E39 540i electrical gremlins...

[carlito]

Hi all

Got a number of electrical problems that have started to arise one after the other recently!

I know these are great cars overall but have heard the electrics can be troublesome especially on the slightly older one's.

1) The ASC light on the dash stays constantly lit. Have heard this could be a problem on the main ASc unit?

2) The airbag light stays constantly lit.

3) Although the cruise control was working fine the last time I used it which was a good 5-6 months ago, tryed it the other day and worked for a while then stopped. (this is a problem i could live with though and may have to depend on the cost of sorting out the others!

4) The blowers on the heating system randomly turn themselves on and off intermitently?

5) One of the front main beam lamps recently stays constantly on hence draining out the battery, temporarily disconnected it for the moment.

Any advice or tips on sorting out any of the above would be much appriciated.

I do not relish the Idea of taking the car to a main dealer to be stung with massive diagnostic costs before they even can repair the faults.

I would much prefer to take it to an independant specialist on BMW fault diagnostics if anyone can reccommend one??

I know there will be a cost involved in sorting these issues out but the car will be with me for a while ferrying the family around and is immaculate in all other respects so I think It would justify the cost.

Thanks in advance for the help.

It's a 1997 model auto step.

[blackspider]

Probabely a wheel speed sensor for the ASC.

Heater resistor pack for the heater blower

Seat belt pre tensioner loom (n/s or o/s) or seat occupancy mat for the air bag

LCM control unit for the headlamp.

Cruise normally the unit under the bonnet that links via a bowden cable to the throttle-they seize

Most indies can use diagnosis equipment to find these faults-The above are by far the most common causes.

Edited by blackspider on Tuesday 12th December 08:17

Edited by blackspider on Tuesday 12th December 08:21

[off_again]

carlito said:

1) The ASC light on the dash stays constantly lit. Have heard this could be a problem on the main ASc unit?

Probably a speed sensor - a diag test should flag it up - common(ish) fault.

carlito said:

2) The airbag light stays constantly lit.

Probably the seat belt pre-tensioner wiring, or occupancy mat (driver / passenger) but also could be elsewhere. Mine failed on the wiring for the driver seat, but was easily fixed. Now its the sensors in the bumper that have rotted - need to get that fixed but reset is only possible with a proper tool. Dealers have this but you can spend £100 and get a BMW Airbag reset tool - its a bit of con....

carlito said:

3) Although the cruise control was working fine the last time I used it which was a good 5-6 months ago, tryed it the other day and worked for a while then stopped. (this is a problem i could live with though and may have to depend on the cost of sorting out the others!

Possibly linked to the wheel sensor - do check the ABS though as well as the sensor for the brake. Could be something simple

carlito said:

4) The blowers on the heating system randomly turn themselves on and off intermitently?

Mmm, puzzling - not sure. Again a good indie can do a diagnostic check to see what happens. First step though, check the fuses and check all of them - some things are cross connected so a blown or intermittent fuse can cause problems elsewhere.

carlito said:

5) One of the front main beam lamps recently stays constantly on hence draining out the battery, temporarily disconnected it for the moment.

Again, check the wiring for the lights and fuses. Might be the wiring again though - the airbag sensor for the front is just below the front lights, so it might be a cream crackered loom there. Easy to replace / renew but get it checked though.

[carlito]

Thanks for your informative replies guy's. Much approciate you taking the time to reply.

Gives me an idea of what the problems could be, what I need is a good honest indie that anyone can reccommend in the north west London or surrounding area's that can take care of them (don't mind traveling for the right place)

Would love to have a go at it myself as have reasonably good car work skills but due to work and family commitments, don't have the time.

Really need them sorted out before Xmas at least the ASC and airbag as am planning on taking the fam away in the car for a break.

can anyone help?

thanks in advance.

[J-skid]

carlito said:

The blowers on the heating system randomly turn themselves on and off intermitently?

My Dad's one did this shortly before he chopped it in. Does it only do it when in Auto mode on the climate? If so then it might be the sunshine / light sensor that increases the fan speed when in sunlight that is knackered.

Edited by J-skid on Tuesday 12th December 13:59

[windsorrob]

I've had a couple of the same problems and here were my fixes :

Heater turning on and off. Mine was the 'hedghog' resistor (also known as the final stage resisitor that controls the fan speed. There £60 new from a dealer and take about 30 mins to fix. They are sited in the centre consol but you get to them down in the drivers foowell. Do a search on BMW5.co.uk or BMWtips.com as I managed to find some pictures a guy had taken when he did this which was a great guide to the work.

The cruise control - does you speedo and mileage readings work ? I had one of the ABS sensors go and it affected the cruise control, speedo and mile readings. I think it was the rear nearside. These are a common fault on these and I've now got another one that's failed. The part is circa £55 new and I got an indie to chage it as it's fiddly to get to and they can break off meaning they need to be drilled out. Even if this happens its not a hard job with the right tools.