300E - is it the alternator? - PeachParts Mercedes-Benz Forum

raysea390 · #1 11-23-2007, 02:16 PM

Just as I was pulling up to my house the other day, the ABS warning light came on and the radio started cutting out.

Up till then, when I first started the car the alternator would not charge unless I revved the engine above 2500 rpm - I could tell when the alternator kicked in because the interior light got much brighter. If I did not do this, my ABS light would come on (the owners manual says it will do this if there is insufficient volts in the battery). The battery was definitely low this morning when I started the car and the trick with the alternator did not work. The battery is less than 2 months old.

So my first guess is the alternator finally packed it in…could it be anything else?

TX76513 · #2 11-23-2007, 02:19 PM

What you described is the symptoms of low voltage and the same symptoms mine had when the alternator went south. The good news a new brush pack is not that expensive and easily installed without removing the alternator from the car.

raysea390 · #3 11-23-2007, 02:31 PM

Thanks TX - I like the 'not too expensive' part! Are the brushes an MB dealership part and is the procedure written up on this forum somewhere?

TX76513 · #4 11-23-2007, 02:39 PM

The part can be purchased at the "BUY PARTS" tab on the top of your screen. For a W124 it's going to be $29 -$35. Do a search for regulator. I would be afraid to even guess what the dealer would want.

There are numerous write-up on the forum. Fairly cut and dry. Remove the 3 spade connector by pulling it off. Take out 2 screws and the brush/regulator pack will drop out. I use a piece of dental floss to compress the new carbon brushes, place back into alternator then pull the floss out. Put the two screws back in, plug in the spade and your done.

You can validate that this is your problem by checking the voltage at the battery with the car running. Should be over 13.4V.

Zeus · #5 11-23-2007, 02:54 PM

Raysea - if that is the original 70A alternator, it is garbage! You need to replace it with the upgraded 80A version. It is not just the extra 10A output, the updated 80A alternator puts out significantly more current at low RPMs, the stock 70A alternator needs to rev relatively high to produce anything near its rated output.

I learned this the hard way on my 300E. Put in the new 80A and you'll never have a problem again (and no dimming lights, ever, like in the winter when you are idling and turn on the rear defrost

).

FastLane seems to only offer the 80A for your car year, which is good!

Here is a pic - you'll need to re-wire it slightly, but it is very easy to do so. Probably a 10 minute job to re-wire and about 30 minutes total to replace the alternator. You don't need to pull the belt, just loosen at the alternator mounting and you can slip the old one out and the new one in with a prybar, easy job. If you need directions how to re-wire, just PM me, or do a search, I think it is covered here somewhere...

raysea390 · #6 11-23-2007, 02:53 PM

Thanks again TX - the brushes are not on the BUY PARTS site but i sent them an inquiry anyways.

If it comes down to it, they do offer a refurbished alterntor - how do i determine if i have the 70 amp or the 80 amp alternator?

TX76513 · #7 11-23-2007, 03:23 PM

That's a good point you brough up Zeus. I am playing with a project that turns the standard Bosch 65a to a 110a. Best part, no rewiring just plug and play.

Zeus · #8 11-23-2007, 03:32 PM

Quote:

Originally Posted by TX76513

That's a good point you brough up Zeus. I am playing with a project that turns the standard Bosch 65a to a 110a. Best part, no rewiring just plug and play.

Cool, you should post some pics when you're done!

TX76513 · #9 11-23-2007, 03:36 PM

Going to - found out there is a JD alternator that is the same case size as my Bosch. Just a matter of switching the guts out. What's great is the diesel tractor alternators put out the amps on low rpm - and that's exactly what we need. There have been some who have done this with the SAAB alternator, but it doesn't delivery that idle amp output.

raysea390 · #10 11-23-2007, 03:36 PM

I'm afraid finances are going to dictate that I just replace the brushes/regulator for now - just got a quote of $22 from a local alternator shop. He didn't ask which alternator i had - 70A or 80A - so I'm guessing its the same brushes/regulator for both. I will probably take the old part off and take it with me to his shop to make sure i'm getting what i need.

TX76513 · #11 11-23-2007, 03:39 PM

Examine the metal contact arangement on the business end on the regulator and make sure they are the same. I have argued this point here sooooo many times that there are some differences in the brush packs.
What Zeus said is true, guess we are all fighting that battle - more power!
Good Luck

raysea390 · #12 11-23-2007, 05:04 PM

Well I called Tysinger, an MB dealership in the Tidewater area, to see if there was a difference. You can actually still order the brushes for $12 - 2 day delivery, or the regulator is $75 with the brushes. I asked if it mattered that i had a 70A or a 80A alternator but they only have one part number for my year (1987).

Anyway, I'm not going to shell out $75 if i can get a regulator with brushes elsewhere for less than $30 and I would rather spend $30 than $12 just to replace the brushes...but i will definitely take the existng regulator with me.

I was a little confused when i told the MB parts guy i had an '87 300E - he asked if the engine was a 3.0 - aren't all 300E's 3.0 litres?

Zeus · #13 11-23-2007, 05:29 PM

Quote:

Originally Posted by raysea390

I was a little confused when i told the MB parts guy i had an '87 300E - he asked if the engine was a 3.0 - aren't all 300E's 3.0 litres?

Some 300E's have the 2.6L engine.

raysea390 · #14 11-23-2007, 05:35 PM

Then that's a 260E isn't it?

Zeus · #15 11-23-2007, 05:40 PM

Quote:

Originally Posted by raysea390

Then that's a 260E isn't it?

Lol, you'd think so! But no, it's badged 300E, just has a 2.6L inline 6 under the hood.

Check out the full list here, scroll down to 'models' -

http://en.wikipedia.org/wiki/Mercedes-Benz_W124