I have a 1999 F150 5.4l with a bad alternator and now a bad battery. Replaced the alternator yesterday, it didn't last 10 miles. What could cause this? Could a bad battery relay cause it? All help and suggestions greatly appreciated as I'm $400 in the hole and still have a truck with a lifted hood. I don't live close to a large town so parts accessability can be an issue. Thanks in advance.

 

These trucks only like Motorcraft alternators. A reman will work on occasion, but quite a few have had problems with them.

Have you checked every connection ? All the grounds, battery voltage , running voltage and so on ? Is your battery light on?

 

Yes my battery light is on. I think I have cleaned all connections and grounds have tested battery but now seems to be poor. Charged battery, no difference. Am frustrated. What is a battery saver relay?

 

You might want to chack the fuse for the alt/genorator, I replaced one on a tarus that efter being done it didn't work, because when it went out it toke the fuse with it.