HEADLAMP HIGH BEAM RELAY
DESCRIPTION
The headlamp high beam relay is a conventional International Standards Organization (ISO) micro relay. Relays conforming to the ISO specifications have common physical dimensions, current capacities, terminal patterns, and terminal functions. This relay is contained within a small, rectangular, molded plastic housing and is connected to all of the required inputs and outputs through five integral male spade-type terminals that extend from the relay base plate.
The headlamp high beam relay is located in the Junction Block (JB). This relay is omitted from vehicles equipped with the Daytime Running Lamps (DRL) option, which have a DRL solid state relay installed in the JB that also performs the high beam relay function.
The headlamp high beam relay cannot be adjusted or repaired and, if ineffective or damaged, it must be replaced with a new unit.
OPERATION
The headlamp high beam relay is an electromechanical switch that uses a low current input from the Body Control Module (BCM) to control a high current output to the headlamp high beam filaments. Within the relay are an electromagnetic coil, a movable contact and two fixed contact points. A resistor is connected in parallel with the coil, and helps to dissipate voltage spikes and electromagnetic interference that can be generated as the field of the relay coil collapses.
The movable common supply contact point is held against the fixed normally closed contact point by spring pressure. When the relay coil is energized, an electromagnetic field is produced by the coil windings. This field draws the movable contact point away from the normally closed contact, and holds it against the normally open contact. When the relay coil is de-energized, spring pressure returns the movable contact back against the normally closed contact.
The inputs and outputs of the headlamp high beam relay include:
- Common Supply Terminal (30) - The common feed terminal is connected to a fused B(+) circuit at all times.
- Coil Ground Terminal (85) - The common feed terminal is connected to a fused B(+) circuit at all times.
- Coil Battery Terminal (86) - The coil battery terminal is connected to a control output of the Body Control Module (BCM) and to the momentary optical horn (flash-to-pass) output of the multi-function switch through a high beam relay control circuit. The BCM or the multi-function switch controls headlamp high beam operation by controlling a ground path through this circuit.
- Normally Open Terminal (87) - The normally open terminal is connected to the headlamp high beam filaments through the high beam relay output circuit and provides battery voltage to the headlamp high beams whenever the relay is energized.
- Normally Closed Terminal (87A) - The normally closed terminal is not connected in this application, but will have battery voltage present whenever the relay is de-energized.
The headlamp high beam relay as well as the hard wired inputs and outputs of the relay may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information.
REMOVAL
WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental restraint system before attempting any steering wheel, steering column, airbag, occupant classification system, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the supplemental restraint system. Failure to take the proper precautions could result in accidental airbag deployment.
NOTE: The headlamp high beam relay is installed in the Junction Block (JB) on the driver side outboard end of the instrument panel. Vehicles equipped with a Daytime Running Lamps (DRL) relay MUST NOT have a headlamp high beam relay installed in the JB.
1. Disconnect and isolate the battery negative cable.
2. Remove the trim from the driver side end of the instrument panel. (Refer to 23 - BODY/INSTRUMENT PANEL/INSTRUMENT PANEL END CAP - REMOVAL).
3. Remove the high beam relay by grasping it firmly and pulling it straight out from the receptacle (2) in the Junction Block (JB).
INSTALLATION
WARNING: To avoid personal injury or death, on vehicles equipped with airbags, disable the supplemental restraint system before attempting any steering wheel, steering column, airbag, occupant classification system, seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the supplemental restraint system. Failure to take the proper precautions could result in accidental airbag deployment.
NOTE: The headlamp high beam relay is installed in the Junction Block (JB) on the driver side outboard end of the instrument panel. Vehicles equipped with a Daytime Running Lamps (DRL) relay MUST NOT have a headlamp high beam relay installed in the JB.
1. Position the headlamp high beam relay to the proper receptacle (2) in the Junction Block (JB).
2. Align the high beam relay terminals with the cavities in the JB receptacle.
3. Push firmly and evenly on the top of the high beam relay until the relay base is fully seated in the JB receptacle.
4. Reinstall the trim onto the driver side outboard end of the instrument panel. (Refer to 23 - BODY/INSTRUMENT PANEL/INSTRUMENT PANEL END CAP - INSTALLATION).
5. Reconnect the battery negative cable.