[illstplaya]

There's a TL;DR at the bottom.

Today I walked up to my car, unlocked it and got in to start it. Before I went to start it I noticed the instrument cluster screens were dim and the dome lights were also dim. I should add that I haven't driven the car since Friday (2 days ago), but that isn't enough time to drain the battery anyway. So I turned the key to the on position (position 2) and I checked the battery voltage using the climate control (yes I know it's not the most accurate way of measuring the voltage but it's the easiest). I didn't feel like looking for my multimeter and testing the jumping terminals.

Anyway the climate control showed a voltage of 8.9... I tried starting it but obviously it didn't start. Later on I got a jump, and I continued to monitor the voltage using the climate control as I was driving. I noticed the voltage would stay between 13.3-13.1 when the RPMs were over 1000. Anything under 1000 and the voltage would drop to the low 12's around 11.9 to 12.2. This was with the A/C on, the radio on, and the driver side ventilated seat on the highest setting (3). Eventually I got to my destination about 25 minutes later. When it was time to for me to leave and go back home, about 2 hours later, I went to the car, unlocked it, and started it with no problems. I continued to monitor the voltage on the way home using the climate control again and the voltage stayed between 13.5-13.3 and I never went below 13.3, RPMs didn't make a difference in voltage this time. This was with the radio on and the A/C on.

So after this weird experience I decided I would replace my voltage regulator. The alternator in my car has only been replaced once with a rebuilt unit. This was in 2010 when the car had 77,XXX miles according to my records. The car now has 127,XXX miles so I thought I would try replacing the voltage regulator before the alternator since it's a lot cheaper to do so. I see two Bosch voltage regulators available but I'm not sure which one is the correct one for my car. Links at the bottom for the two that I found.

TL;DR.
I see two Bosch voltage regulators for my car but I'm not sure which one is the correct one. Can someone tell me? Here are the links to the regulators that I see.

http://www.autohausaz.com/search/pr...lectrical & Vacuum&[email protected] Regulator

https://www.fcpeuro.com/products/mercedes-voltage-regulator-1197311242

 

[Kajtek1]

Its been few years since I replaced VR on W210 but at the time all of them were manufactured in ... India !!!
Looks like both links shows the same VR.
Autohousaz will give you free shipping if you build-up the order, FCP did offer lifetime warranty, so weight your options.
BTW I found climatronic voltage display pretty reliable once you figured out 0.5V drop between the battery and computer.
I think this is good time to remind what "rebuild" means.
When different shops take different approach, all that rebuilder guarantee is cleaning, painting, checking for functionality, eventually swap bad part from other "donor" and send back to the seller.

 

[illstplaya]

Yeah the rebuilt alternator was done by the previous owner. So I'm not sure what happened or how it failed.

Regarding the climate control voltage readout, I believe what you say but I know some people in the forum don't really like to consider it a reliable source.

Also are you sure that they are the same? They both have different part numbers. That's what made it confusing. And yes they are made in India. The genuine Mercedes voltage regulator is also made in India so I'm assuming it's the same Bosch regulator just rebranded and more expensive.

 

[Kajtek1]

I think you are comparing suppliers part # what are bogus numbers for me.
Bottom line, both VR are MB OEM parts and good luck making the supplier disclosure where they are made.
What that matter anyway? The Czech -made pilot bushings are better than factory installed.
I would hope VR will follow the trend.

 

[mrboca]

You should be able to determine from the Bosch part number on the unit.

Maybe you can enter the VIN for your car and search for the alternator parts.
https://www.mbwholesalepartsonline....tYW1nJnk9MjAwMiZ0PWJhc2UmZT01LTVsLXY4LWdhcw==

 

[illstplaya]

Thanks for the advice. I'll probably order from FCP since they will allow me to return it with no questions asked. Hopefully I won't have to do that.

 

[Al_Savage]

From your description of events, I would not be suspecting the alternator as the culprit in your dead battery. I am not discouraging replacement of the VR, but do not be unduly surprised if you see the same kinds of results after replacement.

 

[illstplaya]

What do you think it is then? I replaced the battery when I first got the car and that was in October. The old battery was tested and the charging system was tested as well. The battery failed and the charging system passed back then. I did not have them tested yesterday because I didn't have any time for that. I had to go to work.

I already ordered the voltage regulator and it will be here Thursday or Friday at the latest

 

[Kajtek1]

It could be a number of things, but battery taking the charge and holding for a day, while discharging after 2 days would indicate power draw as #1 suspect.
Observe how long it takes for the display to go off after you lock the car?
Still you can't go wrong replacing VR when you don't know the history of old one.

 

[illstplaya]

Yeah I was thinking that as well. But my theory was that the battery probably wasn't being charged correctly on Friday and I was just driving around without knowing it. There were no typical warning signs of low voltage such as diming lights and I never got a red battery message on the instrument cluster. Even on Monday I never got that red warning.

So I figured by Monday the battery just didn't have enough voltage left after not being fully charged on Friday. But this is just my theory. Later on today or tomorrow, whenever it stops raining, I'm going to check with my multimeter to see if there is a significant drain on the battery with the engine off.

 

[nelbur]

When my regulater went bad on my '97 there was a check engine light. If you had no such light, my guess is that the battery was run down somehow.