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sprinkles08
sprinkles08, ASE Certified Technician
Category: UK Car
Satisfied Customers: 21602
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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, intermittant Fault with electrics, convenience

Customer Question

Customer: Hi ***** *****,
JA: Thanks. Can you give me any more details about your issue?
Customer: intermittant Fault with electrics, convenience message, new main battery, charging at 14.02 volts, aux battery 12.6v.intermittant temp on display 45c, headlights flash on and off.
JA: OK got it. Last thing — JustAnswer charges a fee (generally around $18) to post your type of question to Mercedes Experts (you only pay if satisfied). There are a couple customers ahead of you. Are you willing to wait a bit?
Customer: ok
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Submitted: 11 months ago.
Category: UK Car
Customer: replied 11 months ago.
Mercedes E270 cdi elegance estate reg DK53 EYA
I have an intermittent electrical fault, with a series of fault messages coming up and then clearing them selves. These include Battery protection Conven. Functions Temporarily Unavailable.
Red battery sign.
Service brake fault.
The car runs fine for periods (minutes) then the faults appear then go again, etc.
when the faults starts the following happens,
headlights and side lights either go out or flash on and off with no particular pattern. the interior lights dim and flash as does the dash board ones and the indicated outside temperature goes to 85c.
The battery is new and has 12.6 volts engine off, 14.02volts engine on. All fuses are ok. Aux battery has also 12,6volts.
The previous battery which I thought was not holding charge would go flat if the car was left un-driven for 3 days and as the fault indicated a battery I replaced this but this did not solve the problem.
Car otherwise drives well.
thank you
Andy
Customer: replied 11 months ago.
The problem seems to be worse during wet weather but not sure this is relevant?
Expert:  sprinkles08 replied 11 months ago.

Hello and welcome to JustAnswer!

You're seeing these lights and warnings because charging voltage is low at that time. The most likely cause would be the alternator.

Have you had the charging system tested at the time the battery light is on?

Is the battery still going dead while the vehicle is parked?

Customer: replied 11 months ago.
The battery voltage remains at 14.05, (min 14, max 14.1) throughout when OK and when fault indicated and at all revs.
Their seems to be a drew on the battery when vehicle is parked, battery (main) reduces voltage from 12.6 to 12.2v over 2 days
the front lights completely unpredictable, near side today off completely drivers side flashing like a loose connection on a older car with just a fuse switch and relay.
Andy
Expert:  sprinkles08 replied 11 months ago.

Do you know what fault codes are setting in all modules?

Customer: replied 11 months ago.
not a clue, how can I get these? what modules?
Expert:  sprinkles08 replied 11 months ago.

A scan tool woudl be needed. Do you have a scan tool?

Customer: replied 11 months ago.
no I don't have such a device. would it pick up where an intermittent wire or poor connector was if that was the cause? if so is it an economical to purchase one?
Expert:  sprinkles08 replied 11 months ago.

It wouldn't be economical to buy one just for this and a scan tool doesn't actually diagnose a problem, they're used for reading fault codes and looking at data and electrical testing will need to be done by the person doing the work.

Do you have a generic code reader to at least read codes from the engine controller?

Customer: replied 11 months ago.
The only device I have is a Maxiscan ms309 OBDII/EOBD I bought for my Jaguar long ago?
otherwise its my trusty Fluke!
Expert:  sprinkles08 replied 11 months ago.

That should work to at least see if there are codes stored in the engine controller. Have you used it to see if anything was stored?

Customer: replied 11 months ago.
never used it, Jaguar never went wrong, I connect up in the morning and see, would it work with the Merc?
Expert:  sprinkles08 replied 11 months ago.

Yes, it's a generic OBDII code reader from what I can tell and will work with any vehicle 1996 and later.

Customer: replied 11 months ago.
Hi,
No error codes on OBDII today.
Main battery voltage now 12v
Aux battery 12.6v
Expert:  sprinkles08 replied 11 months ago.

Are you able to see any live data at all on the code reader?

Customer: replied 11 months ago.
there is no data, no fault codes. I think if there was a fault code you can interrogate it further.
Andy
Expert:  sprinkles08 replied 11 months ago.

can you check voltage directly at the alternator when the battery light is on?

Customer: replied 11 months ago.
will do in morning
Andy
Expert:  sprinkles08 replied 11 months ago.

Ok.

Customer: replied 11 months ago.
not so easy, crazy weather and alternator inaccessible. Even with a new fully charged battery the front lights flash on and off and the passengers side sometimes don't come on at all, 3 problems this morning, red battery, service brake, and visit workshop.
Andy
Expert:  sprinkles08 replied 11 months ago.

We either need to check battery voltage at the alternator when the problem is happening or a scan tool is going to be needed to monitor data and see what the ECM and other modules are seeing for battery voltage. Electrical testing is going to need to be done at the time the problem is happening, and there isn't a large chance of diagnosing the problem without a scan tool.

Customer: replied 11 months ago.
will check the voltage at Alternater when the flood water reseeds, weather crazy here.
Andy
Expert:  sprinkles08 replied 11 months ago.

Not a problem.

Customer: replied 11 months ago.
not good news the battery now is flat and im locked out I only have remote, a fully charged battery flat in 2 days of not using.
Is the only way in via putting power to the starter remotely then using remote?
Expert:  sprinkles08 replied 11 months ago.

Do you not have the key blade?

Customer: replied 11 months ago.
doesn't work! seems to be the general thing with MB!
Expert:  sprinkles08 replied 11 months ago.

You're going to need to apply jumper cables or a jumper box to the positive cable at the starter or get in a door using a lockout kit.

Customer: replied 11 months ago.
Ok good old AA man got it open and kindly did some checks.
current draw on battery with car locked everything off is 4Amps!
the current is not going to the Alternator, which he also checked and is OK.
Fault codes are as follows:
P1636 coolant fan control
5150 axel level sensor-rear
9051 load deactivation stage 1
9050 load deactivation stage 2
9040 supply voltage too low
9055 generator faulty
he feels its a BCM?
Expert:  sprinkles08 replied 11 months ago.

How was the alternator ruled out as a possible cause for the draw?

Customer: replied 11 months ago.
The 4 amps was not flowing into the alternator but was flowing out from battery with everything off, the voltage and charging current was correct, 14.15V.
Expert:  sprinkles08 replied 11 months ago.

How was it determined that the alternator was not the cause of the draw?

Customer: replied 11 months ago.
I didn't actually see directly as he was under the car but he was using a clamp around the wires I think.
Expert:  sprinkles08 replied 11 months ago.

I highly doubt that the alternator was actually ruled out. What needs to be done is set up an ammeter and verify the draw is present, disconnect the alternator positive cable and see what the draw does.

You have a fault code for alternator failure in any event and that's going to be related to the charging issue you're having.

Customer: replied 11 months ago.
The fault codes I agree, but I cant understand why the alternator, as the output at 14v is correct even with all lights and electrical loads on and with a relatively flat battery, combined with the fact that 4Amps is being drawn which is not going through the wire to the alternator? I wish it was the alternator, that's a relatively easy and not too expensive! But it seems to charge the battery correctly, the massive current drain when I lock up is going somewhere?
Expert:  sprinkles08 replied 11 months ago.

You have a fault code for alternator failure, that's the reason you're seeing the warnings. The alternator needs to be replaced.

As I mentioned previously they did not test anything to know that the alternator is not the cause of the draw. With an ammeter in place the alternator has to be disconnected to see if the draw changes. If not then fuses would be removed one at a time to see what circuit the draw is on and then components on that circuit can be concentrated on.

Customer: replied 11 months ago.
OK ill change the alternator.
Expert:  sprinkles08 replied 11 months ago.

Good luck with it!

Customer: replied 11 months ago.
Ive now installed a new Alternator and the problem is exactly the same.
Red battery light message
service brake message
Battery protection. Convenience functions temporary unavailableBattery charging well 14.08v
both batteries new.
just £200 worse off
Andy
Expert:  sprinkles08 replied 11 months ago.

Have both batteries been load tested?

Customer: replied 11 months ago.
Both batteries are fine, replaced both and still have the same problem. The capacity of 100AH is correct. lasts for one day at 4 amps. The AA man also checked the batteries, they were spot on.
Also the lights on the passengers side are now not coming on.
Customer: replied 11 months ago.
I also checked all fuses and all those that were live were at 12.76V engine off and 14.08 engine on.
do you know at what point the computer system checks the voltage, because if it is low at that point the failure must be between that point and the power?
Expert:  sprinkles08 replied 11 months ago.

While the battery light is on what is the voltage on the alternator output stud?

Customer: replied 11 months ago.
stud is wired directly wired to rear battery the voltage does not change with the light coming on its always 14.08 /14.10v.
http://bayhas.com/mercedes/w211/contents/electrical/elect_battery.htm
Expert:  sprinkles08 replied 11 months ago.

The alternator is on the right front of the engine. What is the voltage on the output stud of the alternator while the light is on?

Customer: replied 11 months ago.
Ive just replaced the alternator! voltage is 14.07
Expert:  sprinkles08 replied 11 months ago.

I know you replaced the alternator. I'm trying to determine why it's showing an incorrect voltage situation and why.

Can you get a full capability scan tool on it at the time the problem is happening? You're not going to be able to diagnose the problem without the ability to monitor data in all modules at the time the warnings are present.

Customer: replied 11 months ago.
I do not have a scan tool, but the AA chap did a full scan with the following
P1636 coolant fan control
5150 axel level sensor-rear
9051 load deactivation stage 1
9050 load deactivation stage 2
9040 supply voltage too low
9055 generator faulty
He told me the alternator was fine and checked the current flow using clamp around the stud wire.
I have put a new alternator in last night on your advice and nothing has changed, exactly the same symptoms and messages. Even the outside temp being 85c.
Voltage at stud is 14.11v but doesn't change when the fault occurs.
the AA chap said he thought it was a BCM ?
Andy
Customer: replied 11 months ago.
Do you know where this unit is on the Mercedes E270 cdi elegance estate reg DK53 EYA, can I just swop this unit for a new one? is there anyway to check it.
Andy
Expert:  sprinkles08 replied 11 months ago.

I believe they used a code reader rather than a scan tool. Live data needs to be looked at while the problem is happening. I wouldn't expect AAA to have the training or equipment to truly diagnose the issue.

There isn't a body control module, were they referring to the battery control module because of an over or undercharging issue?

Customer: replied 11 months ago.
The equipment they used consisted of 2 units one plugged into the car and transmitted signals back into the van where a computer type unit monitored the car whilst running and just switched on. they cleared the stored data in the car but the same codes came back when engine restarted.
the unit he called BCM could be battery control module it makes some sense, but where is it and can it be swopped out?
Expert:  sprinkles08 replied 11 months ago.

The battery control module is in the trunk and was described on the same page you linked to earlier. Yes, it can be the cause of the problem and it can be replaced.

Customer: replied 11 months ago.
my car is the 7 seater option, it is not obvious where in the back the bcm is, cant see it near the battery? do you know where it is located before I have to strip out the linings.?
Andy
Expert:  sprinkles08 replied 11 months ago.

There is a picture of the location here.

Customer: replied 11 months ago.
this is the location for the saloon mine is not there?
Expert:  sprinkles08 replied 11 months ago.

It may be in the right front strut tower area if you don't see it in the area of the rear battery.

Customer: replied 11 months ago.
right front strut tower area ? where is that?
Expert:  sprinkles08 replied 11 months ago.

Under the hood. Struts are what hold up each corner of the suspension, you're checking the area that the struts mount under the hood. The (vehicle) right rear corner of the engine compartment.

Customer: replied 11 months ago.
thank you will inspect first light!
Expert:  sprinkles08 replied 11 months ago.

You're welcome!

Customer: replied 11 months ago.
Taking a bit longer than I thought to procure a new BCM but should arrive in 2 days.
Andy
Expert:  sprinkles08 replied 11 months ago.

Not a problem.

Customer: replied 11 months ago.
Ok new BCM fitted, exactly the same problem, red battery light and service brake.
so 2 new batteries and new alternator and new BCM.
With every thing off there is a draw on the main battery of 1.8A. this is from the smaller of the 2 wires from the battery, the one going to F33 pre-fuse box. 0.2A goes through F78, 0.7A through F79 and 0.9A through F81.
there is no current flow from the smaller battery or the large positive lead from the main battery.
Expert:  sprinkles08 replied 11 months ago.

The module was new or used?

Customer: replied 11 months ago.
Used but fully tested and functional. Identical problem.
Expert:  sprinkles08 replied 11 months ago.

You saw it functioning in another vehicle?

How are you allowing for timeout when draw testing?

Customer: replied 11 months ago.
After initial draw of 4A approximately it settles to a constant 1.8A and stays at that value for at least 30mins with all doors closed
and gate fooled to be closed.
Expert:  sprinkles08 replied 11 months ago.

How are you doing that?

Customer: replied 11 months ago.
Fluke current clamp