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  #1  
Old 09-05-2010, 03:58 PM
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1985 300D Turbo Alternator Replacement

I pulled my alternator out and had it tested at a local parts store-failure.

1. Should I trust this test? Should I know more about that before I go buying a new one? I was having electrical/starting problems, so it makes sense, but....?

2. If I replace it, should I go with a Bosch 65amp alternator? Or can I use AC Delco warrantied replacement from my local parts store?

3. Money- I shouldn't pay more than ? for a new/rebuilt alternator?

Please advise.
Thanks.
Jay

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  #2  
Old 09-05-2010, 04:17 PM
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I am assuming you issue was no charging.

You could take it to an other store and have it tested again. If both places say it is no good it most likely is no good.

Unscrew the 2 screws that hold on the Voltage Regulator. If what is left of the 2 Brushes is worn 2mm or less it the Brushes are worn out.

If the Brushes are worn you might consider replacing only the Brushes or the Voltage Regulator. Of course you would be taking a chance that the Voltage Regulator is the problem so you might spend for a new Voltage Regulater only to find something else is wrong.

Are the AC Delco Alternators ones that are rebuilt by AC Delco are are they new alternators?

Please remember this; if you buy a rebuilt Alternator have them test it before you leave the store to make sure it works. Along with the above, rebuilt Alternators often do not come with the Pulley. Have the Parts store remove your Pulley from the Old Alternator and install it on the New Alternator and have them test the New Alternator.
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  #3  
Old 09-05-2010, 04:48 PM
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Quote:
Originally Posted by wordmanjay View Post
Money- I shouldn't pay more than ? for a new/rebuilt alternator?
I suspect that you will be hard-pressed to find a new alternator, regardless of how much you are willing to spend.

Quote:
Originally Posted by wordmanjay View Post
I pulled my alternator out and had it tested at a local parts store-failure.
Did you get any details on the test results?
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  #4  
Old 09-09-2010, 10:29 PM
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good replacement alternators...good upgrade

Check out Eagle Auto Electric, Inc...do internet search on that name and they will come up. They sell via Ebay, or direct credit card over the phone. Very good product...I put the 120 amp version in my 84 123 wagon a couple of years ago, and it is great. It is larger than the original (undersized) 65 amp, but does drop right into place with no modifications needed for mounting. You do need to modify the wiring, but this is very easy. These are very reasonably priced and a very good product, and very good service. The guy answers all question over the phone, very helpful, and his admin/shipping people are great.

I have an after market stereo with a couple of small amps in my car which draw extra current (beyond design specs) and I could have the stereo on, ac on, headlights, etc., and I my headlights never dim, and I have solid 14 volts when car is running no matter what, even at idle. Great product, great company.

Mark
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  #5  
Old 09-09-2010, 10:35 PM
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if you have the alternator in your hands, pull the two screws out of the black voltage regulator and look at the brush length, and also look at the shape of the brushes. if they are smooth worn with a full width curve the alternator can take another regulator for about 40.00 and you'll be back as before. if the ends have a sharpened look to the curve, then the ring in the armature is worn poorly, and probably can't be reused without turning and having a larger regulator installed... not worth it.
the saab 90 and 120A alternators bolt in, and just need wiring changes. the MB 80 and 90 amp alts bolt right in and connect to the existing wiring harness. you choose.
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  #6  
Old 09-09-2010, 11:52 PM
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vstech - are these beyond hope (as an example, sorry to hijack):




Also, you mention the 80 and 90A alternators that connect right in using the MB harness - which car would I look for to get one of those? Makes it easier than the saab application if it truly directly fits...
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  #7  
Old 10-03-2010, 03:48 PM
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Diesel911 & Vstech,

The stock Bosch alternator for the 85 has an internal regulator, right? Are you recommending replacing just the regulator? Also, I thought the Bosch came in a 55a version as well as 65a, if I am measuring only 12.6-8V at idle, does that tell you my alternator is going bad or perhaps expected on a 55amp.
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Current wives...
2000 ML430 Skyview "The Mel"
2000 CLK430 Cab "The Cab"
85 300D Turbo "The Diesel"

Past wives...
92 300E
85 190E

"One should as a rule respect public opinion in so far as is necessary to
avoid starvation and to keep out of prison, but anything that goes beyond
this is voluntary submission to an unnecessary tyranny, and is likely to
interfere with happiness in all kinds of ways."
Bertrand Russell
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  #8  
Old 10-03-2010, 04:43 PM
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At idle with what on? Nothing? Lights? Ac? Radio?

If loaded with some of that stuff, I'd say no big deal, 12.6-8 is normal... Maybe not optimal but possibly normal. If nothing is on and you're seeing that, I'd say dirty connections, bad regulator, etc could be the issue.
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Current Diesels:
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  #9  
Old 10-03-2010, 05:13 PM
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Quote:
Originally Posted by ML Dude View Post
Diesel911 & Vstech,

The stock Bosch alternator for the 85 has an internal regulator, right? Are you recommending replacing just the regulator? Also, I thought the Bosch came in a 55a version as well as 65a, if I am measuring only 12.6-8V at idle, does that tell you my alternator is going bad or perhaps expected on a 55amp.
That's the regulator in the above pic, make sure you don't need just that, a five minute, two screw swap.
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  #10  
Old 10-03-2010, 10:26 PM
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JHZR2, I'm hoping a bad ground and loose connection that I found may be the cause of what appears to be an intermittent discharge issue.

Toomany, I was curious if it made sense to take worn brushes or old regulator and replace just that. I too am being told my alternator is failing a test, yet it seems to power my car and recharge my battery, most of the time.

The curious thing to me was low voltage readout from the alternator however the parts shop guy only did an idle test, I'm going to retest at 2000rpm
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Ed "Don't Benz's just feel better..."

Current wives...
2000 ML430 Skyview "The Mel"
2000 CLK430 Cab "The Cab"
85 300D Turbo "The Diesel"

Past wives...
92 300E
85 190E

"One should as a rule respect public opinion in so far as is necessary to
avoid starvation and to keep out of prison, but anything that goes beyond
this is voluntary submission to an unnecessary tyranny, and is likely to
interfere with happiness in all kinds of ways."
Bertrand Russell
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  #11  
Old 10-03-2010, 11:45 PM
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Test the alternator under load. Headlights (brights), AC, fan etc. The stock alternators are regulated @ 13.8 volts. That will go down under load as you are drawing more amps. Anything under 13.1 is unacceptable in my opinion. Others will say 12.8. A fully charged lead acid battery should read 13.2 volts. (2.2 per cell) Max charge rate is 2.35 per cell. (14.1 volts) Modern cars are regulated at 14.1 volts. The voltage reading is only telling you half the story. Where are the amps (flow) going? Into the battery? (good). Out of the battery? (bad). With an older car the wires have built up a resistance over the years. Couple that with an alternator that is only putting out 13.8 volts and you're always on the edge of acceptability IMHO. Good thing we have such large batteries in our cars. It's going to start getting cold so the electrical system will be working harder to get the car started in the morning. Glow plugs, cold cranking amps, etc.. The alternator is rated in amps. Stock is 55/ 65. You should have a 50% safety margin to make sure you have enough amps to charge the battery while you are using the other 50% for your lights, fan, sub woofer, blah blah, etc...... That means on a 55 amp alternator you should not draw more than a 27.5 amp continuous load in order to safely insure that your battery will get charged. Have Fun
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  #12  
Old 10-04-2010, 10:04 AM
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At the normal 750 rpm, I usually get 14+ volts.

You can try a new regulator (won't hurt to have an extra around), or have a test performed on your system, free at most AutoZoo's, they can tell you what part of the system needs attention.
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  #13  
Old 12-07-2011, 08:06 PM
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ALTERNATOR TESTS ON DIESELS

Don't let anyone tell you alternator is bad, at idle, until glow plugs are off - 2 minutes to be sure. My 300D has had 3 new alternators, 1 for each PO, and tested bad recently at Advance and Autozone until I waited a minute or so. Stock alternator can't handle glow plugs at idle!!

Dick
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  #14  
Old 12-07-2011, 08:17 PM
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Quote:
Originally Posted by PROF59 View Post
Don't let anyone tell you alternator is bad, at idle, until glow plugs are off - 2 minutes to be sure. My 300D has had 3 new alternators, 1 for each PO, and tested bad recently at Advance and Autozone until I waited a minute or so. Stock alternator can't handle glow plugs at idle!!

Dick
Quote:
Originally Posted by wordmanjay View Post
I pulled my alternator out and had it tested at a local parts store-failure.
I tend to doubt that the OP took his glow plugs with him to the local parts store for the alternator test................

I'm also quite hopeful that the OP resolved his issue now that over one year has elapsed.

Outside of that............welcome to the forum.............
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  #15  
Old 12-07-2011, 11:44 PM
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Quote:
Originally Posted by ML Dude View Post
Diesel911 & Vstech,

The stock Bosch alternator for the 85 has an internal regulator, right? Are you recommending replacing just the regulator? Also, I thought the Bosch came in a 55a version as well as 65a, if I am measuring only 12.6-8V at idle, does that tell you my alternator is going bad or perhaps expected on a 55amp.
That is basically the Battery Voltage.

I believe 13.3 Volts is the absolute minimum voltage when it is charging. 13.5-14.5 would be better.

Comment on rebuilt Alternators.
I had a bearing go bad in my Alternator about 2 years ago. When I pulled the Alternator it had a rebuilt by Bosch Noth America sticker on it.

The Bearings inside were made in China.
So if Bosch is cutting corners you can imagine what the other rebuilders are doing.

Since on eBay new Made in China Bearings were only $2.50 each shipped I bought two sets.
If the new set of Made in China Bearings goes bad I will replace them with the 2nd set I bought or up grade to a higher out put Alternator.

The good thing about taking the Alternator out of the Car and having it tested is that when it is tested the Wiring and groud are going to be OK. So it sort of tells you if you have a possible wiring issue.

If you do not trust one test take it for another free test some place else and get another opinion.

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Last edited by Diesel911; 12-07-2011 at 11:54 PM.
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