5.0 charging issues

[mickpep]

I have a good battery, a brand new starter and alternator. First start of the day, the car starts good. While running, the volt meter settles at 12V after the engine has settled at 750~ RPM. When the engine is revved the meter shows 14V.
Once the car is up to temp, and we shut the car off it won't restart. It cranks very slowly because the battery is low, below 12V. It seems as if there is a draw off of the battery during running the car.

[michael everson]

Sounds like the alternator is not charging properly. Your voltage gauge should read around 14 even at idle. Any chance you have underdrive pulleys? That could contribute to the problem.
Mike

[mickpep]

Sounds like the alternator is not charging properly. Your voltage gauge should read around 14 even at idle. Any chance you have underdrive pulleys? That could contribute to the problem.
Mike

Thanks Mike. Yes we do have underdrive pulleys, but they were on the engine when we purchased the donor Mustang and it ran with no problems. We're going to pop the alternator out and go back and have it tested.

[seagull81]

Are you sure the battery is low? My underdrive pulleys have it charging at 12.5-13 at idle and 14.5 running. I have not had any trouble with this set up. You should have a large ground wire from one of the starter bolts to the frame?

[mickpep]

Are you sure the battery is low? My underdrive pulleys have it charging at 12.5-13 at idle and 14.5 running. I have not had any trouble with this set up. You should have a large ground wire from one of the starter bolts to the frame?

Mike, we did have a bad alternator. When we went back for another we had them test the new one before we left and it was bad too. We had to go to another store and finally got one that tested good. It seems to be working now. Our readings are about the same as yours now.
Thanks very much for your help!