Huge electrical issue with a 1997 740iL

[Reflex]

The car is a late 1996 production 1997 model year with 59K miles that sat for a while.

Air bag and brake fluid low lights are illuminated, check brake linings and low coolant messages come on the cluster, sunroof, power windows, power door locks, soft close trunk, wipers, A/C, heater, ALMOST NOTHING ELECTRICAL IS WORKING.

Also my brake pedal is soft and weak, and has to go down all the way in order to stop the car.

Checked all the fuses on the passenger firewall and in the trunk, all fine. Replaced the ignition switch, since that could trigger similar stuff when it goes bad. Again no difference. The battery is new.

Any input will be greatly appreciated. I do have a feeling that the dealer might have crossed the battery terminals into the wrong slots, which might have caused a shortage.

[Mayorchuck]

Any sign of water in the cabin? Main fuse block and splices under the passenger seat. Also check the main fuses above and forward from the battery.

- - - Updated - - -

https://www.bimmerforums.com/forum/s...nder-pass-seat

[Reflex]

Thank you for the response. Under the passenger's seat is the next destination.

BTW, these are the codes I got. Not sure if there is supposed to be more as I unplugged the battery over the weekend.

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[Mayorchuck]

Wow. I would pull the GM and check the connections for moisture as well. Check the LCM behind the passenger side kick panel as well. Can't really point at one thing though. I believe the brake pads are on one loop to the IKE. Just strange. I need to think a bit more on this one.

[Reflex]

Chuck,
Would a GM from a 2001 740iL work? I have an access to one. That would be the easiest start point for me.

[Mayorchuck]

It should. Even without coding it to your car, some functions should be restored if that is causing some of your issues. I would recommend disconnecting the battery cables when you do the swap. If it looks like water has been present in the connections, you can bet water found it's way to the fuse block under the seat.

[Reflex]

Just swapped the GMs. No water damage present. Issue stayed the same. Onto the next destination, which will be under the passenger’s seat.

[Reflex]

Found a hidden sea under the passenger's seat.

[Mayorchuck]

Good. That's the only thing that would make sense for the majority of it. Nice they picked the lowest point in the floor pan to put all the things that should not get wet!

[Reflex]

Dried and cleaned up. There were few rotten wires were out of there spot which have been fixed. Everything came back to life except the radio/MIDI and the driver's seat/steering wheel. Also the check coolant level and the brake linings messages are still present on the cluster. About to head out to bleed the cooling system since now that the heater is working. Slowly getting there

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[Mayorchuck]

Good work. I would recommend not putting the seat back in until you run down the MID issue. Could be one of the wires in a comb splice is corroded out of site. Is the side trim on the drivers seat loose? That's usually the issue with the seat/steering wheel. Brake linings should be unrelated.

[noobbiker]

Need to check your moon roof drains next. Or you’ll be repeating this job in a couple of years. Most likely source of water.

[Reflex]

Good work. I would recommend not putting the seat back in until you run down the MID issue. Could be one of the wires in a comb splice is corroded out of site. Is the side trim on the drivers seat loose? That's usually the issue with the seat/steering wheel. Brake linings should be unrelated.

The driver’s seat control unit was unplugged, thus effecting both the seat and the steering wheel. So that’s out of the way.

The MID issue is an interesting one. When I feed power to it, the MID worked and so did the radio/tape and unit as well as the DSP monitor. But won’t work on it’s own. Any idea?

Other than all of that, the car is nearly done. Cooling overhaul is coming up tomorrow. New water pump, thermostat, radiator and hoses to ensure a cooling related problem free many miles.

Oh and I had to replace the A/C compressor. It’s pulley somehow seized up on there! Put a new one on and now the A/C compressor seems be working for a minute or two and then the cold air disappears while the A/C button is still active. You can smell it too when the compressor is no longer active. I am not sure if the resistor on the fan motor is shot. The other symptom is that it won’t blow hard from the first second. It takes a while for it to raise it’s fan speed. I remember having a weird issue on my previous E38, where the passenger’s side of the dash was not blowing any air and I ended up replacing the HVAC control unit under the MID and it fixed my issue. But I highly doubt this time it’s the control unit. I am leaning towards the resistor.

Oh and noobbiker,
I will be redoing the entire headliner and the pillars in grey suede next week. Will make sure all the drains are free from any dirt and properly plugged.

[Reflex]

The car is error code free other than the airbag light on the dash. The issue seems to be the right side satellite sensor. It is a communication error. Where is it located and what is the part number for this? I searched every BMW forum I know with zero answer.

[Mayorchuck]

Never heard of a satellite sensor. Are you working on the airbag light or the MID still?

[Reflex]

Both actually. However I finally found the location of the satellite sensor. It is under the passenger's side carpet. Should have known. Got to pull the seat out again and take a trip to a local junk yard.

The MID/tape is an interesting one. When I fed power to it, it worked. But there is no power coming to it.

[Mayorchuck]

Your MID issue may very well be under the passenger seat. Double check those comb splices. Does not take much corrosion for one not to be making contact.

[alexisonfire]

Also dont forget the valley pan gasket and the 4 o rings for the pipes and the 2 rear accumulator gaskets.

[Mayorchuck]

Also dont forget the valley pan gasket and the 4 o rings for the pipes and the 2 rear accumulator gaskets.

?? Wrong thread?

[clarkitect]

?? Wrong thread?

I was thinking same thing, but looked back and see OP mentioned a cooling system overhaul in post 13. Seems like every project is a laundry list with these things.

[Mayorchuck]

Sure enough, thanks. Probably should not be browsing the forum with a hydrocodone brain.