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[McClain]

I started this because I really need help, I have tried to read everything out there and on this site to figure out my electrical issues, but a few months ago I put a new alternator in and it ran my car fine for a while but then recently it has been acting really odd. It started with the battery only charging to 12 volts when the car is running and dipping lower when running anything with electrical but then bouncing back when I turned them off, It then continued to do this but then switched to not bouncing back and just killing the battery. However this whole time the battery light has not come on at all even when the car is about to die and in the past, with the old alternator it would come on when the battery was about to die. I went and got the battery tested and it ended up being bad so under warranty I got a new one. It worked great for a few days still only charging to 12 volts and dipping down with lights but bouncing back, now it is just not charging at all, I will jump it or sometimes I won't need to, but then anything electrical that I turn on instantly kills the battery. I have checked all of the wires and it's telling me they have a good connection but now I am all out of options, can anyone please help I am all out of ideas and have no ideas where to go from there. Please help if you can!!!

[McClain]

I should add that the new alternator I put in was a 70-amp Mitsubishi and the one that was in before was the 85-amp bosch so not sure if that could be the problem but I did do some rewiring.

[EShepherd]

I should add that the new alternator I put in was a 70-amp Mitsubishi and the one that was in before was the 85-amp bosch so not sure if that could be the problem but I did do some rewiring.

You say the car is only charging at 12v, can you explain how and where you are taking this measurement?

When you replaced the alternator, did you use a new unit or a remanufactured one? Reman units are known to be pretty hit-or-miss.

What exactly did you do to modify the wiring? I believe the connectors for the two different alternators are different. Your symptoms sounds like what I'd expect if someone got the terminals wrong at the alternator connector.

[McClain]

I should add that the new alternator I put in was a 70-amp Mitsubishi and the one that was in before was the 85-amp bosch so not sure if that could be the problem but I did do some rewiring.

You say the car is only charging at 12v, can you explain how and where you are taking this measurement?

When you replaced the alternator, did you use a new unit or a remanufactured one? Reman units are known to be pretty hit-or-miss.

What exactly did you do to modify the wiring? I believe the connectors for the two different alternators are different. Your symptoms sounds like what I'd expect if someone got the terminals wrong at the alternator connector.

To see that the battery is only charging to 12v I am either using a voltmeter to check it when I’m not driving and the car is idling or I am looking at the voltage gauge. The alt that I got was a remanufacture one, for the wires I got a plug from rock auto where I got the alt and I wired it using the heat shrink and crimping, I put the striped black with the negative side and the striped red with the positive side. Not very good with electrical work but I think that it is a good connection and I have a heat shrink protection over if then electrical tape to protect it.

[EShepherd]

I should add that the new alternator I put in was a 70-amp Mitsubishi and the one that was in before was the 85-amp bosch so not sure if that could be the problem but I did do some rewiring.

You say the car is only charging at 12v, can you explain how and where you are taking this measurement?

When you replaced the alternator, did you use a new unit or a remanufactured one? Reman units are known to be pretty hit-or-miss.

What exactly did you do to modify the wiring? I believe the connectors for the two different alternators are different. Your symptoms sounds like what I'd expect if someone got the terminals wrong at the alternator connector.

To see that the battery is only charging to 12v I am either using a voltmeter to check it when I’m not driving and the car is idling or I am looking at the voltage gauge. The alt that I got was a remanufacture one, for the wires I got a plug from rock auto where I got the alt and I wired it using the heat shrink and crimping, I put the striped black with the negative side and the striped red with the positive side. Not very good with electrical work but I think that it is a good connection and I have a heat shrink protection over if then electrical tape to protect it.

If you are reading 12v at the battery with the vehicle running, then your alternator is doing nothing. It's either bad, or you have it wired wrong. When you wired up the new plug, how did you check which terminal on the alternator was for power and which was for ground?

[McClain]

I should add that the new alternator I put in was a 70-amp Mitsubishi and the one that was in before was the 85-amp bosch so not sure if that could be the problem but I did do some rewiring.

You say the car is only charging at 12v, can you explain how and where you are taking this measurement?

When you replaced the alternator, did you use a new unit or a remanufactured one? Reman units are known to be pretty hit-or-miss.

What exactly did you do to modify the wiring? I believe the connectors for the two different alternators are different. Your symptoms sounds like what I'd expect if someone got the terminals wrong at the alternator connector.

To see that the battery is only charging to 12v I am either using a voltmeter to check it when I’m not driving and the car is idling or I am looking at the voltage gauge. The alt that I got was a remanufacture one, for the wires I got a plug from rock auto where I got the alt and I wired it using the heat shrink and crimping, I put the striped black with the negative side and the striped red with the positive side. Not very good with electrical work but I think that it is a good connection and I have a heat shrink protection over if then electrical tape to protect it.

If you are reading 12v at the battery with the vehicle running, then your alternator is doing nothing. It's either bad, or you have it wired wrong. When you wired up the new plug, how did you check which terminal on the alternator was for power and which was for ground?

When I was doing the rewiring, there were three different wires. There was one that bolted onto the alternator and I left that one bolted it onto the new one then for the distributor plug I used the wiring diagram to see that the black-and-white wire was ground and the red and white wire was the charging one. I went ahead and ordered a new alternator. It’s gonna be the same one, but the other one was under warranty so I can get it for free, hopefully I can see if that will fix the issue. It wouldn’t make sense if the wiring was wired wrong for the car to work for a couple months, and then stopped working, I don’t think that that would be the case but I might be wrong.

[Rocketman]

It sounds like you have a bad alternator. They can partially fail, giving *some* voltage to the battery but not fully charging it.

I would replace the alternator, or at the very least pull it and have it bench tested

[McClain]

It sounds like you have a bad alternator. They can partially fail, giving *some* voltage to the battery but not fully charging it.

I would replace the alternator, or at the very least pull it and have it bench tested

Yup! Having it replaced, it was the last place I wanted to look because I didn’t get it even a year ago but hopefully it will fix the problem! Thanks for your help!! Also didn’t know they could put out partial power that good to know thanks!