2003 A-Class wont start

[mikenco]

Apologies for the delay in replying, but I just noticed this thread on a Google search.

Our little car is fixed!.. After MB said it was definately the starter motor, we bit the bullet and took it to a local garage who only (only!) charged us about £400 to replace the starter.

Since then, it's been absolutely fine. Problem solved.

[cjawahir]

i told you it was the starter , and some one in this thread told you that you can tap on the starter , and this still apply to your vehicle , if you can reach it .

cj

[mikenco]

Originally Posted by cjawahir

i told you it was the starter , and some one in this thread told you that you can tap on the starter , and this still apply to your vehicle , if you can reach it .

cj

Is that an `I told you so?` hahaha..

You did indeed speculate that it might be the starter. But it was not a problem curable by tapping the solenoid. Even if you could tap the solenoid on an a-class, there'd be little point as the engine would have to be hanging half way out of the bottom of the car to even access it.

You do know where the starter is mounted on the engine block, don't you?

Either way, it had to be fixed and no-one was willing to give a 'moneyback guarantee' on their diagnosis.

It was the fact that I could get it replaced 300 pounds cheaper than at MB made the gamble slightly less expensive.

Anyway, job is done and I appreciated all input from the guys on here.

Thank you

[TimS00]

I've read this with interest since I have the same symptoms on my 2001 A160 Elegance ACS (owned from a new-ish demonstrator). My next step is to check the voltage on fuse 8. If I pull fuse 8, then I get the same symptoms (all console lights illuminate correctly, relays & fuel pump can be heard but won't turn over). Having made a measurement this evening (car starting normally), there is +12V on fuse 8 with ignition off, & the voltage falls to close to zero when the ignition is turned to 'start' and 'on' (actually, it's dark now & as I type I'm only 90% certain it was for both start & on).

So I guess from this that the ignition switch is upstream (closer to the battery) than the fuse - correct? And therefore if it fails next time & there is no voltage on the fuse, then this indicates a short in the switch? Does anyone have a wiring schematic of the starter circuit?
Tim.

[lofty]

of course they don't it MB playing the guessing game with only peoples money nothing but a rip off, what they need iis a work shop information system that they can use, of course they have one but just don't bother to use it, and as for diagnostics they way they us it it's a waste of time and costs customer/owners a great deal of hard cash,
The tip is to say if the bits you fit don't cure the proble you refund and remove the part .



the problem with doors locking go to my siteat look it's all there all you have done is reprogrammed the door lock setting while trying to get the car started .
Lofty

And thanks feed back at last.

[mikenco]

QUOTE:
The tip is to say if the bits you fit don't cure the proble you refund and remove the part..


I tried asking that back at the time. MB and the local garage gave the same reply, namely that if the part didn't cure it, then they couldn't (wouldn't?) refund and they'd have to look at something else. Pretty poor form in my book.

I reckon that in the case of the starter for an A-class, even if you could get them to refund the cost of the parts, they wouldn't refund the labour costs as they would have to drop the engine twice (lenghty process). Once to fit the new part, then once again the refit the old part.

My next car is going to be another Triumph Herald. At least I could replace everything on that all by myself from bits purchased second hand

[RichardKC6]

I've got starting issues on an 2001 (post-facelift) A160 automatic - and I think this might be similar. However:

Go to car in the morning - starts 1st time, every time. Absolutely and totally reliable.

Go to car to get back from work - again, starts.

Use the car, switch it off, go to use it again 20 minutes to a couple of hours later - dashboard lights up (ignition is fine), absolutely no sounds from the starter. No attempting to spin, or turn.

My first instinct would be the "park" sensor being faulty, second is immobiliser (but wouldn't the car inform via dashboard if the key wasn't correct? My New Beetle used to flash a picture of the key).

I don't want to waste money chasing up garage diagnosis on this car - it's not worth much money, after all - but jiggling the key makes no difference, I'm pretty sure the ignition switch is fine.

I replaced the battery and the issue certainly went away for a while - but the car does get run for 1/2 hour at least for journeys, so I can't think that it's draining the battery THAT quickly (and indeed, it starts fine). I can't bump start it as it's an automatic.

[mikenco]

Your diagnostics sound exactly like my own (I too queried the ignition switch, alternator and various sensors), although I have a manual gear box, so I had the luxury of being able to bump start.

I also had exactly the same symptoms after replacing the battery (i.e., it fixed it for a while)..

However, I'd be willing to bet that the electronics in your starter motor are failing..

Have you noticed yet that it may be weather sensitive, i.e wet/cold weather, it gets worse?

[TimS00]

Disclaimer: I'm not a vehicle electrician, have not yet tried this, and accept no responsibility.

I'm still waiting for mine to fail again, but when it does, I think it should be possible to determine whether the fault is in the starter motor assembly, or the 'upstream' controlling logic, as follows:
I've located a purple wire which goes via a 3(?) pin connector from the battery compartment through the tunnel bulkhead to the motor. This wire is not close to the main thick loom which runs to the fuse box, but runs direct from the positive battery terminal area to the bulkhead.

If you measure the voltage on the purple wire (relative to battery -ve, obviously), it's zero with the ignition switch off & on, and goes to +12V when you turn the key to the start position (you'll probably need a 3rd hand to make this measurement, or a pair of meter probes that you can clamp on to the wire & battery terminal).

I would guess that next time the car won't turn, then if there is voltage on the wire at 'crank', then the motor assy is at fault. If there is no voltage, then it implies a fault in the lockout relay (for autos & ACS cars), or somewhere else.
My next step would be to turn off ignition, disconnect the 3(?) pin connector on the purple wire (to avoid energising any unknown electronics), and then with a length of wire of about the same thickness as the purple one, to apply 12V direct to the motor-end of the disconnected connector briefly (ignition off), but take care of sparks in the battery well. If the car cranks (obviously it won't start, with the ignition off), then it really supports the 'upstream' theory. If it doesn't crank, then I would guess it really shows it's the motor assembly, or that there are some electronics attached to the motor that I'm unaware of that might be preventing it. Comments?

[The Big J]

Originally Posted by TimS00

Disclaimer: I'm not a vehicle electrician, have not yet tried this, and accept no responsibility.

I'm still waiting for mine to fail again, but when it does, I think it should be possible to determine whether the fault is in the starter motor assembly, or the 'upstream' controlling logic, as follows:
I've located a purple wire which goes via a 3(?) pin connector from the battery compartment through the tunnel bulkhead to the motor. This wire is not close to the main thick loom which runs to the fuse box, but runs direct from the positive battery terminal area to the bulkhead.

If you measure the voltage on the purple wire (relative to battery -ve, obviously), it's zero with the ignition switch off & on, and goes to +12V when you turn the key to the start position (you'll probably need a 3rd hand to make this measurement, or a pair of meter probes that you can clamp on to the wire & battery terminal).

I would guess that next time the car won't turn, then if there is voltage on the wire at 'crank', then the motor assy is at fault. If there is no voltage, then it implies a fault in the lockout relay (for autos & ACS cars), or somewhere else.
My next step would be to turn off ignition, disconnect the 3(?) pin connector on the purple wire (to avoid energising any unknown electronics), and then with a length of wire of about the same thickness as the purple one, to apply 12V direct to the motor-end of the disconnected connector briefly (ignition off), but take care of sparks in the battery well. If the car cranks (obviously it won't start, with the ignition off), then it really supports the 'upstream' theory. If it doesn't crank, then I would guess it really shows it's the motor assembly, or that there are some electronics attached to the motor that I'm unaware of that might be preventing it. Comments?

I spent a bit of time looking through what I have and also my experience as a Merc Mechanic for 15 years and having a car that has this problem, here's my 200cents worth.

You have it sort of right TimS00, But also sort of wrong. On an older starting system, you would have been spot on. You would have to connect your wire downstream from the starter relay for it to work.

Here's how it works:
1. Turn on accessories/ ignition and fuse 8 gets 12v from the accessories circuit and feeds via pink/violet to starter relay.

2. The ECU at the same times tells the engine control relay (although it seems without needing authorisation from immobiliser) to send 12v via pink/red to fuse 2 then via red/blue to the starter relay.

3. The ECU then checks with the immobiliser module via the CAN BUS if it may start. Immobiliser tells ecu all ok/ not ok to start.

4. Turn to start and key switch sends a start signal to the ecu,if ok to start, then the ECU sends a NEGATIVE via brown/red to the starter relay. If not ok, no negative signal sent to starter relay.

5. The negative from the ECU and the +12v from the Engine control relay now meet in the starter relay and activate the electro magnetic coil which turns on the relay, allowing the +12v from fuse 8 pink/violet to pass through to the starter solonoid (hence the massive voltage drop TimS00 mentions when it starts).

6. +12v into starter solonoid via violet/white from starter relay and car starts. When the starter relay has no negative signal from the ecu, a negative is constantly applied to the solonoid via the violet/white which the starter relay connects to when off, via a brown wire on the starter relay's 5th pin, (normally closed) which feeds to the earth location behind the facia on the right hand side.

For Auto transmissions, dont worry about the starter lockout switch. Its in the egs module inside the gearbox. Any fault from that is discovered by the car starting in N but not in P. It uses the can bus to communicate with the ECU, besides, manual cars have the problem too so it's not the switch.

Here's my theory: Starter/ Ignition switch.
When you turn to start, the contacts for accessory let go very briefly, not sending the main start +12v to the starter relay at the same instant the ECU is sending a negative signal to the starter relay. Causing the Immobiliser to think some thing is up like someone is attempting to hot wire it and immobilising by telling the ecu no start for 10 min. In other words, the starting sequence as 1 thru 5 above must happen perfectly within a certain time frame ( Mikenco mentioned the timing elswere in this thread,)or immo says no go.

Fix1 : Take out starter switch and give the contacts a good clean with some sand paper.
Fix2: Im tempted to say fit another relay between the accessories fuse 8 and the starter relay to allow the starter to take its current from the battery directly, or even better still take the fuse 8 pink/ violet wire off accessories and directly to the battery +12v, with a 30a fuse of course. This way when the starter relay turns on, it has plenty instant 12v max amp power from the battery to feed the starter solonoid, and not iffy power being shared with all the accessories.

Why have some people solved the problem by replacing the starter? A new starter wont draw as much current as an older one, so the movement on the contacts in the switch wont create a spark due to the lower current draw. The problem seems to be with cars of the same age, not Milage, rather number of starts. As one can see in the wiring diagram, the current to engage the solonoid, draws directly from the starter switch. The relay only connects it to the starter solonoid. The starter relay is surely made to withstand higher amps so that wont suffer the spark and have stronger contacts. The switch however has far more contacts within and im sure smaller too.

Im going to try my theories out on my car today, not wait till it wont start. Ill still have to give it 10 mins for the immobiliser, so i wont know instantly if it works. Only time will tell. Ill let you know if anything changes.