The $500 500SL Offroadster

[Beater400E]

Pretty sure I know what I did wrong. I adjusted the throttle linkage. That was not the issue. Before I installed the W140 ETA I opened it up to inspect and clean it. I'm fairly certain when I reinstalled the right side cover, with the M16/1 actuator, I didn't get the lever arm properly engaged with the pot arm.

Working on pulled it back out to fix that now.

 

[Beater400E]

Ok, got that ETA yanked back out. Sure enough, I had assembled it wrong. Got that fixed and back together and now I have a throttle again.

Just need to throw a few things back together and I'll get it out for a test drive.

 

[Beater400E]

No dice. Same exact issue with the W140 ETA.

Not sure what to try next. I could swap in a different LH to see if that makes any difference. Any other modules I should try swapping? I have spares of everything.

Also, my charging system is definitely no better. I saw as low as 11.8 volts idling with all the lights on. Highest number I can get is 13.8 with everything off and running at 2500+ RPMs. I'll probably try swapping in a different alternator next.

 

[Beater400E]

Ok, I figured it out. It was the LH module. I had a 92 WOT module in there with the upgraded EPROM. It had been fine for probably close to a year, and then it just started doing this surging thing. I swapped in a different 92 WOT LH and the problem is 100% gone.

I don't know whether the issue is the EPROM or the module itself. I may swap the stock EPROM back in and try the first module again. I'd like to isolate it to either the EPROM or the module if I can.

 

[Beater400E]

For the record, LH module that was acting up was a 014-545-18-32 with a date of 92M04. The capacitors were replaced last year, and the EPROM was upgraded.

The module that is not acting up is a 012-545-62-32. It has a stock EPROM, and I don't think I've replaced the capacitors in this one yet.

Just throwing those data points out there for the next guy.

 

[Beater400E]

I swapped the stock EPROM back into the 014 module and took it for a drive. The issue is back. So it appears it was not the EPROM. Looks like the LH module is misbehaving. That's a bummer. Being that this is a WOT module, I'd really like to fix it. I can swap the other one in to resolve the issue on this car, but I only have these two WOT modules and the second was supposed to go in my 400E when I eventually get around to 5.0 swapping it.

Does anyone have any thoughts on what might be wrong with it the module?

I also swapped in a different alternator to see if my voltage would be any different. It seems to be maybe a tiny bit better, but still not great. I did swap my new regulator over to this other alternator as well, so I guess if the new regulator is a dud I could be fighting that.

At idle with the lights off I'm at 13.0 volts. Turn all the lights on and it drops to 12.0. I think the biggest part of the issue could just be that at idle RPM the output is too low to support all the silly lights. As soon as the RPMs rise above 1000, my voltage rises to 13.5-13.7 or so, even with all the lights on. It never goes higher than 13.8.

My battery is pretty discharged right now, so that could be a factor. I'll get it charged back up overnight and test again tomorrow.

I previously had a smaller diameter pulley on my alternator. I think that was causing belt slip at times, but I wonder if the smaller diameter pulley might actually help with this. It would spin at a higher RPM, and might solve the issue.

The obvious answer is to just not idle for extended periods with all the lights on, but this car does a lot of roadside cleanup and rescue/repair stuff in dusty and/or dark conditions, so I really like having all the lights for safety.

 

[Beater400E]

I may try grabbing a 180 amp alternator from the junk yard and see if that helps with the charging system. Looks like some late M113 cars had a 180 amp alternator that might work.

 

[gsxr]

Not sure about the LH mystery. Have you tried resetting adaptation to mean values on the "bad" module to see if that changes anything?

Alternator could be a dud regulator, but first fully charge the battery and see if the issue remains. I use the standard/stock pulley from all M119's with 6-rib pulleys. I wasn't aware of a smaller one, only larger.

I'm also not aware of any alternator larger than 150A that works with our cars - however, I never seriously researched this. If a 180A unit is available, that would definitely be interesting!

 

[Beater400E]

Not sure about the LH mystery. Have you tried resetting adaptation to mean values on the "bad" module to see if that changes anything?

I completely forgot that was a thing. I have not. I'll do that. Just clear all LH codes, and then "clear" code 1, right?

Alternator could be a dud regulator, but first fully charge the battery and see if the issue remains. I use the standard/stock pulley from all M119's with 6-rib pulleys. I wasn't aware of a smaller one, only larger.

I probably need to test my battery and make sure it's actually healthy. I only discovered the smaller pulley thing because mine had a smaller pulley on it for some reason. I had belt slip issues during WOT 1-2 upshifts until I swapped a standard pulley back in. I'm confident the smaller pulley would help, but I really don't want to bring back that belt slip issue.

I'm also not aware of any alternator larger than 150A that works with our cars - however, I never seriously researched this. If a 180A unit is available, that would definitely be interesting!

I was curious whether a higher output option existed, so I did a little digging. I know the 150 amp from an M113 fits, so I thought maybe some other M113 might have a higher output option. I figured if anything would need a higher output alternator it would be an AMG S Class. So I looked up a 2003 S55, and sure enough, it uses a 180 amp alternator. In pictures, it looks like the same frame as the 150 amp. Checking the compatibility of that 180 amp alternator shows it is used on all M113K cars, as well as the 2006-2007 ML500 and R500. So that's what I'll be looking for.

 

[gsxr]

I completely forgot that was a thing. I have not. I'll do that. Just clear all LH codes, and then "clear" code 1, right?

Correct! With SDS (HHT-Win) you can view the actual values, which can be helpful as you can see if adaptation is maxed out either rich or lean (usually it's lean, 0.8xxx).

I probably need to test my battery and make sure it's actually healthy. I only discovered the smaller pulley thing because mine had a smaller pulley on it for some reason. I had belt slip issues during WOT 1-2 upshifts until I swapped a standard pulley back in. I'm confident the smaller pulley would help, but I really don't want to bring back that belt slip issue.

Interesting! If you know the diameter of either one, I'm curious what they are. I had not measured these in the past, nor photographed the differences.

I was curious whether a higher output option existed, so I did a little digging. I know the 150 amp from an M113 fits, so I thought maybe some other M113 might have a higher output option. I figured if anything would need a higher output alternator it would be an AMG S Class. So I looked up a 2003 S55, and sure enough, it uses a 180 amp alternator. In pictures, it looks like the same frame as the 150 amp. Checking the compatibility of that 180 amp alternator shows it is used on all M113K cars, as well as the 2006-2007 ML500 and R500. So that's what I'll be looking for.

The voltage regulator changed on the newer cars, around approximately MY 2000. I never experimented to see if the new VR would work with our older cars. The connector on the back is different. If this does work, that would be awesome.

I believe the newer alternators generally all look like the ones shown below. Note that only 1 wire may be used of the 2-pole VR connector.

 

[Beater400E]

The voltage regulator changed on the newer cars, around approximately MY 2000. I never experimented to see if the new VR would work with our older cars. The connector on the back is different. If this does work, that would be awesome.

I believe the newer alternators generally all look like the ones shown below. Note that only 1 wire may be used of the 2-pole VR connector.

Yeah, I just assumed there was a way to make it work. My biggest concern was whether it would even bolt up. Looks like it should, so I'll give it a shot if I can get my hands on one.

I forgot to mention, another thing I'm going to try is LED bulbs. I usually don't like retrofit LED bulbs in place of factory incandescent bulbs. They never perform the way you'd hope. The thing about the rally lights on this car though is that I don't really use them to light the road ahead. They're mostly just cosmetic, and also add a factor of safety by making the car more visible. They can still do that with LED bulbs.

If I replace the 55w fog light bulbs and the 100w driving light bulbs with LEDs, I expect that will make a big difference. I also have 100w headlight bulbs in the factory housings. I may try some retrofit LED bulbs there as well. I'm less willing to sacrifice real performance there, as you'd imagine, so if I'm not happy with LED headlight bulbs, the 100 watt Hella bulbs might stay.

I expect all those LED bulbs would significantly reduce the demand on the alternator.

 

[Beater400E]

Well damn. Resetting adaptation fixed it.

 

[Beater400E]

MAF strainers had been NLA for a while but are back in stock at dealers. I just picked up 4 from Laredo.

 

[gsxr]

MAF strainers had been NLA for a while but are back in stock at dealers. I just picked up 4 from Laredo.

Nice! Wish these weren't $30 each... sheesh...

000-090-01-45 - Parts Kit, Oil Screen MB Parts Source

Factory Direct Parts Kit, Oil Screen (900145) For Your

www.mbpartsource.com

 

[Beater400E]

Nice! Wish these weren't $30 each... sheesh...

Yeah, still beats the $50 each that everyone else seems to want though. I have a few MAFs on the shelf that I might try to sell. They all have damaged strainers though, so this will solve that.

 

[gsxr]

I have a couple with damaged strainers too. Always nervous about them getting damaged in shipping though. Looks like yours arrived in perfect shape.

 

[Beater400E]

I have a couple with damaged strainers too. Always nervous about them getting damaged in shipping though. Looks like yours arrived in perfect shape.

They did. Laredo stacked them together and then double bagged them before putting them in the box. Pretty decent effort. They arrived in perfect condition.

 

[Beater400E]

The junk yard did not have the 180 amp alternator, so that gets to remain a mystery for now.

I replaced my headlight, driving light, and fog light bulbs with LEDs. Between that and fully charging the battery, I think it's probably good now. Driving with the lights on I'm seeing between 13.7 and 14.0 volts. It never goes above 14.0. That seems to be where the voltage regulator wants to be.

Idling, in gear with absolutely everything turned on high I'm around 12.6-12.7 volts. In park it's 12.9-13.0 volts.

The biggest power user appears to be the climate control blower motor. Idling with the lights on and the AC on with the fan on "4", I'm around 13.0 volts. Reduce the blower to "1", and I jump straight to 13.9. Turning the AC off takes me back up to 14.0, even with the lights on.

The lights were definitely a factor, but that blower motor is eating a ton of power too. It's not blowing a fuse, so I assume it's probably healthy, so probably not much I can do about it.

I also finally replaced the breather hoses from the ETA to the valve cover, as well as the ETA boot and MAF strainer with brand new OE parts. Since I had the ETA out numerous times, the original hose and boot did not survive. They were all rock hard. I had tossed some Uro junk in there short term, but now that everything is sorted the OE parts will keep it happy.

 

[gsxr]

Nice work on the ETA+PCV refresh! The OE parts will last a long time.

Any chance you have a DC clamp-style ammeter to measure current draw?

Sounds like the HVAC blower is the item which pushes the draw beyond what the alternator can provide at idle. The blower likely pulls 20-30A on high, assuming it's similar to the 124 blower. If you are already consuming ±100A with everything else on, adding the blower on max could exceed idle output, which would cause the voltage to drop below mid-13's.

 

[Beater400E]

Ok, this is funny. My cabin air filter was full of dirt. I pulled it out and knocked a bunch out and then blew it out with compressed air. Reinstalled it, and now no matter what I do my volts don't drop below 14.0. I'll order a few new filters and plan to replace it regularly since dusty offroad driving is what this car does.

So that was a key part of my root cause. My charging system appeared weak because of a clogged cabin air filter causing the HVAC blower to draw more amps than normal.

Bonus, my HVAC moves noticeably more air now.