inconstant charge

[lowrodderchev]

Hey guys so im having loads of fun driving the heck out of my truck but I notice in getting a inconstant charge last night I was,driving home from work and my battery died alternator good everything's tight started her up and my gauge will marked charge for a bit then no charge any suggestions? P.s. Its all new wiring harness

[47 Fasttoys]

Stick a voltmeter on it. You should see in the 13 to 14 volt range in normal operation. You should be able to disconnect the positive post on the battery while idling and the truck should continue to run on just the alternator. If that's all correct it's time for a new battery, as yours will not take or hold a charge. This is assuming you are running a alternator and not a generator and not running a modern electrical system where the charge is controlled by the ECM.
Rob

[lowrodderchev]

I'm running hei, battery's new and alternator my gauge on the dash is jumping from charging to decharging once in a,awhile

[mr48chev]

From experience an HEI isn't tolerant of low voltage. They like full voltage to work right while the old points and condenser rigs seemed to function with what ever voltage they could get.

Ok, I'm no fan of hillbilly troubleshooting like disconnecting the battery cable to see if the alternator is charging. I know Chrysler ran a couple of cars from Detroit or Chicago to somewhere hundreds of miles away in 1959 or 60 with the batteries disconnected to show that the new alternators could put out enough volts and amps to run the rig but it is really not how you want to test an alternator. If someone takes offense so be it but suggest correct and proper test procedures for these guys who may not have a lot of knowledge please. Lets leave the spit and whittle club fixes on the porch with the spit and whittle club.

Lowrodderchev the first thing is testing with a volt meter to see how many volts the alternator is putting out. Right on the money close to perfect is 14.2 volts. Not all alternators put out the full 14.2 at an idle even though the should if the demand is there for the electrical power. They should keep up with demand and charge over 12.5 volts though even with the lights, fan and what not on. The regulator is supposed to call for more output.

I'd be suspicious of the voltage regulator even if the alternator is fairly new. The simple thing may be to pull the alternator off and take it to someone who can test it on their test machine so you know if it is working the way it should or isn't up to par. That way you have eliminated the rest of the truck from what the alternator is doing or isn't doing and if it checks good to go you start troubleshooting the wiring in the truck.

One thing I have had a hard time with is the spade connectors and especially when a female spade connector is used in place of a factory style plug. Add to that factory style plugs that have the latching mechanism broken That little broken tab on the two wire connector going to the alternator's connectors may let the connection jiggle enough that the alternator gets it's signals crossed. That can be on the far end of the wire at the fuse block too. Tight connections are a must.

Check out the alternator to make sure it is working right and check out the wiring connections to make sure you haven't got one in the charging circuit that is loose and go from there.

[starterman99]

As mentioned check with voltmeter and check it about 1500 rpm as at idle if the battery is discharged the amperage output will be high and that makes the voltage read lower. Also check belt tension, as a slipping belt can cause the same symptom you describe. I have seen lots of shinny aluminum pulleys worn out and causing problems on hotrods.

[lowrodderchev]

I'll double check my belt my pulleys are stock. I check the battery it was charging then out the blue drop down in starting to think theres something loose in my alternator its making a winding noise here and there like maybe the internal voltage regulator is going out

[starterman99]

A high pitch whine could be a bad diode, to check for this use your volt meter set on AC volts hook positive lead to positive on back of alternator, ground to case of alternator, any reading above 0.5 volts indicates diode bad.

[Coupeguy2001]

If you have some # 10 wire, put leads on two wires, and hook to one of those ammeters people put under the dash. Place it where it is protected, and insulate it with foam and duct tape. hook one end to the alternator battery lead, and the other one to the wire you just took off the alternator. use bolts and nuts to secure the wires. It doesn't matter which way you hook the ammeter, because it will read either way if it is an under dash one. If it says negative, turn the ammeter around if it bothers you.
Take a volt meter, and put on the alternator battery lead when engine is running.
you should see 13.5 to 14. 8 volts, somewhere in there. If you just started the engine, the amps might be 40-45 amps, then go down to around 15 without air conditioning.
With air conditioning, it might jump up to 55-60 amps, depending on your equipment.
leave the thing running for a few minutes, and watch the ammeter and the voltmeter.
If the alternator is experiencing a problem, your amps will go lower because its not charging, and the voltmeter will start to go down.
The volt meter will go down to battery volts, around 13.0. It will go a lot lower if there is 40-60 amp load on it. turn off what you can.
When the ammeter pops up to charge, the volt meter will indicate higher volts, like before.
If that happens, the problem is the alternator.
If the volts rise a little, but the amps drop a little, the problem is the battery. The alternator is still carrying the load.
Not a perfect way to find a problem, but it works.
Check to see that you have the battery grounded really well to the engine, and another ground strap from the body to the engine.
bad grounds do funny things.
You can go into the truck, and turn everything on, and see what the amp reading is, and check it with the one in the truck.
That would be a sure fire way to see if the alternator is putting out what your demand is if it just keeps increasing the ammeter reading.
The only thing I wouldn't turn on is the wipers. they might scratch your windshield if run dry.

[mr48chev]

I'm with starterman99 in that if you have a whine in the alternator it could mean a bad diode. Especially if the charging is fluctuating strangely and it isn't keeping a charge.

I still suggest pulling it off and taking the alternator to someone who can hook it up on a good test machine and put it though it's paces and you will know good or bad in the alternator. Good means you have another issue in the electrical system. Bad means you either repair or replace the alternator. Knowing for positive that it is good or bad trumps the daylights out of beating your head against the wall for a week trying to figure it out.

[franken]

I think I'd get a good DVM and measure some voltage before yanking parts or replacing them. You can switch the meter to AC Volts and see what it says, which might suggest a shorted diode if high.
A loose connection will make things act crazy as well.
As far as a parts store testing, meh. I took a battery in to swap reading 9V. They suggested it might need a charge. Uh, no. Battery is history. The point is having a tester, knowing how to use it, and understanding the result are not the same.

[lowrodderchev]

So in park its fine but once in driving its acting funny I put my meter on it and its not giving a full charge while in park so I tried a experiment ran a wire from the hot on the alternator directly to the battery and its giving a full charge now so it must be my hot wire that goes to the starter maybe?

[franken]

WTF does "a full charge" mean?
The only meaningful measurements are voltage at this point.

[lowrodderchev]

Would it be ok to run a bypass wire from alternator to battery? I have a tester that tells you if its charging or not I loaned out my tester and need to go retrieve it

[franken]

No idea what that would measure.

[lowrodderchev]

I'm using a speedway motors wiring harness I posted the question on the web page they said to check the alternator to battery wire but the instructions never said anything about that wire so thought should I add it or is it going to be a issue

[AZ59apacheguy]

I had a new alternator go bad within a month. It started squealing and the Amp needle on the gauge started jumping around just like yours. Took it back, got a replacement, installed and it's been fine ever since. If you don't have the proper tools, any of the major auto part stores can check it for you.....

[lowrodderchev]

here's what I came up with, so its getting 13-14 volts at idle, when I have my headlights on and stereo going is when the issue occurs the needle bouncing and around from charge to discharge (8-12 volts). I notice the alternator to battery wire that came on my harness seems a little small and it doesn't go the directly to the battery but into the key.so I ran a heavier gauge wire from the alternator to the starter and it seems fine so far. I did leave the smaller wire that came with the harness attached. crossing my fingers and hoping it solves the problem. on my next day off I'm going to trace the alternator harness wire and figure out if I screwed up and ran it wrong or are the directions screwy thanx guys for all the help

[OrrieG]

The EZ Wirr kit comes with a jumper wire that is used with high output alternators. Will dig out the information and post it.

[lowrodderchev]

you know what OrrieG come to think of it so did mine I do remember seeing that on the instructions. I should be good I hope. I guess i'll find out tonight on my way to cruise night

[OrrieG]

Back home, EZ wire recommends a #10 from the BAT terminal of the alternator to the large terminal at the solenoid (one battery wire connects to) if you are running an 80 amp or larger alternator. Its on page 14 of the instructions.