225 Alternator

I am trying to figure out if my alternator is doing all it should. I put a voltmeter on the battery and it shows 12.6 volts after sitting a week or so. I start the motor and it stays the same. I turn on the lights with the motor running and it stays at 11.9 for several minutes. seems to me if the altenator wasn't charging the battery voltage would fall. Am I right? Is there a better way to test it? It is a 3 wire (I think it is called). I'm a good mechanic but not a very good electrician.
WHERE's the SPELLCHECK on this thing??

 

ok, when the jeep is running, it runs off the alternator. the alternator not only runs the jeep, but has to charge the battery at the same time, so it puts out alot more than the jeep uses. start the jeep, and pull off the positive battery terminal. if it still runs, your alternator is putting out. if it dies, then it isnt. now, even though its putting out, it might not be enough. take it off and take it to napa or autozone and have them check it. but a quick reference is to pull of the terminal and see if it runs.

 

Thanks, that is great info.

 

I'd say your alternator is bad. When the alternator is running you should have at least 13.5 and max around 15.5. Could be a regulator on the Alternator. What type of alternator is it? I would bypass the regulator for a sec to see if it will put out 15+ volts but I am not sure how to tell you how to do that since i don't know the alternator style. He did mention a good way to check the alternator by unplugging the cable. Just do not do that on any cars with computers cuz it can fry the computer. Another test you could do is a voltage drop on the circuit and check the wiring. Put one lead of the volt meter on the B+ terminal on the alternator and the other on the postive terminal on the battery and have the engine at 1500 rpm with the lights on. You should not get a reading of .2 volts or more. If so your wiring is bad. That tested the positive side of the circuit. To test the negative side of the circuit go from the case of the alternator to the ground terminal on the battery. I'd say its a bad diodes, bad wiring, or a bad regulator. I have more testing information.

A good way to test the battery is to do the following.
Turn head lights on for 15 seconds to remove surface charge on battery.
Check voltage at the battery. If the voltage is below 12.3 (65% charged) charge it till it reaches 12.3. Once it reaches 12.3 or above it is ok to test.
Remove coil wire
Hook up volt meter to battery
Crank engine for 15 seconds while watching volt meter. If it goes below 9.6 volts I would say there is a problem with your battery.

If you have any questions feel free to ask. I am a graduate assistant teaching Automotive electrical here at the local university.

 

Thanks, I tried the disconnect the cable method and the motor died. I'm thinking I should have some continuity between the alternator and POS at the battery and I don't. There is a grnd on the alternator. a terminal coming out the back that is connected to the red wire that plugs into the twin spade connector. The blk wire disappears into a wire loom. Where should the blk wire come out under the dash? Is the red wire correct? I said I was dumb on wiring.

 

Gregg
read thru some of these posts
see if something helps
could be the way your alt is wired
http://earlycj5.com/forums/showthread.php?t=23480&highlight=delco+alternator

 

The link to the wiring diagram is bad. That is what I need to see. Anybody have a good link or just a diagram.?
I am not using the idiot light and have an in dash volt meter. It would seem I have 10 SI and it is for sure wired wrong. HELP!

 

okay
refresh my memory
3 wire, internal reg Delco ?

 

Heck I am just looking at the pictures on the postings Jim and thinking, yes mine looks like that!! I have a wiring kit to rewire the whole thing next winter but I'm trying to have fun with it for the next 6 months. From what I just read (pictures) there should be 2 wires coming from the alternator. The post connects to one spade connector. Then one wire goes from that wire to somewhere and another wire goes from the other spade to somewhere. On mine I don't have a wire going from the post wire (might that be the idiot light wire?) and I need to know where the other spade connector wire goes. Clear as MUD huh!

 

What the Alt shop told me when I changed my external reg to a 30si:

the large post on the Alt goes to the hot post on the starter.
the two wire connector has both wires going to the key, 1 of them (can be either black or red, doesn't matter) passes to the idiot light on the dash, then continues on to the key.

 

do you have a jumper wire from #2 to the threaded battery post lug ?
you need this to 'excite" the alternator
on the rear of the alt, the terminals should be numbered 1 and 2

 

from the Painless manual

 

I just put a voltage meter on the thing to check it here and there. It is producing ZERO voltage. The only voltage is coming into it from the battery. So it is off to the parts store tomorrow for a new alternator.
Thanks for the pointers, be back tomorrow.

 

I ran line 2 to the idiot light (it tells the alt to charge), then the wire goes to the key as well.

 

By threaded BAT post you mean the one on the ALT right? Yes, that is connected. The other wire goes to the BAT through the key.
No voltage is coming out of the ALT...diagnosis is: DRUM ROLL PLEASE....dead alternator. Off it comes and off to my favorite Carquest in the AM.
I think the missing wire would go to the non existant idiot light, which if I had one I would have known the ALT wasn't ALTing. Just got this beast up and running after rebuilding most all of the drive train. Motor, four speed Ford toploader trans, transfer case, and overdrive. Along with a lot of other stuff. Now I'm messing with the little stuff.
Jim when are we going to have a M&G for us locals?? It is almost spring (I Hope!)

 

need the light to excite the alt. try soldering wires to a bare bulb and see if it charges.

 

Hmmm, you mean the wire that connects the post and spade connector needs voltage to it?

 

I sure could use a wiring diagram. But I think I need to establish that the ALT is or isn't ALTing. FLAPS should be able to test it in the AM and tell me if it works and what output I have. There are BIG driving lights for playing out here in the desert at night, it would not be good to have a dead battery in the dark.

 

the #1 & 2 wires; #2 needs the bulb. the post doesn't need a bulb, and shouldn't connect with either #1 or 2.

 

The two spade connectors marked 1 and 2 on the alternator case get wired as follows:

1) goes to ignition switch. a warning light can (not mandatory) be wired in between the ignition switch and alternator. if the warning light is not used a diode (lets power flow only 1 way) MUST be wired in to prevent feedback which would keep the engine running when you turn the key off (the warning light prevents this feedback in the absense of a diode). i use both a diode and warning light, but one or the other MUST be used.

2) this is the remote voltage sensing terminal. it senses voltage and tells the alternator how much voltage to output to keep the system at about 14.2 volts at all times. many people incorectly wire this terminal with a jumper wire to the large BAT lug on the rear of the alternator. This is will sense voltage at the battery. BUT, it is best to sense voltage downstream at a terminal block (GM uses the horn relay) where the largest voltage drop occurs. this way the alternator puts out enough power to maintain 14.2 volts for the entire system, not just at the battery.

The large lug at the rear of the alternator marked BAT gets wired directly to the battery (obviously) using about an 8 gauge wire.