Service VME - Headlamp Dimming or Flicker

When servicing the vehicle with the VIN you entered, the following diagnosis might be helpful if the vehicle exhibits the described symptoms.

This message concerns headlamp dimming or flicker on Cadillac Seville and Deville. This condition may be caused by the startup current of various components on the vehicle. One of these components is the AIR pump. Activation of the AIR pump will cause the headlamps to flicker. It’s a rather dramatic increase in electrical current requirements that the charging system cannot react to in time to prevent the flicker. Horns are another one of these types of loads. AIR pumps are activated at the beginning of a drive cycle based upon a number of conditions. It is also activated during a drive cycle for diagnostics. The flicker, which is more of a onetime droop per motor activation, is due to the inrush current of the motor each time the motor is activated. The AIR pump may draw up to 90 amps when starting so the headlamps may flicker momentarily until the electrical system catches up. This can be complicated by the fact that there may be other high amperage accessories in use in the vehicle at the time, such as the heated seats, blower motor and rear defogger. Headlamp dimming can be demonstrated to the customer by using the Tech 2 to command the AIR pumps on and watching for the headlamps to dim. The reason for this message is that some dealers have been replacing generators to fix the headlamp dimming condition. Do not replace the generator or the AIR pump for this condition; it is normal. Thank you. This is John Woodrich, Brand Quality Manager for the Seville.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.