Here is a stumper for Hyundaitech.
2002 XG350 with 36000 miles. Chicago, IL area. 20 degrees F this morning. 40 degrees F now. Driving home yesterday in the cold and dark with lights on including fog lights, heater, heated seat, radio and wipers intermittent. Battery icon and brakes icon both glowed briefly then went out. Did not reappear for the remainder of drive home.Started car and drove to work this morning. Headlights were on auto and never went out by themselves even though it appeared to be plenty light enough to automatically turn them off. Lights, heater, radio, heated seat all on. After 20 minutes of driving while stopped at stop sign upon accelerating from stop the battery icon, brakes icon, ABS icon and TCS icons all lit and stayed lit. I drove to Hyundai but they were on holiday hours and unable to assist. The service manager guessed at an alternator?
No Hyundai locations are able to assist until after the holiday so I took a chance and drove it home after finishing work. Upon starting the car up no icons were lit and the car drove normally. Everything seemed to work fine. I tried to get it to do it again by turning everything on including the rear window defogger. After several minutes of this while driving the same icons as before lit, battery icon, brakes icon, ABS icon and TCS icon. Once they lit I noticed the rear window defogger was no longer lit. I also noticed the speedometer was locked at about 10mph and would not move, the tach worked normally. Upon pressing the rear defogger switch it would not work (no light on the switch). I turned everything unneeded off (headlights, heated seat, radio) and drove home. All icons stayed lit until all the way home. Once in the garage I popped the hood and checked the voltage at the battery, which read well over 17 volts. Upon turning on the headlights it dropped to about 14.5 volts. Once the car was stopped and in park I noticed the ABD and TCS icons were no longer lit.
Any ideas? It sounds to me like the alternator but the voltage outputs actually seem high.