justinp95

So I got the dreaded battery lights, no ac ect. Anyway, Its not the rear battery or the aux battery either. Rear tested ok and aux i replaced. Alternator test came back DIODE OPEN. Is it the alternator or the Voltage regulator????? And which regulator should I buy?

verminator

The voltage regulator's function is to convert the ac output from the alternator to a dc output through a diode rectifier (ac to dc). The dc voltage is what is used in the cars electrical system. The failure mode of the voltage regulator is a diode failure which decreases the power output capability of alternator. The other diodes in the rectifier try to make up for the loss of the diode and get over loaded/stressed and they fail, power quality also gets bad in the car, lots of ripple in the dc...Replace the regulator and you should be good...GL

justinp95

Are there different alternators on these cars? I found the PN for the bosch one, but is there an alternative?

justinp95

Also, FYI test showed " No load, 11.3 V" and " Loaded 11.5 V" if it matters. Seems pretty low.

verminator

So you regulator is shot. There is a great diy posted on the site....search it. There are also allot of posts that describe the smell of melted/overheated alternator insulation, then it is game over and time to replace the alternator. Sounds like you've caught it in time. Don't run it, get the regulator replaced. Look at the sticky for parts and i'm sure the regulator is on there...i can't quote the manufacturer of the alternator but Bosch is likely...regulator is cheap ...$30ish...the alternator is much more...GL

Jelanib

DIY - https://mbworld.org/forums/w211-amg/...lternator.html

VR $33 at Autohaus - http://www.autohausaz.com/search/pn....76&brand=Bosch

turbo97se

Wow ... only $33 for VR on E55? Mine was $70 for E320CDI. I pulled my alternator out though because I tried to replace the whole thing with a re-manufactured one. But the re-man did not work at all. So I just ended up changing the VR ... I still was getting Battery low message but turns out the main battery has a low capacity .. as soon as I switched to 900 CCA battery, no more issues.

Here is my DIY .. it is actually very similar to the E55 in terms of layout ... I had to pull the radiator fan out.

https://mbworld.org/forums/diesel-fo...nator-diy.html

justinp95

Ya i never smelled any burning plastic. Got one for $43 shipped so hopefully its the issue!

justinp95

Replaced the regulator and that wasn't it. Replaced the alternator and now it's at 13.3 while it's on.... What should I check next besides the terminals ?

justinp95

Re tightened battery terminals and it initially went up to 13.7 then started dropping to 13.5.
Key on after this adjustment the battery was at 12.7.

turbo97se

What makes you think things are still not fixed? 13.5 to 13.7 is still in normal operating range with car running. Mine is in this range. Unless you are getting Battery low Convenience features disabled message, this is fine.

Rocman8

Yes you are good to go. Alternator fixed it.

justinp95

Well today on the way home I got the battery light again! Alternator is not charging. It's sitting at about 11.9 running. What should I change now? I hear there is a relay of some sort?

Rocman8

What alternator did you get? Reman bosch? Aftermarket?

justinp95

It was a autozone reman.

Rocman8

Sounds like another bad alternator.

justinp95

As i thought, the Duralast brand is a Bosch Reman unit.

Rocman8

AutoZone has horrible reviews for their alternators. Some don't even work right out of the box. It bay be a bosch core but they definitely don't remanufacture it to high standards.

justinp95

Hmmm, When I looked at the forums I didn't see any bad reviews just a few recommendations. I hit it hard coming out of a gas station before this happened so maybe something just came loose. Ill ramp it tomorrow and swap the voltage regulator just in case.

turbo97se

I had bad luck with a Duralast. Mine, I believe actually caused my radiator fan. Also Autozone only had lower power (150A vs 200A for CDI).

justinp95

Does the W211 have this fuse? X4/10? Im not sure i believe an alternator would just die after a week.


http://www.justanswer.com/mercedes/3...-charging.html

https://mbworld.org/forums/cl-class-...ator-help.html

ZeroE350Seven

Hi, you can request Autozone to bench-test yours at the store.
If the reman. Alternator you just bought was a bad one.

justinp95

Well, thats not really the issue. I already have the replacement ready to go in. The problem is the time and effort to get the damn thing out. I can see its not charging by looking at the voltage gauge. So its the alternator again or there is a fuse somewhere (like the one above) no one knows about.

Mr. CVE

Similar happened to me, met a friend driving the highway, thought I would show him some fun,
and bang the dash went red, and the car into shutdown.

Turned out it was the reg, replaced the reg and was on my way.
If there is no voltage coming out of the alt when running, check the input triggers. if they are there it is a bad alternator.
I tried to pull mine out, but was a pain, ended up doing the reg in the car.

justinp95

Can you explain this a bit more? Input triggers?

check the input triggers. if they are there it is a bad alternator.