Electrical Precautions
Electrical Precautions
General
The following guidelines are intended to ensure the safety of the operator while preventing damage to the electrical and electronic components fitted to the vehicle. Where necessary, specific precautions are detailed in the individual procedures.
Equipment
Prior to commencing any test procedure on the vehicle ensure that the relevant test equipment is working correctly and any harness or connectors are in good condition. It is particularly important to check the condition of the lead and plugs of mains operated equipment.
Polarity
Never reverse connect the vehicle battery and always ensure the correct polarity when connecting test equipment.
High voltage circuits
Whenever disconnecting live ht circuits always use insulated pliers and never allow the open end of the ht lead to contact other components, particularly ECU's. Exercise caution when measuring the voltage on the coil terminals while the engine is running, high voltage spikes can occur on these terminals.
WARNING: - VEHICLES FITTED WITH BI-XENON HEADLAMP BULBS:- The following wiring precautions must be observed. Failure to comply may result in exposure to ultra violet rays, severe electric shock, burns or risk of explosion.
- Safety goggles and gloves must be worn.
- Ensure that headlamps are switched off before removing bulbs.
- Do not touch the glass portion of the bulb.
- On no account should headlamps be switched on with the bulb removed from the headlamp.
- Bulb testing may only be carried out with the bulb filled in the headlamp.
- Bulbs must be disposed of in accordance with local authority bye-laws.
Connectors and harnesses
The engine compartment of a vehicle is a particularly hostile environment for electrical components and connectors:
- Always ensure electrically related items are dry and oil free before disconnecting and connecting test equipment.
- Ensure disconnected multiplugs and sensors are protected from being contaminated with oil, coolant or other solutions. Contamination could impair performance or result in catastrophic failure.
- Never force connectors apart using tools to prise apart or by pulling on the wiring harness.
- Always ensure locking tabs are disengaged before disconnection, and match orientation to enable correct reconnection.
- Ensure that any protection (covers, insulation etc.) is replaced if disturbed.
Having confirmed a component to be faulty:
- Switch off the ignition and disconnect the battery.
- Remove the component and support the disconnected harness.
- When replacing the component keep oily hands away from electrical connection areas and push connectors home until any locking tabs fully engage.
Battery disconnection
It is imperative that the key is removed from the ignition before disconnecting the battery. A time of 2 minutes must also elapse before disconnection. Failure to do so could result in:
- Navigation computer hardware damage.
- Incorrect fuel gauge reading.
Before disconnecting the battery, disable the alarm system and switch off all electrical equipment. If the radio is to be serviced, ensure the security code has been deactivated.
CAUTION:
- Never disconnect the battery with the ignition switched on.
- To prevent damage to the navigation computer hardware, a waiting period of two minutes must elapse after the ignition is switched off before the battery leads are disconnected.
- To prevent damage to electrical components, always disconnect the battery when working on the vehicle's electrical system. The ground lead must be disconnected first and reconnected last.
- Always ensure that battery leads are routed correctly and are not close to any potential chafing points.
After re-connecting the battery, the steering wheel must be turned to full LH and RH lock (with engine running). This allows the DSC system to relearn the steering wheel position. Failure to do so will result in a variety of instrument warning lights being illuminated.
Battery charging
Only recharge the battery with it removed from the vehicle. Always ensure any battery charging area is well ventilated and that every precaution is taken to avoid naked flames and sparks.
Ignition system safety precautions
The vehicle's ignition system produces high voltage and the following precautions should be observed before carrying out any work on the system.
WARNING: Before commencing work on an ignition system, ensure all high tension terminals, adapters and diagnostic equipment are adequately insulated and shielded to prevent accidental personal contacts and minimise the risk of shock. Wearers of surgically implanted pacemaker devices should not be in close proximity of ignition circuits or diagnostic equipment.
Disciplines
Switch off the ignition prior to making any connection or disconnection in the system to prevent electrical surges caused by disconnecting 'live' connections damaging electronic components.
Ensure hands and work surfaces are clean and free of grease, swarf, etc. Grease collects dirt which can cause electrical tracking (short-circuits) or high- resistance contacts.
When handling printed circuit boards, treat with care and hold by the edges only; note that some electronic components are susceptible to body static.
Connectors should never be subjected to forced removal or refit, especially inter-board connectors. Damaged contacts can cause short-circuit and open- circuit fault conditions.
Prior to commencing test, and periodically during a test, touch a good vehicle body earth to discharge static charge. Some electronic components are vulnerable to the static electricity that may be generated by the operator.
Grease for electrical connectors
Some under bonnet and under body connectors may be protected against corrosion by the application of a special grease during vehicle production Should connectors be disturbed in service, repaired or replaced, additional grease should be applied: Part No. BAU 5811, available in 150 gm tubs.
NOTE: The use of greases other than BAU 5811 must be avoided as they can migrate into relays. switches etc. contaminating the contacts and leading to intermittent operation or failure.