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  #1  
Old 12-13-2020, 10:54 AM
dkr dkr is offline
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Cold Starts

The alternator on my 1984 300D stopped putting out so I replaced it a few weeks ago with a rebuilt 120Amp Bosch unit. I believe 120A is about the largest you can get without replacing the OEM wiring. My car has always started just fine, although recently it would struggle a little bit in the morning on a cold start. This is in Southern California and I am at almost 100K miles on the last set of glow plugs. Regardless of whatever I have done, it has always been a tad sluggish on cold starts.

Anyhow, since I put in the new alternator, it now jumps on from cold. I'm impressed with just how fast it is starting. I see all of these threads about people having issues with cold starts in cold weather and I just wanted to post this because I wonder if just having a better alternator and a less drained battery would be a big help. I have also noticed the blower motor seems to put out a bit more power for the heat.


Dkr.

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  #2  
Old 12-13-2020, 12:09 PM
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The larger "Internal Fan" style alternators actually charge at 14.4V instead of the lazy 13.2-13.5V that the older "External Fan" style max out at. The result is brighter headlights, stronger blower fan, and a more fully charged battery.
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  #3  
Old 12-13-2020, 04:54 PM
dkr dkr is offline
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Yeah, I was thinking about the battery aspect. My last battery lasted just under four years. I wonder if I may get more lifespan with a higher powered alternator. I'm surprised I have never heard of anyone mentioning that before. I always thought high powered alternators were just for sound systems. I didn't realize there would be other benefits for a W123.

Dkr.
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  #4  
Old 12-13-2020, 06:27 PM
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Quote:
Originally Posted by dkr View Post
The alternator on my 1984 300D stopped putting out so I replaced it a few weeks ago with a rebuilt 120Amp Bosch unit. I believe 120A is about the largest you can get without replacing the OEM wiring.

So after reading your message and out of curiosity, I checked the major auto parts retailers online for an alternator for my 1983 300D that would put out 120 amps. The results for range of output were 55 amps to 70 amps. So, my two questions:
1. What is the process for finding a 120 amp unit? Perhaps by entering one's vehicle's specifications, a 120 amp unit is excluded since it wasn't considered within specifications by M-B?
2. Are the mounts and belt configuration for the 120 amp unit identical to the lower amperage specified unit?

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  #5  
Old 12-13-2020, 08:37 PM
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Originally Posted by dogguy View Post
So after reading your message and out of curiosity, I checked the major auto parts retailers online for an alternator for my 1983 300D that would put out 120 amps. The results for range of output were 55 amps to 70 amps. So, my two questions:
1. What is the process for finding a 120 amp unit? Perhaps by entering one's vehicle's specifications, a 120 amp unit is excluded since it wasn't considered within specifications by M-B?
2. Are the mounts and belt configuration for the 120 amp unit identical to the lower amperage specified unit?

I have seen 80 and 100 amp Alternators for my 84 300D on eBay That use the stock electrical connector.

There is even some 100amp ones listed as new. The new ones I suspect are made in China.

Note many years back I bought a New Chinese made Alternator for my Van and it has been charging fine. That must have been 10 years ago.
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  #6  
Old 12-13-2020, 08:58 PM
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Originally Posted by Diesel911 View Post
I have seen 80 and 100 amp Alternators for my 84 300D on eBay That use the stock electrical connector.

There is even some 100amp ones listed as new. The new ones I suspect are made in China.

Note many years back I bought a New Chinese made Alternator for my Van and it has been charging fine. That must have been 10 years ago.

Ok, good to know. Thank you for clarifying.
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  #7  
Old 12-14-2020, 01:24 AM
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Originally Posted by dogguy View Post
Ok, good to know. Thank you for clarifying.
There was what past members who bought from them said was a good quality rebuilder that sold the 80+ amp Alternators on eBay here in CA. Eagle Electric.

When I looked 3 weeks or so ago I could not find them selling on eBay.

In the past for the older AC Delco Alternators that had the internal Voltage Regulator you could by an higher amperage kit that had a new Stator and Rotor.
I did some internet searching and could locate no one selling that same sort of kit for Bosch Alternators. So I am wondering who Eagle Electric bought those parts from?
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  #8  
Old 12-14-2020, 01:33 AM
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On eBay but you need to change the wiring as it won't use the stock connector.

150 AMP Mercedes Alternator W116 W123 W115 W114 W111 107 High Output Generator

US $198.49 + $20 shipping.

The claim is that it would be compatible with my 84 300D. However some of our members have said one of the AC hoses is close to the back of the Alternator. I don't know if all of the W123s have the same AC hose routing.

Note this is in the Ad: "Please let us know if you need a Single V Pulley or Double V Pulley."

Anyway 2 expensive for me.
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  #9  
Old 12-14-2020, 02:15 AM
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They have a 120amp alternator for these?! Wow! I want one, especially if it has an internal regulator that puts out 14.5volts. But honestly how much of a load are you putting on an alternator with single starting battery? Are you charging a secondary bank or running an inverter? The glow plugs are no more than 50 but that’s intermittent. 120amps seems excessive unless you have 60 amp Continuous load. I doubt you could get a small starting battery to accept an 80 amp load for more than 30 seconds unless it were completely flat or it’s lithium.
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  #10  
Old 12-14-2020, 03:25 AM
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When I had my w123, I replaced the alternator with one from a gasser w126. I forget the amperage, but it was higher than the ones for the om617. it worked very well. Brighter lights, HVAC fan did not pull the system down, etc.
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  #11  
Old 12-14-2020, 08:54 AM
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Quote:
Originally Posted by Diesel911 View Post
When I looked 3 weeks or so ago I could not find them selling on eBay.

In the past for the older AC Delco Alternators that had the internal Voltage Regulator you could by an higher amperage kit that had a new Stator and Rotor.

I did some internet searching and could locate no one selling that same sort of kit for Bosch Alternators. So I am wondering who Eagle Electric bought those parts from?

On eBay but you need to change the wiring as it won't use the stock connector.

150 AMP Mercedes Alternator W116 W123 W115 W114 W111 107 High Output Generator

US $198.49 + $20 shipping.

The claim is that it would be compatible with my 84 300D. However some of our members have said one of the AC hoses is close to the back of the Alternator. I don't know if all of the W123s have the same AC hose routing.

Note this is in the Ad: "Please let us know if you need a Single V Pulley or Double V Pulley."

Anyway 2 expensive for me.

Thanks for looking into this and sharing the information! Very helpful, fascinating, and fun!
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  #12  
Old 12-14-2020, 10:42 AM
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Quote:
Originally Posted by Diseasel300 View Post
... "Internal Fan" style alternators actually charge at 14.4V instead of the lazy 13.2-13.5V that the older "External Fan" style ... a more fully charged battery.
So, it isn't the current output, but rather the setpoint of the internal voltage regulator. That makes sense. My other vehicles (Chrysler) show 14.3 V with the engine running. I think that is standard for voltage regulators. 13.5 V sounds low. I'll have to check my 300D's, but vaguely recall I've seen the normal 14.3 V. You don't want >15 V since that can start dissociating the water in the battery to H2 & O2.

If yours is low, perhaps swapping in a new Vreg/brush kit will fix it. You can do that with the alternator in the car, and the part cost ~$15.
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  #13  
Old 12-14-2020, 11:57 AM
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Originally Posted by BillGrissom View Post
So, it isn't the current output, but rather the setpoint of the internal voltage regulator. That makes sense. My other vehicles (Chrysler) show 14.3 V with the engine running. I think that is standard for voltage regulators. 13.5 V sounds low. I'll have to check my 300D's, but vaguely recall I've seen the normal 14.3 V. You don't want >15 V since that can start dissociating the water in the battery to H2 & O2.

If yours is low, perhaps swapping in a new Vreg/brush kit will fix it. You can do that with the alternator in the car, and the part cost ~$15.
When cold, the External-fan Bosch alternators do charge around 14V. They are designed to droop when they get hot. Replacing the regulator/brush assembly will not fix the issue since they are performing as designed. Lousy design and something that designers of voltage regulation equipment have tried to get away from for over 50 years. The later Internal-Fan alternators are designed NOT to droop.
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  #14  
Old 12-14-2020, 12:01 PM
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Quote:
Originally Posted by 240D.Bill View Post
They have a 120amp alternator for these?! Wow! I want one, especially if it has an internal regulator that puts out 14.5volts. But honestly how much of a load are you putting on an alternator with single starting battery? Are you charging a secondary bank or running an inverter? The glow plugs are no more than 50 but thatís intermittent. 120amps seems excessive unless you have 60 amp Continuous load. I doubt you could get a small starting battery to accept an 80 amp load for more than 30 seconds unless it were completely flat or itís lithium.
The later diesel cars have afterglow and definitely need more than the stock 80A alternator can provide. My 350SD draws so much power during the first warmup of the day that the wipers will nearly stall until the glow plugs drop out (glow plugs draw ~70A on a 6 cylinder). Swapping in a later 140A alternator eliminated that issue. I see no reason why an older car would need "more capacity", but the upgrade in voltage regulation is worth it.

Be aware that the newer "internal fan" alternators use ring terminals for their main connections instead of the single latching spade plug of the older ones. You will have to modify your wiring harness with ring terminals (which are better anyway) if you want to upgrade to a newer alternator.
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  #15  
Old 12-14-2020, 01:19 PM
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Am I wrong in thinking ( from what I've read ) that an internal fan 120 amp alternator gives no real benefit for night time driving and/or battery charging than the stock 90 amp internal fan alternator? ( If no modification to increase amperage demand )

Just want to make sure there is no benefit in changing my stock 95 E300D one.

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