I have a 7.3 diesel and I have been going through alternators. I bought the truck used knowing it needed new battereis and an alternator. When the shop replaced the alternator it was a bad one and they had to put a new one in the next day. It lasted about 18 months, and then went bad. A few weeks before it went bad I got a new cd player in my truck that has a touch screen and dvd player with built-in bluetooth. Basically I have went through 3 alternators in 4 months since I've had the cd player and I dont know what is causing it. I replaced the starter because it was bad, but it seems to still be sluggish on the 1st start of the day and my I had to get jumped off yesterday. Is my cd player the cause? I only have the stock speakers and don't watch DVDs.
i seriously doubt the CD player is effecting your charging system. Even though its possible to get bad new parts. 3 alternators in 4 months tells me something else is your issue. The slow starting is because the batteries are low. Do you know if the shop went through the entire charging system or is just replacing parts and sending you out the door?
Are you getting the old alt tested before you replace it or are you assuming that is the issue? This thread http://www.ford-trucks.com/forums/10...lternator.html on post 10 has the schematic for the 7.3 charging system. check all the wires for shorts. If you have a multi meter you can check everything out yourself.
I had bad experience with NAPA rebuild alternator and reading this forum -bad alternators are pretty common. The problem with alternator testing is that bad brushes, or bad regulator can have intermittent problems for long time before giving up and my bad alternator was passing bench test with flying colors, before it die 6 weeks later.
When I had the problem, I wired good tester to the cigarette plug and was observing the voltage during driving. It could jump from 12.8 to 14.3 V in split second, while dash gauge would not move at all.
One of the problem I had on my 7.3 starting was poor connections on ground cables to the engine block. You might want to clean and recheck them.
Have someone check both batteries with a newer style conductance tester, not a load tester. A load tester just tests how much current a battery can produce--A conductance tester actually tests how fast a battery can recover from a high current draw. You have to isolate each battery from the other to test them, as they are wired in parallel. Disconnect the cables from both batteries and test them individually. You will probably find that 1 of them is bad, and that is what is killing your alternators.