DIY saved me $350 on alternator Repair

[Jeff in MN]

Greetings from the semi frozen tundra.
Yesterday morning I started my 535is (M30) and noticed the dash lights for alternator and brake were glowing dimly. Battery was quickly discharging and the engine soon died and would not even come close to restarting. Later that evening I pulled the voltage regulator to see if it "looked" ok. Seemed fine, and as I was getting ready to put it back in I got the idea to look into the back of the alternator with a mirror. Hmmmmm. One of the contact rings was nice and shiney, the other was brown and rustly looking. Next step, pull alternator. Closer examination on the work bench confirmed that this "rust" could easily be causing a problem. Went to the kitchen and got Q-tips and CLR cleaner. Thru the opening I swabbed the ring while spinning the shaft, then I apply a little more CLR to the tip of a rag and pressed firmly with index finger as I rotated the shaft some more. After a few minutes the connection ring was shiney again. I reinstalled the regulator, reinstalled the alternator and fired her up. JACKPOT!!! no more alternator light and she was charging at a steady 14 volts.

Hope this helps somebody sometime as I could see that it would be very easy for a repair shop to tell you your Alternator is "shot", especially on a high milage car, sell you a new bosch for $250 and charge $100 to install it.

Keep in mind, that you would probably not need to remove the alternator to clean the contact rings, but you would need to loosen the belt to spin the shaft.
Sorry, no pics.

[Dash01]

I rebuilt my alternator completely for not much dough: New diodes were $30, v. regulator ~$14, and bearings about ~$6.

BTW, the local car parts joints wanted about $35 for the bearings, but a local farm implement (Case) dealer had the exact same bearings for ~$6.

I put the alternator in the deep freeze overnight before dis-assembly of the press fitted bearings. Penetrating oil and a small hammer with large socket worked to refit the bearings.

A local machine shop turned the surfaces of the shaft for ~$10.

Works fine for the past several years.

BTW, Costco has batteries that fit the E34, with 100 month warranty, for cheap.

[Jeff in MN]

I rebuilt my alternator completely for not much dough: New diodes were $30, v. regulator ~$14, and bearings about ~$6.

BTW, the local car parts joints wanted about $35 for the bearings, but a local farm implement (Case) dealer had the exact same bearings for ~$6.

I put the alternator in the deep freeze overnight before dis-assembly of the press fitted bearings. Penetrating oil and a small hammer with large socket worked to refit the bearings.

A local machine shop turned the surfaces of the shaft for ~$10.

Works fine for the past several years.

BTW, Costco has batteries that fit the E34, with 100 month warranty, for cheap.

Jeff

[ryan roopnarine]

i find that if the shop believes that you know what you are doing/could do it yourself instead, they will usually do what dash describes (if you provide the parts like the regulator or diodes) ie, press in/out, machine work, clean for $40 or $50, and save you the hassle of freezing, disassembly, playing with presses, and driving around and finding a machinist/machine shop with nothing else to do. found at least two shops in two cities that quoted this price.

and $250? maybe for a rebuilt from autozone! in 2004, a new 140a bosch unit, like the one in my car was already over $300.

[choccibicci]

Had to take the alternator out of my 540 recently, good job too, as upon removing the vr housing, hundreds of fried bugs, waps, and flies fell out!

Quick clean later and all is fine again

[billy]

theres a reason why the rings are rusty!

the carbon brushes arent pushing on it for 1 reason or another, probably worn down and the spring is at full stretch

i would hazard a guess that your fix wont last long

Its madness not to change the brushes/regulator when you have the alternator out, cost is next to nothing.

billy

Greetings from the semi frozen tundra.
Yesterday morning I started my 535is (M30) and noticed the dash lights for alternator and brake were glowing dimly. Battery was quickly discharging and the engine soon died and would not even come close to restarting. Later that evening I pulled the voltage regulator to see if it "looked" ok. Seemed fine, and as I was getting ready to put it back in I got the idea to look into the back of the alternator with a mirror. Hmmmmm. One of the contact rings was nice and shiney, the other was brown and rustly looking. Next step, pull alternator. Closer examination on the work bench confirmed that this "rust" could easily be causing a problem. Went to the kitchen and got Q-tips and CLR cleaner. Thru the opening I swabbed the ring while spinning the shaft, then I apply a little more CLR to the tip of a rag and pressed firmly with index finger as I rotated the shaft some more. After a few minutes the connection ring was shiney again. I reinstalled the regulator, reinstalled the alternator and fired her up. JACKPOT!!! no more alternator light and she was charging at a steady 14 volts.

Hope this helps somebody sometime as I could see that it would be very easy for a repair shop to tell you your Alternator is "shot", especially on a high milage car, sell you a new bosch for $250 and charge $100 to install it.

Keep in mind, that you would probably not need to remove the alternator to clean the contact rings, but you would need to loosen the belt to spin the shaft.
Sorry, no pics.

[Dash01]

Its madness not to change the brushes/regulator when you have the alternator out, cost is next to nothing.

Aftermarket voltage regulators run about ~$12-14 including the brushes.

Or, from a hardware store just buy the brushes @~$2 and install them with a bit of soldering. You can amortize this extravagance over the next ~100 to 150K miles, so it's not as expensive as it might seem.

[Jeff in MN]

theres a reason why the rings are rusty!

the carbon brushes arent pushing on it for 1 reason or another, probably worn down and the spring is at full stretch

i would hazard a guess that your fix wont last long

Its madness not to change the brushes/regulator when you have the alternator out, cost is next to nothing.

billy

for about 2 weeks (not driven) in some pretty damp weather. Regulator and brushes were new last year. Thanks for checking.

Jeff