overcharging

[mulisha00]

98 d1. I was wheeling about a month ago and the battery light came on. I noticed the smaller bolt on the back of the alt was loose and tightened it up but light remained on. Battery was dead so I had it towed home.

Replaced the alt with a used reman alt from a autozone or something. The light was off so I figured everything was good to go. 100 miles later I can smell eggs ect and open the hood only to find the damn caps blown off the battery and everything around it is fucked from the acid. I got a new battery today and installed it and checked the voltage running it's showing 17 volts.

I shut it down and removed what I thought was the regulator from the old alt and put it on the new. The black plastic part with the brushes in it. Installed that and I'm still charging at 17 volts.

So my question is this. Where is the voltage regulator on the alt?
Is the voltage in any way controlled by anything else than the alt? ie the ecu ect.

I need to get this piece of shit going so I can move my damn trailer to throw fucking shingles in again tomorrow when it hits 100 again. Sorry for the rant I'm just tired of shit fucking up all around me and spending every free chance I have on a fucking roof baking.

 

[jafir]

Here a photo of the regulator.

https://bputah.com/Disco Parts/Land_Range_Rover_Discovery_Alternator_Voltage_Regulator.html

 

[mulisha00]

Yeah that's what I've replaced. Mine looks more like this.

http://www.ebay.com/itm/12V-MARELLI-VOLTAGE-REGULATOR-LAND-ROVER-MANY-MODELS-/200287258231

That's why I asked if the computer controlled the voltage or is it all done by the alternator. Everything with the pos rebuilt alt charges at 17 volts with both the old and new regulator.

 

[lrover94]

The regulator controls the voltage. It simply absorbs the excessive voltage form the alt and converts into heat. I cannot say as to what the voltage from the regulator on a LR should be, but on what we work on at my shop 12.5 to 14v at 2000 rpms is considered perfect. Which makes me wonder are you testing you at idle and comparing at normal highway engine speeds???

 

[mulisha00]

I'm checking at idle as soon as I crank it up. I've got a scan gauge. I don't want to pop this brand new battery so if it's 17 at idle I just cut it off.

I don't understand why two regulators are doing the same thing. Is there something else that would make the voltage that high?

 

[DarylJ]

I'm checking at idle as soon as I crank it up. I've got a scan gauge.

Well.....that may be OK, but checking your voltage as reported by the ECU would seem to be quite an indirect way of doing so, therefore adding complexity and the possibility of incorrect data.

Just put a multimeter on it and confirm. 100% direct reading, no chance for other things to be in the way and reporting incorrectly.

If it's still charging too high the regulator is most likely problem. Not sure why you'd think the regulator out of a failed alternator is going to be better than the regulator out of another failed alternator. But either way, they have a bench tester at AutoZone that they will put your alternator on for free.

And the POS rebuild used to be under warranty until you took it apart. Make it look like you didn't before you bring it back.

 

[kc disco guy]

I agree your regulator sounds like its bad also have you checked your 100 amp fuse for the alt? we understand you put a pos rebuild in it but with your "rant" you described it sound like your having a Shitty week and got a bad rebuild unit. On the positive side you will be very experienced in changing out a ALT. And I would do it in there parking lot and retest after you change it out. You try to stay hydrated and be proud of yourself for busting your ass at that tough job to provide for yourself. I will look further in my notes and let you know if anything else come to mind.

 

[lrover94]

If you decide to use a multi meter you won't need to read it at the regulator you can read it at the battery.

 

[kc disco guy]

But check your battery in your multimeter to be sure its getting a correct reading.

 

[Chris740]

Are you sure the pulley is the right size.You might be amazed at what can happen should you spin the alternator to fast

 

[mulisha00]

Thanks for the insight so far.

To clear some confusion.

This alt was pulled from a running truck, not purchased from a parts store by me.

I'm not a roofer. Don't want to me. I'm putting a roof on my house around working 50 hours a week.


I'll ask again. Is there anything that controls the voltage output from the alternator other than the regulator in the alt?

I'll check the voltage at the battery with my tester tomorrow evening.

 

[listerdiesel]

The regulator controls the voltage. It simply absorbs the excessive voltage form the alt and converts into heat.

That is NOT correct.

The regulator senses the battery voltage either at its output terminal (most common) or by remote sensing (unusual these days)

The output of the alternator is controlled by the amount of power put into the rotor through the brushes, this controls the magnetic field of the rotor fingers and that in turn regulates how much power comes out of the unit.

The stator windings are 3-phase, with a rectifer, the rotor is a single phase winding.

Technical information here for those interested. The handbook is Lucas-CAV, but what is in there applies to almost all modern alternators.

http://www.stationary-engine.co.uk/CAV-Electrical/AltBatt.htm

or

http://www.oldengine.org/members/diesel/CAV-Electrical/AltBatt.htm

Peter

 

[jafir]

If it senses battery voltage, would a poor ground cause an over charge?

 

[listerdiesel]

If it senses battery voltage, would a poor ground cause an over charge?

Normally, no it wouldn't.

The Bosch alternators are machine-sensed, with just the output and warning light connections, plus the engine ground.

To overcharge in the first instance, it has to have good connections to pass the current, which tends to eliminate the grounds, but it is always worth checking them. If they need cleaning, don't use regular grease, use a petroleum jelly product which has nothing in it to attack the plating on the connections, and is more water-resistant than regular grease.

It is more likely that a diode has failed in the rectifier pack and gone short circuit, feeding raw AC through to the output.

Peter

 

[mulisha00]

Got it fixed today. Ended up putting another alt on and I'm charging at 13.9 volts.

I did check the overcharging alt at the battery and it was 17 volts at idle. Now I get to deal with the shingles... I'm still interested as to why both regulators caused it to charge@17.

 

[DarylJ]

G I'm still interested as to why both regulators caused it to charge@17.

Because a typical regulator failure mode (shorted diode) will do just that.