BMW:: 5th E28/E34 series:: Start of the engine from an auxiliary source

1.1.6. Start of the engine from an auxiliary source

Start of the engine from the auxiliary power supply will help you to overcome difficulty, but you should find out and remove first of all the cause which led to a battery discharge. There are three possible reasons:

The battery sat down as a result of often repeating attempts of start of the engine or as a result of leaving included lighting fixtures for a long time.
Incorrectly the system of a charge functions (the driving belt of the generator weakened or is torn off, conducting of the generator is damaged or the generator does not work).
The battery is faulty (low level of electrolyte, battery service life expired).

At start of the car from an auxiliary source it is necessary to observe the following precautionary measures:

Before connection of the auxiliary battery make sure that ignition is switched off.
Make sure that all electric loadings are disconnected (lighting fixtures, a heater, screen wipers, etc.)
Make sure that the auxiliary battery has the same rated voltage, as sat down in the car.
If start is made from the battery installed on other car, cases of both NOT cars HAVE TO HAVE a common ground.
Make sure that transmission is in neutral situation (or of situation "P" in case of AT).

Scheme

PERFORMANCE ORDER

Connect one end of a red wire from a set for start of the car from an external source to positive () the plug of the sat-down battery.
Connect other end of a red wire to positive () the plug of the auxiliary battery.
Connect the end of a black wire from a set to the negative plug of the auxiliary battery.
Connect other end of a black wire to the bolt or an arm of the block of the engine of the faulty car rather remote from a battery installation site.
Make sure that wires do not concern blades of the fan, driving belts or other moving elements in a motive compartment.
Start the engine from the auxiliary battery, then, having left it working at single turns, disconnect wires, working in the sequence, the return to their accession.

Connect wires from a set for start of the car from the auxiliary power supply in the order shown in the drawing (pay attention that the negative wire of NOT auxiliary battery is attached to negative Clem of the sat-down battery).