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  #1  
Old 01-01-2001, 02:21 PM
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Location: Tribune, Kansas. I farm for a living. I fly R/C airplanes for fun.
Posts: 53
Hello:

First, I did a search on alternators and batteries, but did not find an answer to my question. And the question is... Is there a way to check the voltage regulator to see if it is bad or the windings in the alternator? I was wondering whether to buy the regulator assy or get another alternator?
Thanks

I forgot to say that it is for a 1986 300E.

[Edited by Ron Miller on 01-01-2001 at 01:36 PM]
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Ron Miller

1986 300E
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  #2  
Old 01-01-2001, 02:54 PM
shoe's Avatar
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Without the equipment to test on car no. But you can remove it and take it to most any part's house and the should be able to load test it for you, and free of charge.
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Keith Schuster
2006 E350 98K miles
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  #3  
Old 01-01-2001, 04:44 PM
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You can check battery voltage with the car running and all the lights on, radio on, etc, etc. Note the voltage. Then, turn off all the lights and radio, etc, etc. Note the voltage. With a strong battery/alternator, the variation should not be much. It is a very basic test but, it will give you a rough idea where you are. Another thing you can do is take the regulator with brushes (they come as a unit) out of the back of the alternator (2 screws) and check the length of the brushes. When they are new, they are about an inch long. If they are short or close to the base, replace them.
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  #4  
Old 01-01-2001, 05:14 PM
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There really isn't anyway to test the regulator except as a unit with the alternator. As such, one always takes a risk when just installing a regulator/brush pack.

Since a new/rebuilt unit will include a regulator this is where the risk comes in. I would suggest removing the regulator, examine the brushes, BUT pay close attention to the commutator ring where the brushes ride. If they are grooved heavily the risk is too great. The armature is probably only usefull for two sets of brushes and the second will probably last 50% less long.
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Continental Imports
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  #5  
Old 01-02-2001, 12:20 AM
dlswnfrd
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Re-Built or New

Ron, I have a '87 300E and at about 150,000 miles I started to have low battery charge problems. The CHECK ENGINE light comes on with low voltage. The Regulator/Brush assembly was replaced. In the middle of a short trip the front bearing failed on the alternator the bearing had 150,000 miles too. A re-built from Pep-Boys was installed. After the trip the belt slipped. They broke the tensioner. Pep-Boys paid for the repairs. Another 3 months their alternator failed. Lifetime warrantee, pay the labor $57.00. Another 4 months, failed again, paid the labor. Another 2 months paid the labor, but arranged for a M/B rebuilt alternator, bought the M/B alternator but Pep-Boys would not refund my money only replace with their alternator, paid the labor. Now I have spent the cost of the off brand alternator and of the M/B alternator plus 3 labor charges. At last I had a M/B rebuit alternator. 6 weeks and the M/B alternator failed. M/B said it was a bad Battery all the time. I had a New Interstate M/B battery when this all started. It was replaced under warrantee but to an even higher capacity for a Benz. My Dealer contacted M/B and explained my troubles and M/B gave me a new alternator No charge. Troubles Fixed. You add up the costs, it makes me sick. At the beginning the Benz Dealer close to me the alternator was out of stock. Had I waited one more day? Do it again, NEW garranteed 12 months parts and labor world wide. Happy Trails Beep Beep from smarter now Houston.

Donald.
Newer than New
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  #6  
Old 01-02-2001, 01:01 AM
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Location: Tribune, Kansas. I farm for a living. I fly R/C airplanes for fun.
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Thanks everyone for responding. Donald, I have had rebuilt parts too for my GM and Ford vehicles in the past. Most noteably, I have a 1986 Olds Delta 88 in the garage here. I had a shop put three rebuilt water pumps on in a 2 year period and then bit the bullet and bought a new one. The new one was bought in 91, and is still on the car today. I just looked at my Mercedes alternator, and there is a remanufactured tag on it. I may just spring for a new one now and hopefully eliminate many headaches.

One thing that puzzles me still, I put another known good battery in with 13+ volts. When I turn the key to on position, my abs light flashes 3 times and the o2 light comes on, but none of the other cluster lights come on? Is this because I still have a bad alternator installed? Or another problem?
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  #7  
Old 01-02-2001, 09:04 AM
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Your lack of warning lights concerns me. The activation current for the alternator goes through the warning light/lights. It's possible that your alternator could not be "turning on".

In looking at a diagram low oil, low coolant, low wind/wash, low fuel, charge, brake, and low pad indicators all power up the alternator with power originating at fuse# 5. ABS and O2 are powered separately.

You need those lights to work for your alternator to function properly.
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  #8  
Old 01-02-2001, 10:34 AM
dlswnfrd
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Bit The Bullet

Ron, your past luck is as mine. If you have any miles and/or years as I had on the original alternator, replacing the Regulator/brush assembly and the rest is original, well you get the picture. The only true way to test your battery according to what the Interstate Battery people told me, is to completely discharge your battery, then recharge at a low ampere input i.e. 1.5-2 amperes using an automatic charger that will reduce the input when the battery is completely charged. Then using a hydrometer test the specific gravity of each cell. The cells should test 1.275-1.300. The difference between each cell is to be no more than 0.025. My electrical problems are behind me, and what a good feeling it is. Happy Trails Beep Beep from Houston.

Donald.
fully charged
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  #9  
Old 01-02-2001, 09:45 PM
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Location: Tribune, Kansas. I farm for a living. I fly R/C airplanes for fun.
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My #5 fuse looked ok, but I put in a new one anyway and no change. I noticed a spark when I disconnected and connected the battery today. So, I loosened my belt and turned the alt with the battery hooked up. Felt like there was a catch in the alternator. Also, the pulley was warm, and I had not started the car. I disconnected the battery and turned it again, no restriction at all. So I removed the alternator, hooked up the wires and battery, and grounded the alternator body on the exhaust manifold. It sparked. I held it tight against the manifold, and turned the alt again, felt the same resistance again, pulley got warmer, and I noticed the bearing end of the alt getting warm also. I took the alternator into the local repair all garage here, and their tester said it put out 10 amps through the regulator, and 18 amps without. He said it should put out ~70 amps. Also, he said it was whining bad, like when the triodes go out.

So after all the above descriptions, can the alternator cause all my problems, or am I going to have to replace the alternator and see what happens? Thanks everyone for your help and patience.
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  #10  
Old 01-03-2001, 12:28 AM
dlswnfrd
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d.c. raltermotonator

Ron, have ever noticed labels instructing not to charge a dead battery with the engines alternator? The reason is for the alternator to operate it must had a minimum of 12 volts D.C. This voltage is to excite the field coils. Dead battery and no excertation, no out put. Low field coil volts and over worked and overheated coils. In your case the field coils seam to be excited from a failty regulator. Your alternator is trying to motor. Do yourself a favor and go to M/B for a new alternator(you will have to remove your old pulley and install it on the new alternator, and the new one doesn't use the pulley shaft key).Happy Trails Beep Beep from charged up Houston.

Donald.
no motor in my alternator
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  #11  
Old 01-09-2001, 03:29 AM
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Location: Tribune, Kansas. I farm for a living. I fly R/C airplanes for fun.
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Well, another alternator fixed my problem. It's a good thing I didn't spring for just the voltage regulator and brush assy, because after removing my alternator and looking inside, the windings were fried to a crisp.

Ahhh, never the cheap way out for me it seems. But, my father in law, a farmer, I swear if it was his he would wrap a piece of baling wire around it and it probably would have worked. Ha ha. Thanks everyone for your help and responses.
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1986 300E
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  #12  
Old 01-09-2001, 04:50 PM
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Ron, you've just reinforced my buddy's saying "Good things aren't cheap, and cheap things aren't good.

BCingU, Jim
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  #13  
Old 01-10-2001, 09:07 AM
dlswnfrd
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Ron

As we all learn, the heart to our Benz is the electrical system. And it's heart is the alternator and the battery. Don't EL CHEAPO as I did in the beginning, go first class, use a NEW Benz alternator. Happy Trails Beep Beep from First Class Houston.

Donald.
the hard head
but no more
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  #14  
Old 01-11-2001, 01:03 AM
dlswnfrd
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Ron Miller

No big deal, but in one of your postings you mentioned a Triode in your alternater. I believe it is a diode trio, or three diodes. Happy Trails from us dumbies Houston.

Donald
do it right the first time
and only once
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  #15  
Old 01-11-2001, 07:56 AM
LarryBible
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I agree with Donald regarding alternators, I think.

I definitely think that buying a rebuilt alternator for your Benz from your neighborhood auto supply is a waste of money. I don't, however, buy them from Benz. I have had great success with Bosch certified rebuilt alternators and starters.

You won't go wrong with Donald's suggestion, but I think the Bosch certified rebuilt will also get the job done.

Everyone have a great day,
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