90 535i voltage regulator/ alternator question - solved

**Neel** · 10-08-2018, 09:44 AM

As said in the title - I have a 1990 535i

I replaced my alternator with a rebuilt spare about a year ago, it is now showing around 11v when doing obc test #9. Which means its time to think about rebuilding the one that i pulled out of the car.

Question 1
The unit that I initially pulled out of my car is a Bosch AL143x (115amp output) the brushes on the Voltage regulator are probably around 40% long so they're on their way out, so that is the first thing I will be changing. My question is the following, what is the proper voltage regulator I should replace it with? Brand aside I am getting confused by the different output amp voltage regulators, I see some that say 80, some that say only for certain models ?

Question 2.
The Alternator that I shoved in my car was a unit I had rebuilt at a local shop, I just didnt/dont have time to do it myself. Seeing that the 535 was available with 2 different voltage alternators I'm wondering if the one in the car is the wrong one ? I've seen 140amp and 115amp even seen some 90amp alternators available for the car. Would I see any crazy issues if the one in the car is a 90amp unit ?

Thanks in Advance.

**demetk** · 10-08-2018, 01:17 PM

I use the Hella regulator with good results, https://www.rmeuropean.com/Products/...022-MFG44.aspx

Pretty sure any alternator will work but I would go for either the 115 or 140 amp units.

**Neel** · 10-08-2018, 01:56 PM

Thank you for the quick reply. Ordered 2 of them and 2 fuse-able links from them

. One of these days we're going to have to meet up.

**zubbie** · 10-09-2018, 07:13 AM

When I replaced my 535 alternator the 140 amp version as cheaper, although I had to use the 735 part number to order it.

**shogun** · 10-09-2018, 08:53 AM

M30 and M70 have the same voltage regulator (no matter how many Amps), as long as it is a Bosch alternator. That voltage regulator is for a slip ring of 28mm dia. The M60 engine with Bosch alternator has the compact alternator and there the slipring is 14/16mm = voltage regulator is different.

**Neel** · 10-18-2018, 09:01 PM

Popped in the new voltage regulator at work. The brush on the front or inner most brush on the regulator when it is in the alternator was worn down shorter than the other one. I didnt check my work and overlapped the PS belt and it snapped the Power steering belt after causing quite a ruckus. So that sucks and i had to re-install the belt sans the PS belt BUT, when i did the diag test on the obc it was showing only 12v at idle. The tension on the Alt belt is good.

Is there anything besides an alternator related issue that could cause that ? I did use a kind of jenky wire as the signal wire (possibly 12-14ga wire), there also seems to be some corrosion on the starter where the signal wire attaches to, nothing heavy but it the nuts are starting to show signs of rust.

Would a fusible link on its way out have something to do with this ? I am not experiencing any issues with any of the interior controls be it window switch operation or wiper operation, so I've ruled it out. Its starting to get really frustrating at this point.

Oh well, time to get all new belts now...

Thanks !

**shogun** · 10-18-2018, 10:08 PM

When 1 brush of the regulator was worn down shorter than the other, then probably it is time to change the slip ring, because that has too deep groves, example
http://info.europartshouse.com/tech-...g-replacement/
https://www.audizine.com/forum/showt...new-slip-rings

**alang1990** · 10-19-2018, 10:41 AM

Did you ever do the diag test on your obc when there was nothing wrong, like months ago? What voltage did it show ?

Do you have a handheld voltmeter ?

**Neel** · 10-19-2018, 08:17 PM

nope never did the diag test when everything was good, didnt know about it at the time. Voltage at the battery is showing similar to the obc test which is 11 to 12, sometimes a spike to 12.7. A thought I was having was if the exciter wire was damaged then it could cause the alternator to not send power to the battery ? Im not sure, it was just a thought, Im going to have to check the wires, if it turns out to be the case then I just cost myself a belt and a whole bunch of down time.. If its not the regulator it could be something else BUT the alternator was rebuilt several months ago, not even a year.

**shogun** · 10-19-2018, 08:47 PM

Exciter wire: if the battery light goes on with ignition on and then the light goes off when engine has started, exciter wire is o.k.

**alang1990** · 10-19-2018, 09:56 PM

Can you measure current output from the multimeter directly? Connect the a voltmeter to the B+ output and the other lead to body ground or the metal housing of the alternator and run the engine. This will eliminate all intermediate wiring and you will see the direct output of the alternator. If its good even under load then you know its the wiring between the alternator and the battery. If its poor then you know its the alternator alone.

Like Shogun said, its probably a bad slip ring. This is very bad news because its a pain to change out. When your alternator was rebuilt a few months back, was the slip ring changed ? They usually never do that during a rebuild unless its very bad - usually only the bearings and carbon brushes are changed. And if the use harder material for the brushes than stock carbon, the wear on the brushes will be lower, but the wear on the slip ring will be higher.

If you don't have a multimeter and it sounds like you don't have one, please get one. It is an indispensable tool for old car maintenance. And it costs like a few pounds only.

- - - Updated - - -

Originally Posted by Neel

Would a fusible link on its way out have something to do with this ?

Thanks !

I believe Shogun mentioned this recently here, so I would say its a target. They are cheap and easy to replace and will go out anyway, get them for the two links on the car. Temporarily you can bridge them with wires just to test the theory out.

**Neel** · 10-20-2018, 08:52 AM

I have a multi-meter, its a cheap one from harbor freight, the battery light fades in and out when the engine is running, more than likely im leaning towards the exciter wire. I didnt even think to test the B+ post on the alternator, im really kicking myself in the ass for not properly diagnosing.. ugh. going to drive into work and check to verify will update when i can. My car is at work, I've using a car from work to get around lol.

**Neel** · 10-20-2018, 06:14 PM

So i just put a tested good alternator in the car.. tested the +B on the alternator with the car running - it tested at 13.7 at idle. tested the battery, battery tested at 9volt. I have no idea where to look right now.

**shogun** · 10-20-2018, 06:40 PM

Did you already make a load test of the battery? 9V is basically a dead battery. You may have a weak or dead cell in the battery http://www.batteryfaq.org/
http://jgdarden.com/batteryfaq/carfaq4.htm#load

**alang1990** · 10-20-2018, 06:48 PM

Run the engine for awhile or go for a drive. It probably just needs a recharge.

**Neel** · 10-20-2018, 07:04 PM

After putting the alternator in the car i drove 35 miles at varied speeds, as i got closer to home the battery started reading lower and lower on obc test. The battery is brand new. - quite literally, i put a new battery into the car about 2 weeks ago thinking the battery i had was bad, turns out it wasnt the battery bc the same low voltage was being displayed on the obc. As soon as i saw that i stopped driving the car.

**demetk** · 10-20-2018, 07:08 PM

Do you have it connected? There should be 2 black wires on the starter's positive terminal.

**Neel** · 10-20-2018, 07:24 PM

didn't mess with the starter at all, and after putting the alternator on the car and starting it at work, the obc diag was reading at 11.7, i tested the alternator at 13.5, i did not get a chance to test the battery as we have a new procedure to close with alarms and i was there working on my car not in official capacity.

**demetk** · 10-20-2018, 08:46 PM

The reading at the alternator should be the same as the reading at the battery. I think something's not right with your connections and/or battery wires.

**shogun** · 10-20-2018, 08:46 PM

Where is on the E34 battery the ground wire connected to the chassis? On the E32 the wire goes from the battery to the seat support, in front of the seat support passenger/right side rear there is a plastic cover, underneath is another plastic cover bolted, after you remove this, you can see the bolt/nut holding the ground wire. I remember that on E32 some had battery/voltage/electrical problems because the nut on this connection was not tightened, see here where it is on the E32
http://www.ow.no/index.php?option=co...&g2_itemId=132
http://www.ow.no/index.php?option=co...&g2_itemId=136
http://www.ow.no/index.php?option=co...&g2_itemId=140

**alang1990** · 10-20-2018, 08:49 PM

Battery terminals not tight or battery ground point corroded or something.

Battery can be tested by shutting the car down and, checking voltage between the b+ jumper post and body ground in the engine bay.

If the alternator is good (it is) and the battery is new it is working related. Easy fix. Might have been the problem all along. Hope you didn't throw away the old battery.

**Neel** · 10-20-2018, 09:05 PM

the old battery was traded in to interstate as i thought it was a faulty battery, turns out i was given the wrong battery then entire time, the car would intermittently work. When i did test the alt with the volt meter there was a spark when i grounded the neg volt meter terminal.... will check battery ground when its not raining.. I hope that is all it is.

**alang1990** · 10-20-2018, 11:47 PM

Originally Posted by Neel

When i did test the alt with the volt meter there was a spark when i grounded the neg volt meter terminal.

But how can this be ? You must have made some mistake. Maybe you did not select voltage on your multimeter but current or something. In that case the current surge would be capable of ruining it.

While you're checking, bridge the fusible link terminals on both your fusible links like so :

Fusible Link A1.jpeg

..and then check the voltmeter readings both directly on the alternator and through the obc while the engine is running and when throttled up at neutral. Then remove the clips one after the other and recheck values.

I'm assuming of course that you've never had the fusible links changed before.

As shogun said check all the B+ points from the alternator to the battery and also check the battery's ground point. Might as well clean it of corrosion while you're at it with light sandpaper. Disconnect battery's ground before checking the B+ wiring.

**shogun** · 10-21-2018, 03:01 AM

Locations of fusible links E34, pics here https://www.bimmerforums.com/forum/s...=fusible+links

**Neel** · 10-21-2018, 07:50 AM

I've visibly inspected the fusible links, they looked okay (did not see any micro cracks or fissures). I haven't had any issues with the wipers or windows, or any intermittent power loss issues. so i ruled out the fusible links. Zero corrosion on the battery terminals, and on the alt connections.. There is some rust on the fastening hardware on the starter, but it is not green corrosion so i ruled that out. I'm going to let it warm up before i head out to the car as its 30 right now. I will re-check everything because I may have missed something.. Also have a new fusible link i will change out.. the rivet style i dont have so that one ill have to find an audio style fuse block to replace with.