I originally had a multiple wire alternator and tossed and put on a single wire. I simply put the yellow wire (bat) to the positive side of the starter solenoid. The battery keeps discharging. I had a local shop go thru and they claim that the alternator is only creating 8.4 max volts. So could it be bad?

Is there a test that I can do that while alternator is in truck? Im charging battery as we speak so after I get responses I will have at least a fully charged battery....Right now I charge....get about 5-6 starts then battery drops to 11volts....then wont kick over. Ive taken battery in a few times and they say is still good.

I have another question on electrical and A/c hook up...may be related...but will post on another thread...

thanks in advance!

 

Get it started. While it's running you should have around 14 volts on the battery. If you have 12v or less, then it's not charging.

 

Though it is not recomended on new vehicals, you can on older ones just start your truck then disconnect the negative terminal on your battery if the truck shuts off then your alternater and or wiring is not doing its job. The reason for this is that an alternator produces more power then your truck needs to run the battery is just there for starting the truck and moral support like when you gun your engine and it needs the reserve power. Or if you get really board just take the alternator off and take it to pretty much any parts store almost all your parts stores can test the alternator for you. for free.

 

oh, I feel stupid....I took alternator out and took to Napa auto parts...While he was looking up something, I looked at back of alternator....totaly fried...I vaguely recall i shorted sometime ago...never thought much of it... Its either that or so close to block that melted wires and shorted....regardless...I think I found the prob....sorry...

 

Lets not do this on any vehicle, old or not. It's just not a good practice and it's best if people get this notion out of their head.

 

If you get the wiring straightened out, and get a new alternator, there is a good chance it still may not charge. There is a fusible link in the large output wire of the alt, and if you had something bad happen in the wiring back there, it may be burnt in two. You can get new ones at the store.

When you get it hooked up, you should have 12 volts on the output wire of the alt with the truck off. If you don't, then the fusible link has burnt out.

 

true but on the old ones it does work, for the shade tree do it homer.

 

ok..... Im still having problems...let me explain what I ve done...

1- I took single wire alternator to have checked. I watched test. At 1200rmps alt put out 12volts...when reved up to 3000rpm put out 14volts

2- With battery unplugged...i charged..went to 13.4volts..then monitored everyday. Its now down to 12.85volts. Then put on truck and hooked up. There is same amount of bleed everyday 0.02volts/day. So I guess I dont have anything thats draining. I imagine that voltage without a load would probably continue to drop til it reaches some level...i imagine about 12!

3- I hooked up battery and alternator. Started truck...now I need some help here. I took lead out of alternator (bat) with 10 gauge wire to positive terminal of starter solenoid ( same side as battery). I started engine and took my tester and put on positive post of starter solenoid and negative wire of testor to negative of solenoid....Is that right? it read 11.4 volts. I tried putting positive of tester to positive of solenoid and to ground but measured zero.

4- I measure voltage of battery after above and voltage of battery dropped to 12.5 volts.. Which is about right....I can drive around and even on longer trip it will eventually not start after about 4-6 starts

5- I cant find a fusible link in wire from alternator to starter solenoid. In fact I replaced wiring just in case..

6- so do i have this wired wrong? single wire from alt to + of starter solenoid...thats it.. right? HELP!!! this is driving me crazy

 

NOT on engines with ALTERNATORS

It will destroy the circuitry in the alternators (diodes,etc)

The practice was called exciting the generator.

Generators were discontinued in 1964

So no vehicles with alternators should have this done to them.

Topic:

Batteries can develop shorts inside themselves or sulfate.

The result is batteries that won;t hold a charge.

The Battery in a car/truck is like the Human heart.. if it ain't good..there's a problem

Take that battery in for testing at a shop.

 

i did take. They not only tested current voltage but if would hold charge. They said was fine. Actually I took in to 2 different places

 

12.5 volts is not right. Get it running again, and put the + of the tester on the bat + solenoid connection,(the large terminal going to the bat +, which is where you have the alt lead correct?) and put the negative of the tester on the neg of the battery. You should get something like 14 volts, 13.8-14.5v.

If you do not, then rev the engine and let it idle back down. These one wire wonder alternators sometimes won't charge until the engine is revved up.

 

ok did what you said.....Im getting anywhere from 13.4 to 14+ now.....So I guess what I will do is take out for a trip and then measure voltage of bat when finished... or at least see after several trips if voltage is at least 12. One other question....im going to rewire truck (its a f100 56) but right now I have an ammeter hooked up...not working right. Whats the proper way for it to measure if its charging or not? or do I really need that at this point? I bought a classic instrument package and it has a voltmeter instead.

thanks for your help!

 

It depends on what type of ammeter it is. Is it the stock 56 type(may have a loop in the back) or is it a aftermarket type that comes with the trio guages?

As long as you are running around 14 volts, you will be ok. It will run in that range all the time the engine is running. If you find the battery is still going dead, you might have a drain somewhere, which will be a different problem to find.

 

its the aftermarket type with 3 gauges. Its measuring negative amps while truck is running.

I really appreciate the help!

 

If it's actually working, only backwards, just swap the wires in the back of the gauge.