Intermittent Electrical Overcharging

[bwilliard19]

Looking for some help/advice with my 2003.5 msp. I recently replaced the alternator and battery on the car. The alternator that I put on had a bad voltage regulator and caused the battery to leak and throw the cel/battery light. I replaced the alternator with another one and that issue went away. But now anytime I open the throttle up all the way the battery light comes on 4k rpm and above. I've gone through the wiring on the car and replaced/fixed the negative battery cable and all the grounds in the engine bay.

I'm down to the point where its looking like the ECU could be the issue but I'm trying not to replace it since it has already been tuned by a tuner and don't want to start that process over again. If anyone has any information or ideas on what I can do it would be really appreciated.

 

[TheMAN]

dud alternator... aftermarket reman junk from parts stores that are bad out of box aren't unheard of

you want it done right, get your original rebuilt by a good local shop, or buy denso reman

 

[bwilliard19]

dud alternator... aftermarket reman junk from parts stores that are bad out of box aren't unheard of

you want it done right, get your original rebuilt by a good local shop, or buy denso reman

The second alternator is a brand new non reman. What are the chances that I got a second bad alternator? I'm puzzled as to why it's only trying to overcharge at higher rpm.

 

[bwalt]

+1 on the aftermarket alternators being no good out of the box, even the so called 'new' units. Denso reman probably your best bet.

Is your belt tight enough? Could be slipping at higher rpm. Alternator charging control is through the ecu if I remember correctly.

 

[bwilliard19]

+1 on the aftermarket alternators being no good out of the box, even the so called 'new' units. Denso reman probably your best bet.

Is your belt tight enough? Could be slipping at higher rpm. Alternator charging control is through the ecu if I remember correctly.

I will look into the Denso, the alternator charging control is through the ecu. If the belt was slipping wouldn't that make a audible noise that could be heard?

 

[bwalt]

Usually a squeal is heard when the belt slips but I'm some cases it won't. It's easy to verify belt tension with the engine not running.

 

[bwilliard19]

Usually a squeal is heard when the belt slips but I'm some cases it won't. It's easy to verify belt tension with the engine not running.

I thought I set the belt pretty tight when I installed it. Do you have a recommendation for how tight it should be?

 

[bwalt]

Just tug on the center of the belt between the water pump and alternator, it should have a little slack and you should be able to twist the belt with your fingers about 90 degrees. Too tight and you'll put excessive strain alternator bearing, water pump bearing and especially the crankshaft main bearings.

 

[TheMAN]

The second alternator is a brand new non reman. What are the chances that I got a second bad alternator? I'm puzzled as to why it's only trying to overcharge at higher rpm.

the regulator is still in the alternator, while the ECU controls what it needs to do... bad bad 3rd world made components are very common these days with aftermarket makers, and sometimes even OEMs... so a dud isn't unheard of

but what did the voltage read at those higher RPMs? sometimes a weak or bad diode can also cause the "battery" light to come on... regardless, that's still a bad component in the alternator

 

[bwilliard19]

the regulator is still in the alternator, while the ECU controls what it needs to do... bad bad 3rd world made components are very common these days with aftermarket makers, and sometimes even OEMs... so a dud isn't unheard of

but what did the voltage read at those higher RPMs? sometimes a weak or bad diode can also cause the "battery" light to come on... regardless, that's still a bad component in the alternator

Well before I fixed the wire damage it was popping up to 18v. I haven't had the time to check the voltage after the wire repair due to my work schedule. Its not showing signs of overcharging like the battery leaking ect. after the wire repair. And no cel now, just the battery light popping on and off at high rpm while driving.

 

[TheMAN]

So, there was wiring damage! You didn't say before

but anyway, it's also possible there's ECU damage from this, but it's also possible a dud alternator is causing the funkiness... I recently talked to a guy in Canada who has gone through 3 ECUs because of 1 dud alternator that fried them

 

[bwilliard19]

So, there was wiring damage! You didn't say before

but anyway, it's also possible there's ECU damage from this, but it's also possible a dud alternator is causing the funkiness... I recently talked to a guy in Canada who has gone through 3 ECUs because of 1 dud alternator that fried them

The wire that was damaged goes to the oil pressure switch. Got a little hot on the original overvoltage from the reman alternator.

 

[bwilliard19]

The wire that was damaged goes to the oil pressure switch. Got a little hot on the original overvoltage from the reman alternator.

At least I think that's what it went to. Its the LG/R wire on the fuse box connector. I've had a hard time tracking down where it goes without removing the entire bundle.

 

[TheMAN]

You'll know where it goes if you read the manual (the wiring diagrams) lol

 

[bwilliard19]

You'll know where it goes if you read the manual (the wiring diagrams) lol

I'm well aware, working on getting the diagrams.