Join Date: Mar 2017
Location: Chicago area
Feedback Score: 0 reviews
Low voltage new alternator new battery
1994 Acura Integra GSR 288K miles. Iím the original owner, 23 years.
Iím posting this because I could never find anything with the same symptoms and a definitive solution. The symptoms were that after about 15 minutes of driving from cold the voltage would drop from normal (14+ V) to about 12.2V and the battery light did not come on. Also there was rough running at idle. If the RPMs were above 3500 then the voltage would return to normal. If I turned off the car and restarted it the low voltage would happen immediately. Switching accessories on and off did not change the voltage more than a few tenths. The battery was a couple months old and the distributor coils were replaced about 6 years ago. This seemed like the voltage regulator in the alternator going bad, failing when it got hot. So I replaced the original 23 year old alternator but the same thing happened, after 15 minutes the voltage dropped. Reading various posts people suggested that it could be bad grounds or even a problem with the ECU. Since I have a spare ECU I swapped it but same problem. The grounds, positive from alternator and to starter all looked good. Another post suggested the changing the distributor cap and rotor. Didnít seem like it was related but they were close to their 60K mile service interval. The old ones did have wear but nothing horrible. However, this fixed the problem, no more low voltage. I really donít understand why it fixed the problem. My wild guess is that the old distributor cap and rotor were pulling too much load causing the voltage regulator in the distributor to over heat and switch off. If anyone has a better explanation I would like to hear it.
I installed the volt meter about 2 years ago so if this happened before I would have only noticed the rough idle. Which had certainly happened before and the distributor cap and rotor would have been changed to fix it.