I am working on my '96 850 Turbo because I have noticed that every so often the battery will not recharge during normal driving...and I drive A LOT (40k+ per year) with this car.

My first thought was that I may have a dead cell in the battery, and that it wasn't holding a charge because of that so I took the battery out and had it tested.

It was fine...

My next thought was to have the alternator bench tested.

It was fine...

Any suggestions of where to look next?

 

Positive terminal. Do you have a volt meter?

 

Yes, I do.

What voltage am I looking for? The last time I connected my volt meter to the battery while the car was running I was reading around 12.8-13.5 across the positive and negative posts.

Should I be using the chassis ground instead of the battery posts to check this?

 

See again what you are getting. Then probe the wire before the positive terminal and see what the difference is then let me know.

 

Probably won't be able to post the results until tomorrow...I still have to put my car back together from its "alternator-ectomy"

Thanks for the direction to pursue though

 

Well...I was able to get the thing back together to test around 2300 PDT.

The voltage readings that I got were 13.5v at the battery, and 13.8v at the alternator. These reading were taken using the chassis as the ground as well as the negative post on the battery.

According to my Haynes manual, this is right on the edge of acceptable (13.5v - 14.8v) unless of course this number will vary based on the charging needs at the time.

Your thoughts...

 

Those look pretty good. 14.0 is pretty much as high as I see all the time. 13.8 is fine.

 

What are the symptons of "not recharging". Example are you going out to the car after work and it won't start? Or just stopping quick somewhere for a few minutes then car won't restart?

 

There were a couple of times that I would be out for the day and when I returned to the car it would be hard starting, but at one point my wife was sitting in the car listening to the radio waiting for me to call on a client (not realizing that she had the key in the 2nd position) and we had to call AAA to get the car started for the return trip home.

This trip home was over 50 miles of highway driving so I didn't think much of it but the next morning I went to leave for work and there wasn't enough juice in the battery to do anything...at all.

This is the second time my wife has done this to this car, and I did have to replace the battery the first time, mostly because it was a 50 month battery that was roughly 7 years old so it was due anyway.

This is when I started looking for the why and testing the charging system.