alternator removal 380sl - PeachParts Mercedes-Benz Forum

slfan · #1 12-20-2010, 12:42 PM

I hope somebody knows the section on the cd which covers the replacement procedure for the alternator on an 84 380sl. Although I could probably figure it out, I would like to verify in the service manual.
Thanks in advance

Walrus · #2 12-20-2010, 03:10 PM

Damned if I can find it...(like a lot of things supposedly in that manual)

Try:http://www.startekinfo.com/StarTek/outside/11883/PROGRAM/Engine/107/M116_38/13-340.pdf

The V-Belts section might help a bit...

slfan · #3 12-20-2010, 07:07 PM

Thanks. I was afraid of that. Oh well, your link identifies the bolts involved. It should not be that complicated.
Do you know, does the pulley pry off? I have not looked at it closely.
Thanks again

Walrus · #4 12-20-2010, 09:20 PM

Quote:

Originally Posted by slfan

...Do you know, does the pulley pry off? I have not looked at it closely.
Thanks again

Sorry... No Idea

Strife · #5 12-20-2010, 11:43 PM

Quote:

Originally Posted by slfan

Thanks. I was afraid of that. Oh well, your link identifies the bolts involved. It should not be that complicated.
Do you know, does the pulley pry off? I have not looked at it closely.
Thanks again

If you are moving the pulley from one alternator to another...(which is the only reason to remove it)...hopefully, there is a hex in the middle of the alternator shaft, which you use in holding the alternator shaft while turning the nut counterclockwise. If not, the fan can be locked with a screwdriver (ugly, but it works). Be aware that this is a VERY tight nut and I'd soak it with PB blaster for at least a day before even trying it - I've had to cut off two of four nuts that I've tried to remove, even after soaking.

When you do get it off, be certain to observe the exact order of parts you remove and replace them in exactly the same order (spacers, etc). Note that the "pulley" is really two stamped halves of sheet metal. Do not allow the woodruff key, if equipped with one, to fall out and get lost from the shaft.

I'd say that 90% of alternator problems can be solved with a new brush/regulator assembly, $30 ($20 if you shop).

Ive gained this experience disassembling and cleaning these alternators, polishing/plating them, and replacing the brush/regulator assemblies.

slfan · #6 12-21-2010, 07:31 AM

Strife,
Thanks for the advise. I'll make sure to have that nut soak overnight.
My car has not had any issues for several years and, other than oil changes, I have not done anything under the hood. Weekend project.

SunGuy · #7 12-21-2010, 12:06 PM

slfan,

How did you determine that the entire alternator was bad and not just the voltage regulator/brushes? You can see the pic of what I'm referring to here...

http://catalog.peachparts.com/ShopByVehicle.epc?q=1984-Mercedes--benz-380sl-Engine--Electrical&yearid=1984%40%401984&makeid=63%40%40Mercedes%2DBenz&modelid=6255%3AED%7C10000052%3AMBC%7C1528%40%40380SL&catid=240798%40%40Engine+Electrical&subcatid=240870@@Voltage+Regulator&mode=PD

slfan · #8 12-21-2010, 09:21 PM

SunGuy,

I was hoping nobody would ask. Oh well.

I have owned this car for just under 10 yrs. During that time I have done many/most of the repairs myself. The service cd became my best friend along with the many lessons from this forum. I posted few questions as most of my questions had been asked and answered by others before. My car has had the usual issues (missing at idle, vacuum issues, frequency valve adjustments, etc.) I cringed whenever I read how some throw parts at a problem without testing.

I have not had a problem for quite a while. When my battery light came on, I linked this to the very recent intermittent bearing-going-out noise and I drew my conclusion. I'm afraid I blew it this time. I should have done some checking. Strife's reply painfully reminded me of the fact that brushes often solve the issue. I had read that before. I'm kicking myself. Oh well. At least it is not as much as a FD or WUR. I'll keep you posted.

slfan · #9 01-02-2011, 06:20 PM

Ok. Installed the new alternator. But now....

After 40 miles or so, battery dead and had it towed home. Took the new alt. out and realized I had forgotten to swap condensers. Prior to re-installing it, I thought I'd have it tested to make sure. It passed.
Obviously had to jumpstart the car. Took it for a spin, less than 3 miles. Noticed radio turned on and off, no blinker, engine hesitating and barely made it home. Same thing, dead battery. The no-charge light, which had come on and made me get the new alternator, is off.

I'm stuck here. Does anybody have any suggestions.
Thanks in advance.

RadioTek · #10 01-02-2011, 08:38 PM

Check your connectors and connections. there may be one in the circuit that has gone on you. Look for missing or loose connections, swollen wires (corrosion inside), "green fur" (copper oxide crystals), and arc tracks or cracked insulation.

What's wrong is probably something simple, but finding it usually isn't.

Best of luck,
Scott

tecqboy · #11 01-02-2011, 09:07 PM

Agree with the above post, especially the negative lead from the battery to the chassis.

slfan · #12 01-03-2011, 08:12 PM

Thanks to you both.
I checked both + and - wires from plug to connectors on the pass. side wheel well for conductivity. Both OK. No signs of deterioration.

Then I noticed my battery sticker "SEP 00"...... Thought I'd better replace that as I had ran it down twice by now.
New battery E/O 12.1 V
Idle and 2000 rpm 12.1 V
Idle with lights and defrost on 11.something V

Conclusion would be bad alternator. It's just that I saw the screen on the tester at Kragen which showed three separate fields "PASS".

Does anybody know what the separate plastic "thing" is, mounted on the alternator, with the single wire plug. Kragen called it a condenser. If that is correct, any way to test it?

Keep you posted.

Strife · #13 01-03-2011, 11:03 PM

Ok ,assuming that this is NOT alternator although the alternator is NOT working...the problem is that it isn't "bootstapping" itself. An alternator of this type needs a GOOD battery and voltage in order to bootstrap itself into operation. So, it's either the battery, or the wiring from the battery to the alternator.

What voltages do you have at the TWO red wires leading to the alternator connector, unplugged from the alternator.

With the ignition ON, what voltage is at the blue wire?

The reason that I ask questions like these is that in a bizzare circumstance, it is possible that the alternator is not getting voltage through the ALT warning lamp, which would prevent the alternator from actually starting the generation of power.

slfan · #14 01-04-2011, 09:55 PM

Strife,
Voltage at each of the red wires, unplugged, I/Off, 12.45
Voltage at blue (looks black to me, the third wire on plug) I/On, 12.12.

I noticed when all is hooked up, I/on, I do not have the red battery light come on. I thought it always did. Isn't it supposed to be on prior to cranking?

slfan · #15 01-16-2011, 09:14 PM

Yup, I now know I have been throwing parts at it.

I had both alternators tested. Both old and new are good. So the problem is elsewhere.
Wires all have continuity. I checked the electric schematic and do not see a fuse anywhere connected to the charging system (it couldn't be that simple). With battery disconnected, I have continuity between the blue wire from the alternator plug and engine (ground). Does that sound right?