1994 Ford Mustang Voltage Drop while running

JUANERDZ

MEMBER
1994 FORD MUSTANG
V8
2WD
MANUAL
39,000 MILES

I have a 1994 Mustang GT with 39,000 Miles. The Problem started about 7 years ago with about 30,000 miles. The car used to have a high power amplifier installed. Once while the car was idling and the stereo was at medium volume I noticed a voltage drop on the Dashboard (from the usual 13-14 to about 10). The car remained on. After that when I would start the car the voltage would be fine but as the day would go along it would start to drop. I would brake and the needle would drop to about 10. The more lights I had on the more it would drop. Revving the engine made it rise. I could also hear a whine coming from the rear of the car. I had my alternator checked and they insisted it was fine but I decided to replace it anyway. I also completely removed the stereo system. These didnt help and the symptoms persisted. I dont drive the car too much and to this day it still behaves the same way. Starts up fine but the longer the engine is running, the voltage starts to drop and the whine from the rear can still be heard. I've thought about replacing the wiring from battery to the rest of the vehicle and maybe the alternator wiring as well considering its 14 years old. I figure it might be heat resistance thats the problem. What do you think?

1 Reply

MASTERTECHTIM

MECHANIC
4,750 POSTS

I would start by checking battery cables at the battery and engine. ** Check the battery cable ends at the battery. A lot of times high resistance builds up where the cable is molded to the terminals. I usually cut off the ends and wire in universal ends from the parts store. Hope this helps. Also check voltage at the battery while running and see what it is, also check voltage at the fat red wire at the back of the alternator.