Hi Amp Alternator...Good Cold Starts
 

In my 84 300tdt, I just recently had my alternator checked and found that it was not charging well...my battery was recently new (Duralast). I had the battery checked (which died recently on first cold 15 deg F morning) and alternator checked at Auto Zone.

I had been reading up on upgrading from OE 65 amp alternator to a higher amp one, and I decided to get a 120 amp rebuild from Eagle Auto Electric (ebay seller) out in CA. Very good service, fast ship, very responsive to questions, and very high 99.9% rating. Cost is $109.00 plus $20 ship. He assured me that this alternator is a "drop in" even though it is quite a bit bigger than the original. It is also a single stud alternator, so you need to abandon the original harness, and run a new one to the battery pos., as well as connect the blue dash light wire to the small stud.

The alternator replacement went very smoothly....it came with a double pulley, so I didn't have to wrestle with getting the old one off. The new unit dropped right in, did not have to disconnect coolant hose, or anything, to provide access. Went in using original bolts, bracket, and belts...PERFECT!

The voltage on my volt meter registers at a solid 14 to 14.2, even when idling, with a little dip here and there when I turn on rear defroster, or put fan on high...this is normal. But the alternator does the trick keeping voltage solid at about 14.0 plus. Now my cold starts are great...previously I had been running continuously on a partially charged battery...just fine in warmer weather, but as soon as the weather turns cold, starts were very difficult without plugging into a block heater. I also adjusted valve clearances, and I run in winter using rottella 5-40 synth.

I have an aftermarket stereo with a couple of small amps, but no big current draw such as oil heater or such.

The other day, during an overnight trip to Vermont, the car started at 10 Deg. F with only two complete glow plug cycles (when glow plug relay shuts off, not when indicator light shuts off). I just turn the key, wait for it to catch after 4 or 5 turns, then give it fuel and its off and running.

Kudos to Eagle Auto Electric ....very good product at good price...I will now have to wait to see how the alternator lasts.

Fast starter revolutions are a key to good cold starts...a fast starter results in good compression (all else being equal)...sluggish starter due to low battery (due to bad alternator) just wont start the car.

I am now in the process of changing battery cables and ground strap to 1/0 to maximize current to starter. (Previously when jumping the car, I would see smoke from above the starter/cable area...presumably because the pos. battery cable is undersized (4 gauge ?)...so I am going with big moosey 1/0 cables!

For those considering a higher output alternator, I give thumbs up to Eagle Auto Electric...search Ebay for "Mercedes Alternator" and you will see the $109 alternator I bought...good products...he assures me that he uses Bosch parts in his rebuilds.

Regards,

Mark

Yes, any upgrades to the charging system are slick... I've only done my I6 cars at this point, both use the 143A now. HUGE jump from 70A. :)

I'll do the SD when I can remember to do it (the alt I have is a Gold Reman from a local auto store I scored for $9 at picknsteal)

I recommend Eagle, no alternators but have gotten a couple of starters from them.

http://cgi.ebay.com/ebaymotors/MERCEDES-ALTERNATOR-DIESEL-240D-300D-450SL-74-85-120AMP_W0QQcmdZViewItemQQ_trkparmsZ66Q3a2Q7c65Q3a3Q7c39Q3a1Q7c240Q3a1318QQ_trksidZp3286Q2ec0Q2em14QQ hashZitem360112550444QQitemZ360112550444QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

The ad says you can use your own pulley, though. :confused:
Reasonable shipping also.....

Yeah, about the pulley...
 

When I got mine, I expected that it would be without the pulley...I thought he said that he could provide a pulley if I needed a single belt pulley, but not a double belt pulley which I needed...but then the alternator came with a double pulley. I think he only had a couple on hand, but usually doesn't provide the pulley (standard procedure from any place you get an alternator).

Before I purchased the alternator from Eagle, I called them and talked with the owner...just a few questions to see if I would get a "good vibe" about buying one. Thats how we had a discussion about the pulley. And I absolutely did get a good vibe...the owner seems very genuine, wants to put out a good product and wants to please his customers. He even wrote on two post-it notes where to attach each contact post, and stuck the post-its onto the corresponding post, because he thought I wasn't sure about it. Good guy, good product.

The 65 amp OE alternator is grossly undersized for these cars. A higher amp version makes a world of difference being able to rely on having a fully charged battery for cold starts...this makes a huge difference by spinning the starter fast instead of a sluggish mode. Eagle also offers an 80 amp and a 150 amp version. The Eagle guy said he would recommend the 150 only if I had a veggie oil heater and such. The 80 amp version is probably intended for the 240D and even the 300Ds as long as you don't have any current draw beyond OE...in my case I have a couple of small amps for the stereo so I opted for the 120 amp.

Mark

Mark

I never had any problems with mine after I added a second ground wire from battery to intake manifold bolt.
One problem on these cars is after 25 years,the chassis ground is not the best as when new.

you can have a 500 amp alternator it isnt going to cure bad starters, bad batteries or poor compression

Very true. I have an 80A on mine from a saab, and it helps a lot with keeping the system up to proper voltage when using a lot of the high power accessories.....however it still can't quite hold it at idle with everything on....so this year I am on a quest for a 120A unit..... :D :D

How true!
 

Absolutely....a hi-amp alternator is not a cure-all. There are many elements related to poor cold starting discussed at length in this forum....bad glow plugs, poor compression, tight valve clearances, too heavy weight oil, poor fuel delivery timing, carbon buildup in prechambers, bad injectors, bad battery, weak starter, poor engine ground, etc. etc. etc.

In my case, I addressed all of those things, and still had poor starts thinking that the battery was draining (possible short somewhere?). In installed a volt meter in place of the ash tray, and always felt the alternator was fine, with operating voltage aroung 12.5 to 13.5 v. But I always had problems with poor batteries....not enough power to crank the starter fast when cold. In hindsight, I realize that I had been driving around always with a partially-charged battery...this is just fine when weather is warm..the car will still start like a tiger. But with the first very cold day, no start because the starter just doesnt go! I realize in hind sight, that the alternator was the problem, even though the alternator dash idiot light never came on. The 120 amp alternator has made a world of difference. But certainly, all the other factors related to cold starting (discussed in another current very interesting string here) must be addressed...a hi amp alternator by itself will not cure all ills related to poor cold starts.

Mark

The pictures from eagle electric for the 120 and 150 amp looks like an 80 amp alternator. I would like to purchase the 120 amp for the same reason of having a stereo amplifier. Are there any problems using an over-clocked alternator as opposed to using the al129x from saab? My experience with remanufactured alternators isnt good. They dont usually last. The new 65 amp bosch alternator i bought 12 years ago is still going strong.

looking at eagle, I also see that they have the bosch al129x (115A) from the saabs that will go in a w123 for the same price as the 120A.

Is there any reason, connections, brand, otherwise that it would be better to stay with Bosch?

I'm thinking about an upgrade soon.

Yeah, I have been thinking along these lines as well. You know it's time to address charging issues when your blower motor speed varies with engine rpm.

I realize that you're thrilled with the new alternator, but, I have to tell you that the alternator didn't fix your starting problem. The stock alternator provided a system voltage, as stated above, of 12.5 to 13.5V. The only possibility that this voltage level will fail to fully charge the battery is if you have a serious load on the battery (lights, wipers and blower) and don't maintain 1500 rpm. Under this condition, you can deplete a battery and make the morning start more difficult.

But, for most driving conditions, the 65A alternator will do exactly the same as your new alternator...........you cannot force a battery to take a higher charge simply because you have a larger alternator.

One final variable is the voltage regulator. The new one might be turned up a bit so that the voltage is 13.5V to 14.5V. This would provide a better situation for the battery during short trips at lower rpm's.

Be interesting to see the system voltage as measured with the new alternator. I'm betting that it's slightly higher than your posted readings.

An alternator does nothing during starting. All you did was get the battery charged to its proper level.

I used a saab 80 amp alternator and noticed a difference in my cold starts.

I think my old alternator was not fully charging the battery on short city runs with the defrosters on full and lights on.

cant ask it to do more than it can with only 55 amps but the new one seems to top up the battery faster on short runs

I wonder if this is bad for a battery?:confused:

ahh i guess not :D:D

Steve