Alternator issues

[Ross]

Just put an alternator from an '87 leone into a project I'm working on.... AFAIK it was a good working alternator.... but when the engine is running the alternator warning light glows dimly and the voltage goes up to 17 or 18V when it's revved. Any ideas -- could this be a wiring problem or is there something wrong with the IC regulator...?

 

The plug on the back of the alternator -- one should go to the dash warning light (that's working, warning light is on when ignition in on position and engine not running, dims when engine starts) and the other should go to +12V when ignnition is in on position -- correct?

 

Cheers all.

[GeneralDisorder]

Internal regulator has failed. Replace the alt. Wireing will not cause those symtoms.

 

GD

[Ross]

Lame..... Cheers for quick reply.

[TRAVIS75]

I spent years repairing and rebuilding starters and alternators for a local company. As a general rule, when the regulator goes bad the alternator quits working completely, it says in your post that it is charging at 17 or 18 volts, when and if it is truly charging this high, it won't cause your battery light to turn on, it only comes on if the alternator is not charging, not because of excessive voltage.

 

The first thing you need to do is check the "actual" voltage if you haven't already. Get a digital or analog volt meter and check the voltage at the battery, as well as the main output wire off the back of the alternator, both voltages should be relatively close, within say .2v. Anything above 14.6 or below 14.0 is nearing the out of normal range.

 

If those voltages are the same, check the voltage leading to your volt meter on the dash, again should be about the same, if its not, then there is a problem with the wiring leading into that part of the harness leading to your in dash volt meter, this is true whether the voltage is reading higher or lower.

 

My guess, and its completely a guess since I'm not familiar with all the wiring on these vehicles, is that your "idiot light" on the dash isn't receiving correct info in regards to whether it is charging, which again points to wiring.

 

The easiest solution before you start chasing wires is to pull it, take it in and have it tested, ya never know it could be in that 1 percent of alternator failures that actually go into "full field" (overcharge) mode before complete failure.

[Speedwagon]

I spent years repairing and rebuilding starters and alternators for a local company. As a general rule, when the regulator goes bad the alternator quits working completely, it says in your post that it is charging at 17 or 18 volts, when and if it is truly charging this high, it won't cause your battery light to turn on, it only comes on if the alternator is not charging, not because of excessive voltage.

 

The first thing you need to do is check the "actual" voltage if you haven't already. Get a digital or analog volt meter and check the voltage at the battery, as well as the main output wire off the back of the alternator, both voltages should be relatively close, within say .2v. Anything above 14.6 or below 14.0 is nearing the out of normal range.

 

If those voltages are the same, check the voltage leading to your volt meter on the dash, again should be about the same, if its not, then there is a problem with the wiring leading into that part of the harness leading to your in dash volt meter, this is true whether the voltage is reading higher or lower.

 

My guess, and its completely a guess since I'm not familiar with all the wiring on these vehicles, is that your "idiot light" on the dash isn't receiving correct info in regards to whether it is charging, which again points to wiring.

 

The easiest solution before you start chasing wires is to pull it, take it in and have it tested, ya never know it could be in that 1 percent of alternator failures that actually go into "full field" (overcharge) mode before complete failure.

 

It is fairly common for these Hitachi alts to die this way. I've had 2 die this way, with them charging up to 17/18 volts. And yes, it does cause all the red lights on the dash to turn on(at least in an EA81).

[zyewdall]

It is fairly common for these Hitachi alts to die this way. I've had 2 die this way, with them charging up to 17/18 volts. And yes, it does cause all the red lights on the dash to turn on(at least in an EA81).

 

I've had one of them die this way too... overcharging. I can't remember if the lights came on, but I remember the voltage gauge was close to pegged, and a DMM agreed that it was overcharging.

[GeneralDisorder]

The light comes on because of AC current from the failed rectifier diodes in the VR - it glows dimly as the AC reverses direction and for a short time durring every sweep if the sine wave the voltage is lower than the battery. The VR is toast and it's not worth fixing on these units. It's a very common failure mode for the VR's in these. They fail to AC current and high voltage. The one in my GF's sedan did this same thing a couple weeks ago and that's probably half a dozen at least I have personally seen do this. I tossed in a Bosch reman I scored at the junk yard for $37 and it was on it's way as if nothing had happened.

 

GD

Edited May 5, 2010 by GeneralDisorder

[Subarule]

My original Subaru alternator did not die all at once. Funky things were going on a for a while. The tach would wander all over the place. That went on for at least a week. Overcharging was showing on the volt gauge. The headlights would dim on their own. The dash lights did the same thing.

 

I wasn't able to get it checked out right away because I was working 12 hour rotating shifts and didn't have a day off or over a week. Then it dies totally on me when I was coming home on one of the biggests interstates in the U.S., at 5 in the morning. Nothing like sitting on a wicked curve at the base of a sheer rock click before dawn in a little Sube, with a zillion semis whizzing by and rocking that poor little car back & forth like a dinghy on a stormy sea. And not a single thing would work, not even the hazard lights.

 

What fun!! That was the day (10 years ago) I decided I should probably get a cell phone.

[ivantruckman]

The light comes on because of AC current from the failed rectifier diodes in the VR - it glows dimly as the AC reverses direction and for a short time durring every sweep if the sine wave the voltage is lower than the battery. The VR is toast and it's not worth fixing on these units. It's a very common failure mode for the VR's in these. They fail to AC current and high voltage. The one in my GF's sedan did this same thing a couple weeks ago and that's probably half a dozen at least I have personally seen do this. I tossed in a Bosch reman I scored at the junk yard for $37 and it was on it's way as if nothing had happened.

 

GD

 

ive had 6 die this way on me, 3 this year... its a subaru thing

[Ross]

I'm pretty confident on the voltage measurements, I'm reading them from my laptop connected to the megasquirt ecu. The dash light comes on if the alternator voltage is significantly below OR ABOVE the battery voltage. In this case it sounds like it's above batt voltage.

[Ross]

OK, so I replaced the VR with one from another identical alternator I had lying around (it doesn't charge at all for some reason....). When I first started it up, the dash light was still glowing dimly. To check if the wiring to the VR was OK, I then hooked a wire directly from the + battery terminal to the sensing terminal of the alternator -- this seemed to fix the problem, as when I started it up again the light did not glow and the voltage stayed around 14V when I revved the engine....

 

I took the extra wire off while the engine was running, and it still seemed to behave correctly. However, next time I started the engine the same issues reoccurred..... voltage increasing with revs and the warning light glowing. Adding the extra wire into the circuit no longer has any effect, it still isn't working right.

 

So now I'm really confused. Either:

--The VR I swapped in was just about to die of natural causes (seems pretty unlikely)

--There is something in the way it's wired that is destroying the VR (possible??)

--There is something in the way it's wired that is preventing the VR from working correctly that is an intermittent fault (the vehicle has been submerged a number of times and there may well be bad earths/connections still lurking about) - but is there any wiring scenario that would cause these symptoms?

--The diodes are bad causing VR failure? But the voltage logs from the megasquirt look fairly smooth.

--Something else is going on.

 

Any thoughts??

[987687]

Could be the diodes. But you're beating a dead horse. Just get a new alt.

[naru]

The diodes are bad.

[Cougar]

Excessive ripple voltage from bad diodes in the alternator was most likely causing the warning lights to glow dimly. Replace the alternator with a known good one. You may want to replace the VR also at the same time. Be sure the battery is in good shape too.

[Ross]

The VR is of the internal IC type. The vehicle has two near new batteries in it so should be fine there.

 

I'll find another alternator, but I am still rather perplexed that this has happened twice in a row now.... seems an odd coincidence, but these things do happen.

 

Cheers.

[Cougar]

Make sure the battery is ok and there isn't a problem with the wire between the battery and the main output terminal on the alternator.

[987687]

The VR is of the internal IC type. The vehicle has two near new batteries in it so should be fine there.

 

I'll find another alternator, but I am still rather perplexed that this has happened twice in a row now.... seems an odd coincidence, but these things do happen.

 

Cheers.

 

Bad diodes will ruin a VR. So if the diodes are bad it isn't surprising at all that you blew two VRs in a row.

[81EA81]

Recently the Brat started to overcharge. I thought it was the gauge so I got my DMM.(best 5 bucks I spent) on the battery and the voltage slowly climbed to 18v then I shut it off.

I assumed the alternator was the issue.

 

Lucky for me I have a spare that came with the car. As I went to install it I was having trouble getting the ears to fit on the bracket. Then I thought could the be different styles of alternators for EA series cars?

 

Do the 80-82 style alternators differ from the rest? no IC Reg.(internal Current?)

 

Here is a pic of the alternator that came off the Brat.

Heres the spare I had troubles getting to fit.

 

 

Alt. off the 81 Wagwam

 

 

All three.

 

So do the early EA81s have an external regulator? Can I run it on the 86?Thankyou

[Cougar]

The 81s do use an external VR. They can't be used on the newer 82 models which have an internal regulator.