1988 Ford F250 Pickup, Battery Goes Dead While Parked

This 1988 Ford F250 Came in with the complaint that the battery would go dead while sitting overnight. As soon as the truck was dropped off I checked the alternator and confirmed that it was not charging properly. It had excessive ac ripple voltage. This would not explain the battery going dead overnight but it was a definite clue. There are a multitude of ways to see if the alternator was the cause of the battery going dead overnight but I used one of the simplest methods. The customer had stated that he had charged the battery with a battery charger and did not connect the cables until he was ready to bring the truck in. I parked the truck and let it sit undisturbed for about 2-3 hours allowing the engine to cool off. I then simply placed my hand on the alternator and noted that it was much warmer than the rest of the underhood components. Diagnosis, the alternator was draining the battery while sitting. Simply put the battery goes dead because amps are being consumed. Amps equal heat.

Now that the alternator had been diagnosed as the problem it was time to replace it. The first step is to move the belt tensioner and remove the belt form the alternator.

The upper mounting bolt has to be removed by using a ratchet and short socket or a wrench.

Now the bottom mounting bolt can be loosened and removed. It is a long bolt and has to be wiggled out past the fan shroud. Once the bolts are removed the alternator can be rotated and twisted around to  free it from the bottom  bracket.

After the alternator is out of the way the spacer can be reset  so that the replacement alternator will be easier to install.

Note that this alternator  has a plastic shield attached to it. It is very important that this shield be transferred to the replacement alternator if it the same design. The shield is used to guard the fan blade and to help direct air flow through the alternator. Without this shield the alternator will not be properly cooled.

A pair of pliers can be used to remove the hold down strap. The strap is hooked over one of the alternator through bolts.

With one end disconnected the plastic shield can be removed. Then the other end of the strap can be unhooked from the second through bolt.

With the shield and strap installed on the replacement alternator, I removed the harness attaching clip. Obviously it could be removed at any time. It just happened to be at this point for me.

The old rectifier harness connector was damaged from heat cycling and had to be replaced as well. This is a very common problem for this style of what is referred to as a 2G alternator.

I spliced in a new harness connector using seamless splicing terminals and heat shrink tubing.

After connecting the harnesses to the alternator , I taped the hold down clip to the regulator wiring and reattached it to the appropriate hole in the plastic shield.

As a final step I made sure that battery was fully charged and checked the alternator with a meter. Do Not Ever Disconnect A Battery Cable While The Engine Is Running To See If The Alternator Is Charging. It is an untrue wives tale  and can cause severe damage to electronic components.

While I do my best to detail as much information as possible. There are many repairs that I have yet to document and some of you may wish to have more than I have provided. I would strongly recommend subscribing to one or both of the following data companies for further assistance. Although having an abundance of information does not guarantee an easy repair, the lack of adequate information will guarantee a failed repair!

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Do it Yourself Automobile Repair Information

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