No start s class w221 - s350 bluetec

Tezmos

New Member
Joined
Oct 18, 2016
Messages
3
Car
S350 blutec
I’m having progressively worsening issues trying to start my s350 - initially when trying to start I noticed that if glow plug light illuminated at ignition position 2 it would start no problem - if it didn’t I used other key and it generally would eventually illuminate glow plug light and start - I fitted a new Bosch agm battery just in case it was the old battery tiring - no real effect from battery change - then I found if I run a tyre compressor from cigarette lighter it would then trigger glow plug light and start - weird but true! - now the only way to get glow plug to illuminate is to put battery charger onto car - battery at 12.54 volts prior to adding charger - with charger on and charging at approx 6A turn ignition on and glow plug comes on and vehicle will start - don’t know if this is a bad earth somewhere or starter motor relay / or starter itself - no clicks noises or anything when trying to start when glow plug does not illuminate - car has done 55k and is in good order - normally!!! - any help or ideas would be much appreciated!🤔
 

Dodipops

Active Member
Joined
Apr 6, 2019
Messages
238
Location
Scotland
Car
C63
Weird? Do you know how to access the service/secret menu?
you will find battery voltage of car in there also the amps drain as well I think.
You should be able to access it with ignition on and then start it to see if there’s a difference.
 
OP
OP
T

Tezmos

New Member
Joined
Oct 18, 2016
Messages
3
Car
S350 blutec
Weird? Do you know how to access the service/secret menu?
you will find battery voltage of car in there also the amps drain as well I think.
You should be able to access it with ignition on and then start it to see if there’s a difference.
No I have no knowledge of how to access the service/ secret menu - please advise!
Noticed today that battery charger had dropped to between 1-2 amps but shot up to 6A charge for opening the drivers door! Started car up briefly and charger then back to 8A charging for quite a while - seems to be some heavy current draw - Battery voltage 13.4 following full charge - 14.4v with engine running dropping to 12.4v following a10 mile run and back home - battery left to settle for 30 mins prior to checking voltage.
 

Dodipops

Active Member
Joined
Apr 6, 2019
Messages
238
Location
Scotland
Car
C63
With ignition on stage 1 and the odometer showing just mileage display (I think?)
Then press and hold call accept and ok on the stg wheel, should get beep and the first thing that shows is battery voltage.

That might not be 100% accurate for your model but if you do a search on here you’ll find it.
 

Aidroos

Active Member
Joined
Jul 13, 2021
Messages
181
Location
Hyderabad
Car
Q7, EQC, S320, Grace, CRV.
I’m having progressively worsening issues trying to start my s350 - initially when trying to start I noticed that if glow plug light illuminated at ignition position 2 it would start no problem - if it didn’t I used other key and it generally would eventually illuminate glow plug light and start - I fitted a new Bosch agm battery just in case it was the old battery tiring - no real effect from battery change - then I found if I run a tyre compressor from cigarette lighter it would then trigger glow plug light and start - weird but true! - now the only way to get glow plug to illuminate is to put battery charger onto car - battery at 12.54 volts prior to adding charger - with charger on and charging at approx 6A turn ignition on and glow plug comes on and vehicle will start - don’t know if this is a bad earth somewhere or starter motor relay / or starter itself - no clicks noises or anything when trying to start when glow plug does not illuminate - car has done 55k and is in good order - normally!!! - any help or ideas would be much appreciated!🤔
Did you fix this?
 
OP
OP
T

Tezmos

New Member
Joined
Oct 18, 2016
Messages
3
Car
S350 blutec
Did you fix this?
I didn’t personally but yes car is now fine!
Whilst I was testing and checking the starter relays it turned out to be a £11 ignition relay - went to a brilliant guy in Hull called Kirk at Auto Elite - after an afternoon of headscratching and updating the ECU and rear SAM turned out to be burnt out contacts inside the ignition relay - Merc and other indies saying it was the EIS or the ISM each an £800ish repair!
So was really pleased to get away in total with a repair costing sub £125 including diagnostic labour and parts. Cannot fault A-E the guy is a wizard - seeing him jet about the online wiring diagram which led him to the faulty relay left me in awe - I don’t class myself as an idiot but the S class electrics are a huge step too far far for my simple brain - you need the right gear which normally entails huge bills - Not with this guy!!
Will use him in future even though I have others on my doorstep!
Hope this helps!
 

Users who are viewing this thread

Top Bottom