Hello ladies and gentleman,
I have a 1988 Ford F150 Lariat XLT 5.0 EFI. Here recently I have started having an electrical issue. The truck would start and run, and would charge at 14 volts like normal. However when I was returning home the other day, I was making a turn onto my road and had my blinker on. The voltage gauge went all the way down to 8 volts. I revved up the engine and it came up a little. Once the ticker went off the voltage came back up. Later that week it got really bad when I was using the defroster and the voltage never got above 9 volts til I turned the fan motor off. I took it in to advance and the hooked it up to their tester and everything came back normal except the voltage reading was up and down like crazy. I would like to cure this issue please. I need my truck to get back and forth to work. Any ideas?

 

If your alternator doesn't have steady voltage in the correct range it failed the test. As did whoever was doing the test.
Pretty much the whole point of testing an alternator is to see if its putting out steady correct voltage.
It is possible to test the amperage output (current) as well, but if your voltage output isn't correct, your amperage won't be either, so I'm not sure
what could be "normal" about your alternator.

 

I talked to a friend of mine and he said its possible that the EEC IV is possibly going bad, is that a possiblility?

 

Wouldn't you want to check the voltage regulator first? If you took the alternator into the place and the voltage was up and down like crazy, how does that relate back to the PCM?

 

As far as I know, there is no voltage regulator on my truck, it is an EEC IV unless somebody else knows where it is located, never found one.

 

You have an internally regulated alternator. Its the black plastic thing on the back of your alternator and one of your two connectors plugs directly into it. (if you only have one plug to your alternator then you have overlooked the external regulator)
No part of your charging system is controlled by the computer. There is only one wire that runs inside your cab and it goes to the dash indicator and then splits into two wires, both to your igniton switch. One for the start position, and one for run position.

 

Is it possible that the box on the alternator, like you said, has gone bad? I talked to a mechanic friend a few minutes ago and he said its possible the blower motor is going because that, as of currently, is only drawing down the most power. Could that be possible also?

 

Replace the regulator and find out. The part is about $10-20 and easy to replace - just a few screws once you get the alternator off

 

If removed the alternator to have it tested, it is most likely either the regulator or the brushes - easy to test. There is a bolt on the back which when grounded then bypasses the regulator and the alternator will put out full unregulated voltage if that is the problem.

There is an arrow pointing at it and the words "Ground Here to Test" are molded right into the regulator.

You most likely have the factory 2g (second generation) alternator and they are know for having problems with the bottom connector. In fact they have been known to start trucks on fire.

Fords TSB says you should replace that connector whenever you do anything involving the charging system, including changing the battery.

That connector carries the voltage back to your battery, so a bad connection isn't impossible.

You can buy the regulator by itself if it is the problem and it includes the brushes, which are another possible cause. I just replace the whole alternator, and in this case the plug. Customers don't like it when their alternator goes bad two weeks after you fixed it.

A better solution is to upgrade to a 3g alternator, its far better, higher output and no pesky fires. Will cost more though, at least short term.

One way or the other make sure your battery is fully charged before starting the truck after fixing the charging system. Very hard on an alternator to have to charge a dead battery. The place I have rebuild my alternators recommends a new battery when you replace an alternator.

Oh, your blower motor may be going bad, but wouldn't affect the voltage put out by a good alternator, not to the degree you are experiencing anyway.

 

Awesome thanks for the input gentlemen, I will look at replacing the alternator this weekend and then ill post back and let you know the results.