Ive had three lights going on and off intermittently the last few days. The Battery light, the brake light and the Parking brake light all seem to light up at the same time. Actually the little arrow light beside the empty side of the fuel gauge was also lit up)

The last two days they seemed to be getting dimmer and the headlights were dim too. Today they stayed on for the whole time the car was running (30-40min) and on the second trip home when the ignition was turned off, it wouldn't start again.

We had to get a boost and then it took off once again just to get home. Now its sitting in the driveway unable to start.

I'm suspecting the alternator. I have a good very large newer battery so i doubt its that.

How complicated is it to rebuild an alternator? From the little I read It seems like it may only be replacing the brushes and the regulator? I'm not sure what part the regulator plays or where its located though.

Is there a way to test with a meter how the alternator is performing?
Thanks for any help... I guess I know what Ill be doing for my day off.....

Most likely the voltage regulator. It connects to the rear of the alternator. to screws, and it slides out. new reg comes with the brushes. It is about $35.



Charlie

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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

Harbor Freight sells digital Volt/Ohm meters (millimeters) for $5 or less when they are on sale.
You will need to charge up your Battery so you can get the Engine started and running and set the meter to the proper DC voltage range with the red probe on the + Battery terminal and the black probe on the - battery terminal and read the voltage.

You need to be getting around 13.5 volts for the Battery to charge.

Sounds like you have already looked up some threads and know that slipping belts, loose Alternator Pulleys, worn Brushes, poor Alternator wire connections, poor Battery terminal connections and poor Engine Ground strap connections can all cause the Alternator not to charge.

As far as rebuilding the Alternator goes there is no how-to-do it with pictures that I have come a crossed.
I have had mine apart to the extent that I changed both of the Bearings and it is no more difficult than the Delcos I have had apart with the exception that I needed a Bearing Plate and a Gear puller to pull off the front Shaft Bearing on mine.

I do not know if you if that was the only way to get the Bearing off because since I already had those Tools I used them.
A few members have replaced bad Diodes in there Alternator but I have never done that so cannot comment on that.
At least one member has changed the Slip Ring.

Most have limited their Alternator repair to replacing the Brushes, Voltage Regulator or bearings.

Another way to go would be to Charge the Battery; get the Engine started and drive to the nearest Auto Parts Seller that will test your Charging System for free. They will Tell you if it is charging or not.

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84 300D, 82 Volvo 244Gl Diesel

Hi there, thanks for the tips. So just wondering, When I do a voltage test with the meter, I would be placing the probes on the battery terminals?

Wouldnt that simply give me a reading of what the battery is putting out and perhaps a mix of what may be coming out of the alternator?

My thought would have been that I would have to disconnect the battery and test the alternator separately. But I guess the car would stop running though if the alternator wasnt working..or would it?

It'll "Blow Out" the Diodes, instantaneously.

Testing with the engine running at the Battery Terminals (Alternator connected)
Gives you the Alternator Output.

Rebuild Bosch 120 Amp Alternator (Pictorial)(Almost ALL Bosch alts are similar):

http://www.oichan.org/mods/alter/alter2.htm

Rebuild Bosch 143/150 Amp Alternator(Pictorial):
(Getting the Alt OUT of the V-12 Chassis is Tres Difficile,You'll not be as Unlucky)

http://w140repair.com/Alternator_Bearing_Replacement.htm

MultiMeter (Fluke DMM as an Example) usage tutorial:

http://mechatronics.mech.northwestern.edu/design_ref/tools/multimeter.html

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'84 300SD sold
124.128

Putting the Probes on the Battery without the Engine running and the Key off will tell you the Battery Voltage that on a charged Battery should be 12.50-12.75 Volts.
Ounce the Engine is going and if the Alternator is charging the Voltage will go up to what ever the Voltage Regulator is set up to charge the Battery at. That be at least 13.5-14.50 but most seem to be closer to 13.5 volts than 14 volts.
If it is charging OK the next thing to check is to see if it will continue to charge properly after the Head Lights are on and some of the accessories.

On my Car the charging light never comes on no matter how many accessories I use (my AC does not work so that is not one of the accessores I use); my charging voltage stays at 13.7 and as long as the Engine is running my Charging Light never goes on.

Some members when they are running their accesories and Head Lights when they idle the Charging light goes on but quickly goes off as soon as the Engine rpms go up.
I do not think that is normal but it seems to be OK as long as it does not deaden the Battery.

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84 300D, 82 Volvo 244Gl Diesel

Ill be making that Alternator voltage check as soon as I have a decent charge again on my battery.

From what Ive read here and there, it seems like the voltage regulator brushes often cause insufficient charging. Does it sound like that could be the case?

Yes. That is the reason some have suggested taking off the Voltage Regulator to check the Brushes. If either or both of the Brushes has 2mm or less sticking out the Brushes or the Voltage Regulator should be replaced.

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84 300D, 82 Volvo 244Gl Diesel

It's a good thing Chad and others loaded me up with graphics. Your threads are using them up.
As Sean Connery would say, "One T only please"......{anybody?}

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Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

I have never seen a regulator that gunked up, probably what's jamming the brushes. Soak (overnight) the whole thing in Potassium Hydroxide (Zep Indusrial purple , Purple power, Grease lightning etc), rinse in hot water, then put a tooth brush to it and it should become spotless. See if that restores the spring tension. Dry before install. The brushes can be replaced. They are welded in (soldering iron won't melt it) so drill it out and solder new brushes in. New brushes can be bought from alternator rebuild shops.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Ive got Simple Green and its been soaking for about an hour and already some of the spring tension is restored. Soaking and getting it wet wont do any damage to it?

By the picture in one of the earlier posts on this thread the new Bosch V.R. seems to have a good centimeter or more sticking out of it. I Imagine this would compress in as you install it though.

Is the car rendered incapacitated now without the regulator? Im not going to try and start it while its taken out, but what would happen if I did?

Regulator elec components are hermetically sealed so no worry getting it wet. after drying, spray some penetrating fluid in the brushes and work them up/down to get more of the gunk out. If the brushes have sufficient springyness and length, install in the alternator and see if it charges.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

With all due respect, why put that voltage regulator back in when you are just going to have to replace it soon. At about $30, a cheap and easy replacement.

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"Life is tough...it's even tougher if you're stupid." John Wayne


Dave
Pawleys Island, SC

'79 300CD

Just to see if the regulator was the culprit and whether it was a brush contact problem. If the brush length is under spec, then I would replace just the brushes ($4 or so)

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yes, do not forget about cleaning all the connections of the alternator

1. the 3 pin plug
2. the spring leaf electrode in the alternator (scrape it clean with a flat blade screwdriver) and it's corresponding connection on the regulator (scrape it clean also).

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked