Battery or alternator problem?
Thread Starter
Le Mans Master
Joined: May 1999
Posts: 6,692
Likes: 29
From: Texas
Battery or alternator problem?
Yesterday driving home I noticed by alternator guage was pushing just under 18 volts charging. Car temp guage also kept showing about 210 or more temp though I know car was not hot. Thought the coolant temp sending sensor might be acting up so made sure it was connected properly, which it seemed to be. Today, on way to work, temp guage acting properly - 195 or less. But the battery light is now on and guage shows just under 13 volts. What is going on? Bad alternator - its only three years or so old. Battery problem - its only two years old - an Interstate.
Burning Brakes
Joined: Dec 2008
Posts: 971
Likes: 45
From: Middlesex NJ
Sounds like a flaky regulator in the alternator. Clean up all your grounds also.
Ive seen a bad regulator freak out the coolant gauge. The second you start driving and accelerating your temps will climb through the roof at an impossible rate and then when you slow down and stop (ex. engine idling) your temps will suddenly cool down immediately which is simply not possible.
Turns out the regulator was putting out 18-19 volts above idle and the temp gauge was being fooled by the higher than normal voltage.
Ive seen a bad regulator freak out the coolant gauge. The second you start driving and accelerating your temps will climb through the roof at an impossible rate and then when you slow down and stop (ex. engine idling) your temps will suddenly cool down immediately which is simply not possible.
Turns out the regulator was putting out 18-19 volts above idle and the temp gauge was being fooled by the higher than normal voltage.
Guessing that you lost a belt or it is slipping badly and not turning fan/alternator.
Drifting
Joined: Mar 2011
Posts: 1,271
Likes: 1
From: PA
Thread Starter
Le Mans Master
Joined: May 1999
Posts: 6,692
Likes: 29
From: Texas
Turns out it was a bad alternator - NAPA reman. But got a replacement for free under lifetime warranty.
It was doing exactly what mysixtynine said. Start driving and it goes to almost 220 degrees. Stop at a light and its 195. No way 220. Regulator must have been bad as it was showing the 18 volts. Thought the thing was going to blow that battery!
Of course, you have to take the NAPA alternator apart and rotate sides about 60 degrees to get everything lined up correctly. And, when you take it apart, the bushings and springs pop out and you have to struggle with needle nose pliers, paper clips and holding your tongue just right to get it all back together - about an hour task.
Then the old battery ring terminal decided to snap off after 29 years and that is another trip to the store to find the right terminal.
Anyway, all is well now.
It was doing exactly what mysixtynine said. Start driving and it goes to almost 220 degrees. Stop at a light and its 195. No way 220. Regulator must have been bad as it was showing the 18 volts. Thought the thing was going to blow that battery!
Of course, you have to take the NAPA alternator apart and rotate sides about 60 degrees to get everything lined up correctly. And, when you take it apart, the bushings and springs pop out and you have to struggle with needle nose pliers, paper clips and holding your tongue just right to get it all back together - about an hour task.
Then the old battery ring terminal decided to snap off after 29 years and that is another trip to the store to find the right terminal.
Anyway, all is well now.
