W210 alternator? and SRS light problems. - PeachParts Mercedes-Benz Forum

anghrist · #1 06-13-2012, 11:04 PM

I had the alternator tested at Autozone after replacing the voltage regulator. They gave me a thumbs up saying that its all good.

I put the alternator back in the car 1.5 hrs of frustration later. I cranked the car up and the SRS light is on again. I page through the screens of the CCU diagnostic to screen #24 and I see that the system is only getting 11.8 volts now. What?!?!?

WTcapitalF?

Either the alternator is toast or the charging system is toast somewhere else. I really am about to trade this maintenance pig in on a freaking Honda.

I'm even having to rent a car to keep going to work at this point.

Diesel911 · #2 06-13-2012, 11:35 PM

Even a Honda can have Charging System issues.
But, at the same time I don't see how any one can operate an Old Mercedes as there only Vehicle unless their Work is close enough to walk or bicycle to.

Try unplugging the Glow Plug Relay to see if that is on all of the time and draining the Voltage.
I am not sure on your Alternator but on the w123s it needs a good working Charging Light Bulb in the circuit to give the initial excitation or your Alternator will not charge.

When you first turn the Key on all of your warning lights including the Charging Light should light up; that check the Light Bulbs.

After that there is Ground Cable and Wiring Terminal issues.

anghrist · #3 06-13-2012, 11:53 PM

I do appreciate you input, but I've been through this about six years ago with the alternator.

The frustrating thing was that I tried replacing the voltage regulator this time to save time and money. I should have just replaced the alternator in totality all together from the start.

I was initially getting a low voltage condition of 12.7-12.8 volts where 'normal' is 13.3 to 13.5 volts.

After replacing the voltage regulator, the alternator being the only component that I've touched, the voltage is now 11.7 to 11.8 volts. The voltage will climb to 12.0 to 12.1 when the engine is revved up to 2500 rpm.

I'm just a bit irritated because I had the alternator tested before I reinstalled. I was told that it was good, but clearly, there is less power being supplied to the system now than before.

compress ignite · #4 06-14-2012, 12:17 AM

That Bosch's Alternators will "wear" the "Slip Rings" excessively and they
(the rings) MAY need to be replaced.[Softer Copper Compound???]

Sure enough,when I got my "New to Me" 143 Amp Alt one of the "Slip Rings"
had a Groove that was worn to 2/3 of the thickness of the metal.
In only 65K Miles!!!
So it got: Not only new bearings and a "Cleanup" BUT New Slip Rings" Too.

[Side Note: the differences we see in QC with the Bosch products like
injectors (outsourced to Mianmar) ALSO exist in their Electrical Components.]

Diesel911 · #5 06-14-2012, 01:52 AM

[QUOTE=anghrist;2955316]I do appreciate you input, but I've been through this about six years ago with the alternator.

The frustrating thing was that I tried replacing the voltage regulator this time to save time and money. I should have just replaced the alternator in totality all together from the start.

I was initially getting a low voltage condition of 12.7-12.8 volts where 'normal' is 13.3 to 13.5 volts.

After replacing the voltage regulator, the alternator being the only component that I've touched, the voltage is now 11.7 to 11.8 volts. The voltage will climb to 12.0 to 12.1 when the engine is revved up to 2500 rpm.

I'm just a bit irritated because I had the alternator tested before I reinstalled. I was told that it was good, but clearly, there is less power being supplied to the system now than before.[/QUOTE]

Testing the Alternator on a Test Stand provides good wiring connections; a good Battery source and no Belt issues.

There is also no components that could be running/turned on when they are not supposed to be or short circuits.

It is entirely possible that your Alternator is OK and there is something else wrong.
Even back in the past the big size Auto Analyzers could project a wave form of your Alternator charging. That could show if there was any issues with the Diodes.

Also an Alternator will not work if the previously dead Battery was not recharged.

As a side note I started My Volvo Diesel; drove it and stopped to get something to eat. Got in the Car and nothing happend when I turned the key (Manual Transmission). I had a Volt/Ohm Meter in the Car and the Battery had normal Battery Voltage.
But, when I tried a jumper wire over the Terminals I got only a tiny spark?

I went acrossed the Street and bought a new Battery and the Car started right up. Evidentlay the old Battery had suffered some internal damage to the Plates and while the Voltage was OK there was next to no amperage.
Unexpected causes for things come up once in a while.

cessna5354 · #6 06-14-2012, 03:24 AM

X2 what CI said,

I just had my W210 alt rebuilt and they replaced the ring. The old one was deeply grooved after 271K miles.

I was lucky in that the bearings felt like they were loaded with sand signaling me to rebuild. I am fortunate with a very compentent rebulder checks all wear points, not bearings & paint.

Preserve this alt prob. Keep the W210, it is a great car !!

Good Luck,

anghrist · #7 06-14-2012, 08:38 AM

Quote:

Originally Posted by Diesel911

...Unexpected causes for things come up once in a while.

You are right to suspect things other than the alternator...

however,

-The car does have a new (one year old interstate) battery.
- The car starts and runs, but the charging system voltage is low.
- The feed for the system voltage reading is directly off the alternator and 'feeds' the CAN bus system.
- Even if all of the accessories are on (i.e. lights, blower motor, radio, etc.) a 'healthy' system will still show 13.3 to 13.5 volts, at worst 13.1 volts.
- The alternator is rated at 115 amps which is plenty of amperage for all of the systems on the car (I believe that the older non-turbo cars even used a 90 amp alternator).
- The serpentine belt is, admittedly a bit dry, but still very tight and there are no chirps or squeals, and the tension/idler is very tight as is well.

I'm still thinking that it's the alternator.

anghrist · #8 06-14-2012, 08:39 AM

Quote:

Originally Posted by compress ignite

That Bosch's Alternators will "wear" the "Slip Rings" excessively and they
(the rings) MAY need to be replaced.[Softer Copper Compound???]

Sure enough,when I got my "New to Me" 143 Amp Alt one of the "Slip Rings"
had a Groove that was worn to 2/3 of the thickness of the metal.
In only 65K Miles!!!
So it got: Not only new bearings and a "Cleanup" BUT New Slip Rings" Too.

[Side Note: the differences we see in QC with the Bosch products like
injectors (outsourced to Mianmar) ALSO exist in their Electrical Components.]

Yep, slip rings were a bit worn.

anghrist · #9 06-14-2012, 08:51 AM

Quote:

Originally Posted by cessna5354

X2 what CI said,

I just had my W210 alt rebuilt and they replaced the ring. The old one was deeply grooved after 271K miles.

I was lucky in that the bearings felt like they were loaded with sand signaling me to rebuild. I am fortunate with a very compentent rebulder checks all wear points, not bearings & paint.

Preserve this alt prob. Keep the W210, it is a great car !!

Good Luck,

Yep, just going to replace the alternator. Sending the W210 to the mechanic today so I can work on the W123 instead.

While at the shop I will have them put on:
-new alternator
-new serpentine belt
-new front wheel bearings (they are really kaput)

Hopefully he will be done by noon or so tomorrow. AlldataDIY show a charge rate of 6.2 hours for all the above.

I found another photo of slip rings that are in about the same condition as mine.

anghrist · #10 06-14-2012, 03:11 PM

Okay the SRS light was the issue that spurred this whole hair pulling event. I've learned a more than a couple of things along the way at this point.

1) The alternator voltage is not displayed on the CCU, that is the actual battery voltage 12.6-12.9 volts is normal (not the charging system voltage 13.3 to 13.9 is normal).
2) The Mercedes COMAND system is a wonderful piece of diagnostic equipment if you are lucky enough to have one installed (I do, just saved me at least $400 for a remanned alternator, hold Mute+1+3 for 5 seconds and get codes and system voltage).
3) New Bosch voltage regulator brushes take a few heartbeats to 'bed in' or 'lap in'. Doesn't happen immediately, even though they are shaped.
4) Yes, it is much easier on the W210 to change the voltage regulator with the alternator out of the car.
5) SRS sensors and such are mighty fussy pieces of electrical equipment.

So I started the car and turned on the CCU diagnostics. Screen #24 shows..... 12.8 -12.9 volts, even hopped up to 13.0 volts at a couple of instances.

Turned on the COMAND diagnostics screen and found that the alternator was sending out anywhere from 13.65 to 13.93 volts! Sounds great!

Now what's making that SRS light come on? Time to think... ahah! The light is coming on and the light on the shift panel comes on as well to tell me that the airbag for the passenger seat is disabled. The light comes on when the key is first turned to the glow cycle and then it disappears with the glow light, then reappears with the 'airbag disabled' light This first showed up when I was driving solo, so.....

I move my happy, but still confused, backside over to the passenger's seat. Insert key and turn to glow cycle. All lights on, then SRS, glow and various other lights turn off.... and then.... and then.... the SRS light stays OFF! Viola, the pressure sensor in the seat is getting enough pressure to make it think that a larger person is sitting there. This also works if my petite, and understanding girlfriend is sitting in the passenger seat.

The sensor is smart enough to know when no one is sitting in the seat (i.e. no pressure). There is no one sitting in that seat right now, so why does it think that there is a child sitting there? What could interfere? What's on the seat... sheepskin seat covers? Nah, they've never been an issue in the past. I only took them off to have them dry cleaned. They should be if anything lighter, and they were such a bear to get back on this time because they had shrunk...................

This is what I had though at first. So I removed the seat cover and, no love. The SRS problem persists, must be either the sensor or the cable. I will have to commit to more investigation.

Doesn't explain the fact that I lost steering wheel controls as well, that's what made me think that I might have had voltage issues.

Okay, back to the car. Sit in driver's seat and turn on the key (not the engine). SRS light on-off-on and no steering wheel controls. Oh-kaaaay, Move to the passenger's seat, turn on key SRS light on-off-stays off, and steering wheel controls are back!

So it sounds like either I have a bad seat sensor, a bad cable, or bad connector somewhere in the passenger seat.

anghrist · #11 06-14-2012, 03:18 PM

"
If you receive customer reports in the above model vehicles with the SRS warning lamp illuminated and any of the above DTCs stored, please make note of the fault tracing information shown. To properly diagnose this issue, please follow the SRS fault tree in Star Diagnosis (SDS). This fault tree can be found in a quick test by selecting the stored DTC. If no faults are found, the cause could be a memory card with a transponder chip has been placed on the passenger seat. Company ID cards, notebook computers, PDAs, and other electronic equipment may contain such memory cards that cause interference with the Baby Smart(TM) transponder. This interference can be interpreted as a fault by the SRS control unit. This condition may be difficult to duplicate in the workshop. Please alert the customer not to place items containing memory cards on the passenger seat. Replacement of components will not remedy the situation.
Note: The interference from electronic components is an outside influence and not a manufacturing defect and therefore cannot be claimed under warranty."