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Alternater

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GaryBeu

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So our alternater went TU and is being rebuilt. Can someone give me a SIMPLE explaination of how one works? We have one wire going to the indicater lamp and one hot (12 volt) wire coming into the alternater. What causes 14 or so volts to go back to the battery? Does it somehow reverse itself in that hot wire? Thanks...I'm really ignorant on this one. I tried the internet and youtube videos to no avail.
 
The simple answer is,yes it does,or appears to reverse in there.
But, as the alternator turns,the ign light supplies a small current to the alternator,once the voltage in the alternator goes higher than the battery voltage the alternator then charges the battery through the brown wire.By then the ign light should be extinguished.

Stuart. :cheers:
 
There used to be a site called "How Stuff Works"... see if you can pull anything up there..
 
I have had several rebuilt and never much luck. I hope your rebuild goes well. I have a new Moss unit on my 73B and its working great and when the 74 GT alt. gives up I will be doing the Saturn conversion. Bob
 
Well,here's where we are now...nowhere! Got the rebuilt alternator back today with new brushes, rectifier, and regulator. Put it in and hooked it up. Forgot to disconnect the battery and touched the brown hot wire to both large terminals just long enough to get a small blue spark (did that fry the alternator again?). Turned the key to "on" and got no ignition light. Started the car and, after idling for about five minutes, the light came on. The higher I revved it, the brighter the light got until it burned out! We still have no charging to the battery. What don't I know?? This is driving me nuts. Thanks.

Gary
 
OK Gary, before we do anything else, let's check if it is burnt. I managed to burn mine (don't ask) and actually put a GM alternator on it - partly cause cheaper and partly cause better output, but, while that's another option, let's see what you got. Take off the alternator and take off the top. If you look at the picture I've attached there is a brass bolt head in the lower and right 1/3 quadrant. If you look at it you can see it holds a piece of melted metal in place - that is what you are looking for to be solid and connected (you'll see where it goes.) If that is OK, we'll see what we can find. One thought is that it might have to do with your previous owner's wiring repair that was turning off your headlights. But, one step at a time. And, don't loose heart, we're still close.
 

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Thanks JP. I'll pull the alternator and check it. I'll be back!
 
OK JP...it's fried. Here are a couple of pics...not real clear since I have a cheap camera.

The brass bolt head and yellow wire that your photo shows isn't in my alternator! There is a large hole where that dome-shaped thing is on yours. Hopefully, you can see the burned wire where two of them touch and the inside of the little metal case is melted. Does this make sense to you? Thanks.

Gary

MGBRebuild007.jpg


MGBRebuild006-1.jpg
 
well, sadly, back to the rebuilder, though you might want to contemplate a GMDelco swap https://www.mgexperience.net/article/delco.html (others jump in here)

while I understand that hooking up the alternator without disconnecting the battery was not the smartest thing you did yesterday (at least I hope not :wink: ) still, I'm not clear in my head why current would be flowing to the alternator and not from. Others help me out here.
 
JP...here is a similar photo to yours. Mine seems to be missing what you described plus that round thingy on the right!

Gary

MGBRebuild008-1.jpg
 
My understanding is that the brown wire connected to either one of the large posts is hot...mine is.
 
Also, JP please look at my photo and you'll notice that the small orange wire is hooked to the large terminal in the middle. On yours it is hooked to the small terminal for the light. Could that be at least part of my problem?
 
Gary, I am wayyyy out of my depth on this - but, will take a look at mine after supper and try to make some sense of it all
 
JPSmit said:
Gary, I am wayyyy out of my depth on this - but, will take a look at mine after supper and try to make some sense of it all
Click to expand...

Gary, you might want to check with JP tomorrow...he's going to be in a food coma after his supper tonight.....see the "Birthday Dinner" thread! :laugh:
 
Yeah, back from the dead. I just looked in my Bentley book and it looks like a different alternator. I have a little expertise around fuses and terminals but none around alternators themselves. So, I hope someone else jumps in here. You probably want to take it back to the shop where you had it. I don't know about the orange wire - though I wonder if it might be the regulator only because it seems that a surge of power might indicated that the voltage is unregulated. Either way, sorry I can't be more help.
 
Seems that everyone is as confused as I am since there are no further recommendations! :smile:
 
Gary, I'd start by having a heart to heart with your alternator guy
 
That's on the agenda this morning...
 
Took the alternator back to the repair guy. He agrees that the problem is~probably~that he put that orange wire on the wrong rectifier terminal. He agrees that it should probably go on the small term for the ign light. He'll replace parts, etc. at no charge. Hope it works this time! Anybody else have any input either yes or no?
 
sounds like a plan, let us know
 
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