!

BTW - I'm driving to glasgow tomorrow, 230 miles - should be interesting

LOL@ exharper! yes but I still have works van to try and drive!

I'm about to battle minus 1 now and try a few things. Wish me luck!

I'll report my findings.

 

Mike