2007 Other Hyundai Models Voltage drop causes Headlights to

I have a 2007 Hyundai Azera Limited with the Ultimate package. This vehicle has been at the dealership service department three times for a voltage drop problem. The main symtom is that all exterior and interior lights dim for about one second when reducing speed. I measured the voltage drop with an analog VOM and saw a 1.1 volt drop occur between 1050 and 1150 rpm. This occurs only when moving, never when sitting and reving up and down through this rpm range. I tested with the AC on and off and the result is the same.

On the first trip in for service the dealer said they could not duplicate the problem. They did not test using a VOM. They did replace the battery due to a low starting voltage. Lights continued to dim. At the dealer for four days this trip.

On the second visit I provided the results of my tests. They kept the car for four days and managed to fix the problem by cleaning all of the grounds. The fix was temporary because the dimming headlihts returned after 1,000 miles.

The third trip in for this problem was fustrating. They kept the car for four days again. This time they informed me that they would not be able to fix the problem, because everything is working as designed and within tolerances, per Hyundai. I also had an ABS wheel sensor replaced under warranty during this visit.

Two days later the car is once again in the shop for the same ABS problem, same wheel. They once again have had the car for four days. They say they are having a problem determing why the ABS sensor is indicating bad.

I think my first problem is with the Hyundai service department at my delear. Seems there standard repair time is four days.

Do you think the voltage drop and ABS problem are related? I think there is a speed, or rpm sensitive device causing the voltage drop.