'82 F-150 charging problem

[Mr. Rivera]

I canged out Starter sol, Voltage reg, New battery cable wires, New(not rebuilt) Starter and alternator, and even purchased a Oprtima Red-Top battery. When you turn the headlights on and put a multimeter to check voltage output, the voltage continues to drop. All the old parts that I changed out were all original. This truck has been good to me until this problem of the charging system has occured. Any thing else I let out that I need to check or chang out?!

[unclebubbles]

Make sure that you have good , clean grounds everywhere. Run some more grounds if you have too to be sure that you have a good ground from: Batt to engine, frame, and body. Run seperate grounds to the alt and reg to be sure thay are well grounded. Sometimes paint, grease, and rust can keep them from getting a good ground. You cant rely on just the fact that the alt is mounted to the block which is grounded, and the case of most external regulators needs to be grounded too. Also check to be sure that you have 12v at the batt term on the rear of the alt. That wire , i believe has a fusible link in it. Make sure your belt is good and tight. From your description, id bet on a bad ground, assuming all these new components test good.

[Selectron]

Good advice there from unclebubbles. If you still have problems after making those checks, could you give us some voltage readings so we can get a clearer idea of what is happening. I'd be interested in three voltage readings:

1. Battery voltage with engine idling - should be thirteen-point-something volts, maybe as high as 14V and it tells us that the battery is receiving at least some charging current from the alternator.

2. Battery voltage with engine revved slightly (should climb to around 14.2V and then hold steady regardless of further increase in engine speed - this tells us that the voltage regulator is working.

3. Battery voltage after being parked overnight, but before starting engine.

That last test would normally indicate whether or not you have excessive current drain when vehicle is parked - you should expect to see around 12.6V although that assumes that the battery was in a good state of charge when the car was parked the previous night, which in your case it may not be.

That does raise the question though - are you sure that this is in fact a charging problem - could it instead be an excessive current drain which is flattening the battery when parked?

Oh yes, and when taking the voltage readings, it's important to probe directly onto the lead terminal posts of the battery - not onto the connectors. The reason being that if you had a poor (high-resistance) connection between connector and terminal post, it would be hidden by taking readings on the connector, but would be apparent when taking readings directly onto the battery post, so that's a good habit to get into anyway.

[FNA]

"When you turn the headlights on and put a multimeter to check voltage output, the voltage continues to drop."

I'd like to ask what voltage you are showing headlights off and on and what exactly you mean by "voltage continues to drop".

Thanx.

[Mr. Rivera]

The voltage reading from the battery(w/multimeter) is 11.50 volts. When the headlight are on is dropes to 10.80 volts, and continues to fall. I disconnected the wires @ rear of alt. and had a 11.75 volt reading. I thought that the new alt. was bad and not recharging the system, so I exchanged it for a new one, that didn't fix the problem. The belts are tight and I have new ground wires that I grounded secure. I tried disconnecting the neg. side of battery and the truck died, thats telling me that batterys not geting chargerd....right??? This truck has been in the family since it was drove of the lot brand new. It has never gave us this kind of problem before. Im thinking about getting ride of the truck cause of this problem.

[KimMG]

Have you checked and made sure the black/orange wire connected to the starter relay is securely connected with clean contacts? Make sure all connections in the circuit are clean and secure.

[FNA]

"The voltage reading from the battery(w/multimeter) is 11.50 volts"

That is a bad battery. Absotively. That's a 12 V battery. If it doesn't hold 12V, it is no good.

A saying I learned in the trade many years ago, "New doean't mean good."

[travis_1021016]

im having same problem. I turn on head lights and first noticed after a few minutes idleing, my interior lights would begin to dim, then eventually the engine would die and battery will be dead. so i tested at battery when lights were on and the voltages continuosly drops. tried driving it without head lights, and eventually would do the same just from useing brakes, (brake lights im guessing.) when the voltage regulator went out a couple months ago, the lights had nothing to do with it. it would run fine with lights on and a charged battery, but wouldnt stay charged. ( so not thinking its the regulator)

[Torch]

Try removing the battery from the truck and stick it on a charger all night long, the following day (with a different car) drive the battery somewhere and have it load tested, that will tell you if the battery is bad or not.

[FNA]

Travis, it sure sounds to me like you are not charging. This could be as simple as a loose belt (or not).

A fault in a charging system does not exclude the possibilty of a bad battery, but your first look should be to the charging system; repair that first.

[praisethelowered]

While you may have a problem with your battery, there is definately something wrong with your charging system. System output should be well over 13 volts. Check for voltage at the rear of the alternator (connection to battery). I'm guessing that there will be no reading. You can then check the resistance of that wire (with no voltage across it) to determine if there is an open in the wire. Also check the leads going to the alternator that excite the field. If they show no voltage, that will keep your alternator from working as well. A good service manual should be able to help you troubleshoot the problem.