List of electrical gremlins in my '92 525i Touring

NOTE: Aftermarket remote/alarm fitted

* Central locking randomly locks/unlocks/ then locks again both when driving or with car parked and motor and ignition off and keys removed
NOTE: So far it has never unlocked by itself after being locked
* Cruise Control works intermittently If it drops out while cruising it will come back on again at the current set speed
* R/H Low Beam intermittent
* Transmission sports mode works intermittently
* Car sometimes won't start (no cranking) but eventually does after 5-10 mins
* Trip meter won't reset
* Rear wiper/washer n/w

NOTE: Left hand tailgate wiring looks cracked, I will fix this first and then see what the situation is.

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Originally Posted by pundit

NOTE: Aftermarket remote/alarm fitted

* Central locking randomly locks/unlocks/ then locks again both when driving or with car parked and motor and ignition off and keys removed

Check your battery termincals are clean and that the battery is strong. Measure the alternator output, if it is dying it will cause 12V+/ reduced conditions that will upset things like this.

Check where the 'expert' who installed the alarm/remote locking made their mess and clean up the wiring. If not that, check the 50A fuse by the battery

NOTE: So far it has never unlocked by itself after being locked

* Cruise Control works intermittently If it drops out while cruising it will come back on again at the current set speed

Check your brake light switch for perfect continuity

* R/H Low Beam intermittent
HIDs from dtmtuning.com

* Transmission sports mode works intermittently
Console switch- beware coffee/coke etc.
Connector on the side of the trans.
Connector on trans cmputer module

* Car sometimes won't start (no cranking) but eventually does after 5-10 mins
Check your auto gear lever- the starter motor cutout switch is 'cutting out'

* Trip meter won't reset
Dirty/corroded contacts- twiddle it round a bit, it will start resetting.

* Rear wiper/washer n/w
LH tailgate wiring

NOTE: Left hand tailgate wiring looks cracked, I will fix this first and then see what the situation is.

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Good luck - a bit to keep u busy there...

Check relays first, I guess - they are scattered about the car, but the first one I'd look at would be the headlight relay located in the fuse box (I think).
Cruise control could be a brake light switch going bad - at least that would be the least expensive thing to fix. next would be the switch on the column.
Just an idea - best luck.

Thanks so for the suggestions guys.

I will check the Lighting Control Module (LKM) for cracked solder joints as I had that issue with the LKM on my 535i sedan.

The cruise control is a bit weirder than what you have both suggested. It won't be the brake light switch as the cruise is not actually cancelling.

The cruise control will suddenly drop out while driving and after a minute or two (without me doing anything) will then simply resume at the speed it was at when it dropped out. If it was set say at 100kmh, and then drops out, it will suddenly resume again at 100kmh all by itself without me flicking it to 'resume' on the stalk. So it's not cancelling as such, it's just intermittantly losing power to the cruise control motor/solenoid, which means the control circuitry is not being affected.

Brake switch is also related to cruise control... if not brake switch, I'd suspect the cruise control module... overheating a resistor...

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Originally Posted by Tiger

Brake switch is also related to cruise control... if not brake switch, I'd suspect the cruise control module... overheating a resistor...

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As mentioned, it's not the brake switch in this instance that is the culprit. The cruise is not being cancelled, just intermittantly cutting in and out.