Anyone experienced in the electronic ignition on The Merc 500 SEC.

It just cut out and stopped and I'm making the assumption its in the 
little box.

I have no spark and when the "black" box was opened it smelt like 
something has been getting hot.  They have a Bosch electronic box.

What I would like to know is how repairable are these things and can you 
buy parts or would anyone have a circuit diagram.


thanks

r

Rob wrote:
> Anyone experienced in the electronic ignition on The Merc 500 SEC.
> 
> It just cut out and stopped and I'm making the assumption its in the 
> little box.
> 
> I have no spark and when the "black" box was opened it smelt like 
> something has been getting hot.  They have a Bosch electronic box.
> 
> What I would like to know is how repairable are these things and can you 
> buy parts or would anyone have a circuit diagram.

There is a very expensive relay under the bonnet on the nearside (IIRC). 
My 500 SEL needed one shortly before I bought it.

-- 
Pete M - OMF#9

BMW 325i SE Touring
Range Rover V8 Turbo

"Wait! We can't stop here, this is Bat Country"

Pete M wrote:
> Rob wrote:
>> Anyone experienced in the electronic ignition on The Merc 500 SEC.
>>
>> It just cut out and stopped and I'm making the assumption its in the 
>> little box.
>>
>> I have no spark and when the "black" box was opened it smelt like 
>> something has been getting hot.  They have a Bosch electronic box.
>>
>> What I would like to know is how repairable are these things and can 
>> you buy parts or would anyone have a circuit diagram.
> 
> There is a very expensive relay under the bonnet on the nearside (IIRC). 
> My 500 SEL needed one shortly before I bought it.
> 

There is a hand full I'll check them out, would make sense if the unit 
was not getting power.

The unit has two connection plugs.

A double wire going to the distributor - and the distributor is pulsing 
so I am making the assumption that is OK.

Then there is another set of 4 wires coming from somewhere else, this 
may go to that relay. Should find a wiring diagram to check for feed 
voltage to the unit.


r

On Mon, 18 Aug 2008 22:00:08 +1000, Rob  wrote:

>Pete M wrote:
>> Rob wrote:
>>> Anyone experienced in the electronic ignition on The Merc 500 SEC.
>>>
>>> It just cut out and stopped and I'm making the assumption its in the 
>>> little box.
>>>
>>> I have no spark and when the "black" box was opened it smelt like 
>>> something has been getting hot.  They have a Bosch electronic box.
>>>
>>> What I would like to know is how repairable are these things and can 
>>> you buy parts or would anyone have a circuit diagram.
>> 
>> There is a very expensive relay under the bonnet on the nearside (IIRC). 
>> My 500 SEL needed one shortly before I bought it.
>> 
>
>There is a hand full I'll check them out, would make sense if the unit 
>was not getting power.
>
>The unit has two connection plugs.
>
>A double wire going to the distributor - and the distributor is pulsing 
>so I am making the assumption that is OK.
>
>Then there is another set of 4 wires coming from somewhere else, this 
>may go to that relay. Should find a wiring diagram to check for feed 
>voltage to the unit.
>
I found a similar problem when I had a 230TE. The ignition system is
such that you can easily be fooled by looking for the fault in the wrong
place. In my case I noticed that the fuel pump mounted under the rear,
which usually runs for a couple of seconds when you turn on the
ignition, wasn't.

I tracked it down to a relay which, on the 230, was behind the battery.
Fortunately it was a dry joint where said relay attaches to the PCB,
which was an easy repair for me. Finding it wasn't though.
-- 
Regards,  Chris    (Please take out my car to reply by plain text email)     
------1967 Riley Elf------1978 Mini 1000------1971 Mini Clubman------
--1972 Mini Clubman estate--1979 Ford Capri--1984 VW Type 25 camper--

On Mon, 18 Aug 2008 20:08:41 +1000, Rob  wrote:

>Anyone experienced in the electronic ignition on The Merc 500 SEC.
>
>It just cut out and stopped and I'm making the assumption its in the 
>little box.
>
>I have no spark and when the "black" box was opened it smelt like 
>something has been getting hot.  They have a Bosch electronic box.
>
>What I would like to know is how repairable are these things and can you 
>buy parts or would anyone have a circuit diagram.
>
>
>thanks
Rob

You could try posting the same question to alt.autos.mercedes where there
are a lot of people who really know Mercedes cars, especially the older
models.

Richard
See http://www.caravanningnow.co.uk where my caravan's for sale.
-- 
Well, they do say that time flies when you're having fun, and to prove
it I notice my sundial has stopped... - Humphrey Lyttelton closing
comment in I'm sorry I haven't a clue.

Chris Bolus wrote:
> On Mon, 18 Aug 2008 22:00:08 +1000, Rob  wrote:
> 
>> Pete M wrote:
>>> Rob wrote:
>>>> Anyone experienced in the electronic ignition on The Merc 500 SEC.
>>>>
>>>> It just cut out and stopped and I'm making the assumption its in the 
>>>> little box.
>>>>
>>>> I have no spark and when the "black" box was opened it smelt like 
>>>> something has been getting hot.  They have a Bosch electronic box.
>>>>
>>>> What I would like to know is how repairable are these things and can 
>>>> you buy parts or would anyone have a circuit diagram.
>>> There is a very expensive relay under the bonnet on the nearside (IIRC). 
>>> My 500 SEL needed one shortly before I bought it.
>>>
>> There is a hand full I'll check them out, would make sense if the unit 
>> was not getting power.
>>
>> The unit has two connection plugs.
>>
>> A double wire going to the distributor - and the distributor is pulsing 
>> so I am making the assumption that is OK.
>>
>> Then there is another set of 4 wires coming from somewhere else, this 
>> may go to that relay. Should find a wiring diagram to check for feed 
>> voltage to the unit.
>>
> I found a similar problem when I had a 230TE. The ignition system is
> such that you can easily be fooled by looking for the fault in the wrong
> place. In my case I noticed that the fuel pump mounted under the rear,
> which usually runs for a couple of seconds when you turn on the
> ignition, wasn't.
> 
> I tracked it down to a relay which, on the 230, was behind the battery.
> Fortunately it was a dry joint where said relay attaches to the PCB,
> which was an easy repair for me. Finding it wasn't though.

I did check for spark and here was none. As for petrol I could smell that.

The control unit, when I took the lid off,  smelt of over heating.

Just don't know hoe one goes about checking electronics.

r

Richard Cole wrote:
> On Mon, 18 Aug 2008 20:08:41 +1000, Rob  wrote:
> 
>> Anyone experienced in the electronic ignition on The Merc 500 SEC.
>>
>> It just cut out and stopped and I'm making the assumption its in the 
>> little box.
>>
>> I have no spark and when the "black" box was opened it smelt like 
>> something has been getting hot.  They have a Bosch electronic box.
>>
>> What I would like to know is how repairable are these things and can you 
>> buy parts or would anyone have a circuit diagram.
>>
>>
>> thanks
> Rob
> 
> You could try posting the same question to alt.autos.mercedes where there
> are a lot of people who really know Mercedes cars, especially the older
> models.
> 
> Richard
> See http://www.caravanningnow.co.uk where my caravan's for sale.

Nothing there someone advertising an auto blog and another money making 
scheme.

Unless it comes up when the whole group has downloaded. Bot very active 
at present.

I've posted it anyway.

Thanks

On Fri, 22 Aug 2008 12:48:29 +1000, Rob  wrote:

>Richard Cole wrote:
>> On Mon, 18 Aug 2008 20:08:41 +1000, Rob  wrote:
>> 
>>> Anyone experienced in the electronic ignition on The Merc 500 SEC.
>>>
>>> It just cut out and stopped and I'm making the assumption its in the 
>>> little box.
>>>
>>> I have no spark and when the "black" box was opened it smelt like 
>>> something has been getting hot.  They have a Bosch electronic box.
>>>
>>> What I would like to know is how repairable are these things and can you 
>>> buy parts or would anyone have a circuit diagram.
>>>
>>>
>>> thanks
>> Rob
>> 
>> You could try posting the same question to alt.autos.mercedes where there
>> are a lot of people who really know Mercedes cars, especially the older
>> models.
>> 
>> Richard
>> See http://www.caravanningnow.co.uk where my caravan's for sale.
>
>Nothing there someone advertising an auto blog and another money making 
>scheme.
>
>Unless it comes up when the whole group has downloaded. Bot very active 
>at present.
>
>I've posted it anyway.
Rob

I typoed, it's alt.auto.mercedes, I didn't realise that .autos. existed
until you mentioned it.

Apologies for the error.

Richard
See http://www.caravanningnow.co.uk where my caravan's for sale.
-- 
He was not going to be found wanting when duty called. He did not
intend to be found at all.  - The Last Continent by Terry Pratchett

Richard Cole wrote:
> On Fri, 22 Aug 2008 12:48:29 +1000, Rob  wrote:
> 
>> Richard Cole wrote:
>>> On Mon, 18 Aug 2008 20:08:41 +1000, Rob  wrote:
>>>
>>>> Anyone experienced in the electronic ignition on The Merc 500 SEC.
>>>>
>>>> It just cut out and stopped and I'm making the assumption its in the 
>>>> little box.
>>>>
>>>> I have no spark and when the "black" box was opened it smelt like 
>>>> something has been getting hot.  They have a Bosch electronic box.
>>>>
>>>> What I would like to know is how repairable are these things and can you 
>>>> buy parts or would anyone have a circuit diagram.
>>>>
>>>>
>>>> thanks
>>> Rob
>>>
>>> You could try posting the same question to alt.autos.mercedes where there
>>> are a lot of people who really know Mercedes cars, especially the older
>>> models.
>>>
>>> Richard
>>> See http://www.caravanningnow.co.uk where my caravan's for sale.
>> Nothing there someone advertising an auto blog and another money making 
>> scheme.
>>
>> Unless it comes up when the whole group has downloaded. Bot very active 
>> at present.
>>
>> I've posted it anyway.
> Rob
> 
> I typoed, it's alt.auto.mercedes, I didn't realise that .autos. existed
> until you mentioned it.
> 
> Apologies for the error.
> 
> Richard
> See http://www.caravanningnow.co.uk where my caravan's for sale.

So thats why there has been no response, have now subscribed to 
alt.auto. and posted again.

That group is actually showing at present 105 unread headers which is 
much better than the other one, at least its active.

Lets see what happens now.

thanks

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Rob  saying
something like:

>The control unit, when I took the lid off,  smelt of over heating.
>
>Just don't know hoe one goes about checking electronics.

Simplest way is to take a known good unit and a multi-meter. Cross-check
resistances on all leads on the good one and make a table then do a
comparison with the suspect unit.
It might not tell you the exact fault (it will if you are familiar with
them) but it identifies a dud one.
-- 

Dave
SE6a