question about a wire on the alternator
- Thread starter stangbang302
- Start date
MustangLX-5.0
Founding Member
I'm not even so sure anymore. I thought it was just used for turning on the BATT/AMP dash light, but I heard in a few places that it may actually allow the alternator to function. I do have my doubts about that second point because the current needed would have to be very low to NOT light up the bulb. I would also like to know if this wire is a necessity or not. I don't wish to give out false info unknowingly.
Have you tried to isolate the cause of the short, instead of just cutting wires? What seems to be the problem exactly? Can you describe what is going on in a little more detail? You could have some other problem not related to the alt, shorting out and causing excessive current draw or voltage drop. That's usually the case, and not the alt. wiring. Is your alt stock or the 130A 3G?
Have you tried to isolate the cause of the short, instead of just cutting wires? What seems to be the problem exactly? Can you describe what is going on in a little more detail? You could have some other problem not related to the alt, shorting out and causing excessive current draw or voltage drop. That's usually the case, and not the alt. wiring. Is your alt stock or the 130A 3G?
well for a little over a week now i charge the car during the day and at night i take it off, then in the morning the car is completely dead, when i had the car on the charger i was messing with the wires on the starter and relay and when i took the alternator wire off my voltage jumped up about 2-3 volts then i put it back on and it drops back down, this is with the key off.
well now i dont really believe its coming from that alternator wire, i took the wire off the starter relay last night to see if it would die the next day, well sure enough i just got my hopes up for it not to die and its dead in the morning, i do have all good fuses also. i did that check to where you take the negative off the battery and connect a test light to it and touch the negative post and it should light up if you have a short, i read up on that so i gave it a try and no light. 
Do you have a digital multimeter that has a 10A DC Amp position? If so, disconnect the neg off the batt, hook the meter up in series and take an amp reading. Should be less than 1 amp.
If it's more...pull fuses and start to isolate the circuit. If you isolate it, that will narrow down where you should be looking for your short
If it's more...pull fuses and start to isolate the circuit. If you isolate it, that will narrow down where you should be looking for your short
As for that green wire, it is what tells the alt that it needs to be turned on. It is needed.
If the draw is minimal (you did the first current draw test correctly), take your battery in for a bench test.
If the draw is minimal (you did the first current draw test correctly), take your battery in for a bench test.
So you are drawing 3 and a half amps with the car off (ignore the -...that's just cuz you had the leads backwards) ? Something is shorting out then. You should have less than 1A of current draw with the car off
Leave the meter hooked up and start pulling fuses out and see if you can isolate where that 3.5A draw is. Then post up the circuit and we can start looking at wiring diagrams.
First thing i'd prob do is unplug the fuel pump relay and see if that gets rid of the excess draw
Leave the meter hooked up and start pulling fuses out and see if you can isolate where that 3.5A draw is. Then post up the circuit and we can start looking at wiring diagrams.
First thing i'd prob do is unplug the fuel pump relay and see if that gets rid of the excess draw
MustangLX-5.0
Founding Member
Fuel pump relay contacts sticking. That's my guess. Could also be the ignition switch. Do any of your gauges or dash lights go on while the key is off?
@Hissin, I thought that wire might've been important, I just wasn't sure. Thanks for clearing that up.
@Hissin, I thought that wire might've been important, I just wasn't sure. Thanks for clearing that up.
alright so i did fix the fuel pump problem, that relay next to the computer was filled with water, it rains to much here in georgia and my windshield hasnt been installed just yet, so i dried the relay and then tried it and it worked. thanks for helpin me on finding this short, ill go do the fuse check with the multimeter now and let you know
k did the fuse thing all are good, so i went over to the starter relay, i took the alternator wire off and it dropped instantly to 0.000 then i put it back on and it went to 3.000. now what? im thinking that green wire is telling the alternator to stay on while the car is off, does that sound like it could do that?
k did the fuse thing all are good, so i went over to the starter relay, i took the alternator wire off and it dropped instantly to 0.000 then i put it back on and it went to 3.000. now what? im thinking that green wire is telling the alternator to stay on while the car is off, does that sound like it could do that?
Put a meter on the green wire and see what it reads Key off. It should be zero Volts.
When they bench tested your alt in the store, did they test the diodes? Or did you just have a dynamic test done in the parking lot? If the latter, you'll want to have the alt bench tested in the store.
alright everything is fixed as far as i know, car will start without getting charged the voltage gauge is reading more correctly now, what autozone couldnt do is tell me the voltage regulator in the alternator is bad, all they said is the alternator passed, so i changed out the alternator with another one in the shop and its all good now, thanks for all the help tho hisson50 and mustang5l5
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