I have a 1983 f100 which has developed a new and annoying problem. The battery loses power when parked for the day. Alternator seems fine. Engine will restart if I stop for a few minutes, but park for several hours and it won't start. Up until this week I could leave the truck parked for a week or two and it would restart with no problem. Wverything else seems fine. we did grt 10 inches of rain this week. Don't know if that could have anything to do with it. Where should I begin the trouble shooting? Thanks for any assistance!

 

The best way is with an amp meter, if not a simple test light will do, not an LED one just a cheap one with a bulb, disconnect your negative battery cable clamp the test light to the negative post on the battery and the other end on the cable or anywhere you can jam the pointy end into some thing so it stays strong. the light should barley light, slight dim maybe from radio memory ect. just to check your hooked up good open the door or turn your lights on should be real bright bulb. Then you simply start to pull fuses one at a time till that light goes out, now you know what circuit is the cause. Your going to have to do this with the door closed or tape the door switch. after the fuse block than you go to the fuse links on the solenoid, one at a time till the light goes out, also unplug the alt and take the power wire off it, if just one diode in the diode trio goes bad the alt will still charge but it will cause a draw. happy hunting, let us know how your doing the FTE boys are here to help.

 

I did notice that the alternator was warm to touch when everything else was cool. Is this indicative of diodes gone bad?

 

Yes. If you want to double check to make sure this is the problem, take the wires off the alternator and let it sit overnight, and then see if it will start ok in the morning. Be careful and tape the wires up so they don't short out on anything. It's best to disconnect the battery before you do it, and make sure to disconnect the battery before taking the alternator out.

 

Jees Dave your allover the place today

 

I wanted to eliminate the battery being bad, even though that was unlikely since it was brand new. So I jumped the truck and left it running for about 20 minutes. I unhooked the battery immediately and check the voltage. It was 12.93 immediately after, 12.64 in 20 minutes, 12.47 in about 2 hrs, 12.40 this morning. Reconnected the battery and nothing but click. Can I blame the battery? Did I mess up something in my test? It seems like it should have worked. I've read 12.40v is borderline. Any thoughts? Thanks!

 

I determined the battery was good so today decided to cut to the chase and change out the alternator. I removed the electrical connections with no problems. Removed the easy, adjustable bolt with no problem. However, as is typical, the last bolt won't come loose. Any secrets? Also, is there a tensioner for the belts? It seems like there should be, but I couldn't find anything that identified a tensioner. What all I missing? I'm so close. Thanks.

 

Some of those long alternator bolts can get stuck. You might have to get a hacksaw or sawzall and cut the bolt to get it out.

You should have two main bolts holding the alternator in place. One of them is the belt adjuster also.

 

Thanks for the reply! The adjuster bolt was easy. The other one is still in there. Trying more with it this weekend. Saturated it with PB blaster, etc, used heat but won't break free. I'm hoping for the best but it seems to be really seized!

 

The steel bolt reacts with the aluminum housing of the alternator, they really get corroded. I have had to cut them out before and then get a new bolt.