W245 B Class Electrical Gremlins

[CrazeUK]

Hi All.

I bought my other half a 2009 W245 (B Class Diesel Auto) last year. Unfortunately it was a bit of a rush purchase.

The car on the whole has been fine aside from a intermittent tyre pressure sensor which triggers routinely.
Today she was driving back on her usual 30 minute journey and noticed the SRS light come on, along with dimming of indicators and lights and then the dash started flashing (all whilst the ar is on and running).

When she showed me the car, we noticed the aftermarket car stereo controls stayed lit, as well as the car and mentioned the steering controls stopped working.

FYI: i removed the MMI controller unit from under the glove box a few days ago (maybe it has some baring)

What could this be?
Could it be the Battery? (i remember my old W203 C Class) do this when it had been parked for a few months and the battery was low and not charged fully.

 

[GLK]

Try to pull out fuse 50 - you don't need it anymore anyway.

Let me know, if you want a full fuse assignment from WIS (not the consumer version that's in the fuse box).

 

[CrazeUK]

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[CrazeUK]

Try to pull out fuse 50 - you don't need it anymore anyway.

Let me know, if you want a full fuse assignment from WIS (not the consumer version that's in the fuse box).

Cool.

Thanks mate. Where are the fuses in these things?

Do you think the gremlins are a coincidence with the removal of the MMI?

Oh, she just mentioned, about 3 weeks ago she had the dreaded red battery symbol that came up on the dash for a a day.

 

[GLK]

If the head unit didn't get the shutdown signal, it could've drained the battery ...

 

[GLK]

Cool.

Thanks mate. Where are the fuses in these things?

Under the driver's feet - very easy to access: once you get the floor mat out, you'll see.

Do you think the gremlins are a coincidence with the removal of the MMI?

Hard to say ... depends on how hard you yanked that wiring harness LOL
I would double-check that, everything is still plugged into the head unit as it was before.

Oh, she just mentioned, about 3 weeks ago she had the dreaded red battery symbol that came up on the dash for a a day.

It does sound like a battery problem. I bought a good battery tester a few months ago, can highly recommend it:

FOXWELL BT100 PRO 6V 12V Car Battery Tester For Flooded AGM GEL 100 to 1100CCA 200AH Test Automotive Analyzer Diagnostic Tool-in Battery Measurement Units from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group

 

[GLK]

Fuse assignment for the W245 facelift:

And a pic of the battery & fuse box (it's my A200, but it's exactly the same in W245):

 

[grober]

How old is your battery? Its winter-cold - more electrical loads-heated screens- headlights wipers etc etc etc ---If the battery is more than 3 years old --replace it and get an auto electrician to check the alternator output at the same time. Only after you have checked the two units which power everything on the car should you turn your attention to the electronic gismos. If all the electrics go off in your house you don't start by taking the back off the wide screen TV or rooting around inside your washing machine you go to main fuseboard/circuitbreaker unit.

 

[GLK]

Found a better pic for you:

 

[CrazeUK]

@grober makes sense, I'll go to KwikFit tomorrow. Get them to test it. Will there tests also check the alternator?

@GLK. Your a star machine as always!! I actually didn't know where the battery might be, so would have spent a day scratching my head.

I didn't pull anything hard. Also tested everything after I took it out. Also Mrs didn't moan after, except this afternoon.

I'll remove number 50.

On a side note, I am so sure my old w203 would do really random things when the battery died. Like it did one day in north finchley car park.

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[GLK]

No worries, and I wasn't serious about pulling cables, of course.

BTW, the battery I have, as pictured above, is the [top brand] largest capacity, in biggest physical size, that could fit in the box* - don't be tempted to go 15mm wider, as there won't be any space left for cables, and the breather elbow (just about visible on the right in the last pic). I put a date sticker on it, so I know when I fitted it, a couple of years from now...

I bought it from Tayna - fresh, great price and next day delivery.

* Unless diesel box is larger - not sure?

 

[grober]

@grober makes sense, I'll go to KwikFit tomorrow. Get them to test it. Will there tests also check the alternator?
On a side note, I am so sure my old w203 would do really random things when the battery died. Like it did one day in north finchley car park.
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Fast-fit tyres and battery outlets like Kwikfit have an interest in selling you stuff so their opinion may be biased towards a sale. Your best bet is a specialist vehicle electricial outlet like a local Bosch service centre who should be able to test the alternator output. to date your battery check out GLK's picture of his battery. Just on the lower edge of the battery in the picture you just make out an embossed line of figures and letters [upside down in photo]- the batteries date code should be on there somewhere usually in a week/year type format 4914 but code location and format varies with battery manufacturer- in some its on top of the battery negative post.

 

[CrazeUK]

@GLK. I took out 50 and there was a massive spark and everything went dead!!

Only messing. Re pulling cables, I actually fell for that.

Car started fine this morning. The stereo controls light had been on all night though.

As GLK suggested, I pulled out the 50 fuse for "radio systems" and the SRS light went out. Can't see no further symptoms.

Plan is to get the battery tested anyway.

@gurbor I learnt something new today, the Bosch service centres. Didn't even know they existed. Although I can't find any in Manchester or Hertfordshire. Lol

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[CrazeUK]

Battery tested at STS. Apparently another one of KwikFit brands.

Everything tested fine the guy said.

So I guess, let's see what happens after the fuse removal.

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[GLK]

Good news about the battery.

WhatsApp me you VIN again - I'll check for other options (don't remember seeing them - 537, 865, et al - but just in case).

The fuse was 7.5A, right?

 

[CrazeUK]

Good news about the battery.

WhatsApp me you VIN again - I'll check for other options (don't remember seeing them - 537, 865, et al - but just in case).

The fuse was 7.5A, right?

Cool will do. The PDf didn't work. Said invalid format or something. Yup 7.5A.



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[GLK]

Cool will do. The PDf didn't work. Said invalid format or something. Yup 7.5A.

The pdf attached above didn't open correctly?

That's a first! It is printed in Mercedes WinXP virtual machine (EPC/WIS/ASRA), by CutePDF and normally these have widest compatibility (and all active components - links, etc - are stripped). All the WIS and EPC files I post are produced like that...

I'll send it to you via WhatsApp.

 

[GLK]

Try this:

 

[CrazeUK]

Try this:

This one worked fine. And the WhatsApp.

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[GLK]

This one worked fine. And the WhatsApp.

Cool

Just a brief note, to make it easier to decipher some of the codes in column 3:

Terminal 30 -> direct line from battery's positive terminal (+12V)
Terminal 15 -> switched positive (+12V)
Terminal 15R -> switched positive / ignition on positions 1; 2 and 3 (+12V)