1999 Sprinter (312D) Ignition/Starting Problems

[MrUBolt]

Hi Fellow Sprinter Punters,
I'm new to forums so please bear with me. My actual vehicle is a Motorhome (only 47500K genuine miles) - 1999 Mercedes Hymer S520, which I believe is model 312D (not absolutely certain). Its a sad story as we've spent pension funds on the purchase and now its looking like we can't use the vehicle due to not being able to fix or replace ignition parts.

The Problem - Intermittent NO CONTACT and failure to turn the starter motor - dash lights are lit and power to radio. On fully turning key dash/ignition light has momentary millisecond flicker, remains lit but there's no contact or start. I've read this could mean overloaded/worn/failing switch contacts, suggesting the switch needs replacing - but that doesn't necessarily help me.

Action so far - Northsidetruck&Van Leeds replaced the ignition cylinder barrel in July 2025 and reprogrammed with 2 x new Transponder keys. It seemed okay initially but I was never 100% confident in the fix as there was the isolated failure which I put down to anomaly, or the way I turned the key. However there is now no doubt the original problem is unresolved (in Nov 2025) : the key/ignition now feels exactly the same as before the Northside intervention and there is a less than 50% probability of a successful start and ignition contact. (The fact the assembly was 'disturbed' and refitted probably accounts for why it functioned with less issue for a short while - but its had extremely little use since July). Northside have washed their hands so to speak (long story there - unbelievably poor service and other damage caused).

Help and Advice Sought:
1. Can anyone confirm the sprinter model details of my 1999 Hymer S520?
2. Has anyone else experienced this issue with ignition failing to contact while power is available to radio etc?
3. Has anyone successfully obtained and changed the electrical ignition switch that mounts on the end of the housing?
(Is the above a push fit clip in plastic switch or is it fixed with bolt/screws and what is the part number?)
4. Has anyone successfully obtained and changed the full ignition assembly i.e. housing including electric switch and ignition barrel with new recoded keys.
5. Can anyone recommend a competent Garage (as near Leeds West Yorks UK as possible please)
6. Where can I obtain parts and how can I be certain they are correct?

PLEASE PLEASE HELP if you can.

Thanks
MrUBolt.

 

[Midwestdrifter]

Being a 1999, it will be the 312D. Which should have the OM602 engine.

I am not super familiar with the electrics on this model (we never got them over here in North America). However it sounds like you have an old fashioned electrical issue.

Basic troubleshooting with test light, multimeter, and probes, will tell you (or a good auto electric tech) if the issue is the ignition switch, starter, starter relay, or an immobilizer issue.


If memory serves, the ignition lock itself is separate from the electrical switch. You can change the ignition switch without modifying the ignition lock or keys. The ignition lock does need removed in order to replace the switch, as they are mounted together.

 

[MrUBolt]

Being a 1999, it will be the 312D. Which should have the OM602 engine.

I am not super familiar with the electrics on this model (we never got them over here in North America). However it sounds like you have an old fashioned electrical issue.

Basic troubleshooting with test light, multimeter, and probes, will tell you (or a good auto electric tech) if the issue is the ignition switch, starter, starter relay, or an immobilizer issue.


If memory serves, the ignition lock itself is separate from the electrical switch. You can change the ignition switch without modifying the ignition lock or keys. The ignition lock does need removed in order to replace the switch, as they are mounted together.

That's really helpful confirmation thanks. As the new key and cylinder don't feel right I'm looking into changing the switch. I will see how that goes and take it from there.

 

[Cheyenne]

Hi MrUBolt and welcome from a fellow Brit,

You can find the full spec of your Sprinter by running your VIN through one of the free VIN look-up sites such as https://www.lastvin.com/

Do you have a manual gearbox or Sprintshift semi-auto box?

And finally do you have a scan tool capable of reading ECU fault codes or Live Data? Actually what diagnostic socket does a 1999 Sprinter have, is it the round 14 pin DLC the same as my 2004?

Keith.

 

[autostaretx]

The "ignition switch" has 3 switches inside itself.
One powers the accessories (such as the radio),
the 2nd powers the engine (it's called the "run" switch),
and the 3rd only causes the starter motor to crank.

If you had a T1N Sprinter, this is what the components at the top of the steering column include:

You only replaced the lock cylinder.
From the sounds of it, you need to replace item (10) in that drawing.
I have no idea if part number A 000 545 81 08 would fit your vehicle.
But this should (hopefully) give you an idea of what part you need.

Item (4) is what's bolted around your steering column (held in place by item (2)).
Item (10) is "merely" pushed into (4) from the bottom, so item (4) may not need to be removed.
In the US, the bolts holding item (2) to item (4) are frequently "one way" or "headless" bolts, requiring cutting/drilling to remove.
I don't know if UK vehicles suffer that technique.

--dick

 

[MrUBolt]

That's really helpful confirmation thanks. As the new key and cylinder don't feel right I'm looking into changing the switch. I will see how that goes and take it from there.

The "ignition switch" has 3 switches inside itself.
One powers the accessories (such as the radio),
the 2nd powers the engine (it's called the "run" switch),
and the 3rd only causes the starter motor to crank.

If you had a T1N Sprinter, this is what the components at the top of the steering column include:
View attachment 389872
You only replaced the lock cylinder.
From the sounds of it, you need to replace item (10) in that drawing.
I have no idea if part number A 000 545 81 08 would fit your vehicle.
But this should (hopefully) give you an idea of what part you need.

Item (4) is what's bolted around your steering column (held in place by item (2)).
Item (10) is "merely" pushed into (4) from the bottom, so item (4) may not need to be removed.
In the US, the bolts holding item (2) to item (4) are frequently "one way" or "headless" bolts, requiring cutting/drilling to remove.
I don't know if UK vehicles suffer that technique.

--dick

Thanks Dick that's really helpful, I'll check the part numbers for a match.
I've attached pics of the steering column. Are you able to tell me how to remove the fuse assembly? I can see the fastenings but I'm unsure what will happen, how to remove and how far it'll detach. I assume I must disconnect battery first.
Thanks
Ged

 

[MrUBolt]

That's really helpful confirmation thanks. As the new key and cylinder don't feel right I'm looking into changing the switch. I will see how that goes and take it from there.

Hi
I've removed the lower steering column shroud (see pics). Do you know how to detach the fuse bank and what 'unfolds' as you do it?

 

[MrUBolt]

Hi MrUBolt and welcome from a fellow Brit,

You can find the full spec of your Sprinter by running your VIN through one of the free VIN look-up sites such as https://www.lastvin.com/

Do you have a manual gearbox or Sprintshift semi-auto box?

And finally do you have a scan tool capable of reading ECU fault codes or Live Data? Actually what diagnostic socket does a 1999 Sprinter have, is it the round 14 pin DLC the same as my 2004?

Keith.

Hi Keith,
Thanks for your pointers. There's no CAN bus so no diagnostics and it's a manual. I'm receiving good help on the forum and working with it.
Very greatful to all.

 

[Cheyenne]

Hi Ged,

I'll try to answer as many of your questions as I can!

Your fuse block on the steering column is similar but not the same as on my 2004 T1N. There is a section in the 2003 Service Manual here

https://diysprinter.co.uk/reference/05%20service%20manual.pdf

which deals with removing and replacing Fuse Block #1 as it is officially called.

You have two relays on the bottom edge of FB #1, are either of these labelled as Engine Control or possibly ECM?EDC ??? If so then try removing and cleaning or maybe replacing it. They are often the cause of trouble on T1N's.

Whilst you do not have CAN bus you almost certainly have K-Line communications and there should be a diagnostic socket, possibly under the very LH end of the dashboard. A T1N is the same with no CAN bus but does have a round 14 pin Data Link Connector immediately below the ECM under the LH end of the dash.



Keith.

 

[autostaretx]

The screw that holds the T1N fuse block in place threads into a nut that is held in the block's plastic.
Something that many many of our T1N members fight is that that nut breaks free of the surrounding plastic and just spins when you try to unscrew the screw.
(there are many older threads about this)
The three approaches are usually: (a) be really gentle when trying to unscrew it. Apply only enough force to unthread the screw without* breaking the plastic. This is very difficult when fighting two decades of accumulated rust on the screw.
(b) if/when it does break free and spin the nut, *some* people have had success spinning the screw with an electric screwdriver (or drill) so that the moving nut actually *melts* the surrounding plastic. Then stop and let it cool completely down. The plastic *may* solidify around the nut in a way that holds it firmly enough to allow the screw to unscrew.
(c) drill it out. (or destroy the fuse block's plastic)

good luck
--dick

 

[MrUBolt]

Hello fellow Sprinter Punters,
Thanks to all for your help, I did manage in the end to get this sorted after the fault worsened considerably, to the point it would virtually not start at all. It turned out to be the solonoid on the starter motor, something which I'd assumed had been ruled out by the first Auto Electrician I engaged, and by Mercedes Northside Trucks in Leeds in their alleged diagnosis. Basically as a result of incompetence and dishonesty and peopole wasting my time, my Hymer has been unusable (safely) for a period of around 9 months.

The moral of the tale is make sure people have done what they claim to have done with certainty before payment. Fortunately I found a good auto electrician in DMB services below....

DMB Services

DMB Services. 429 likes · 75 talking about this. DMB Services offers 8+ years of expert auto electrical work on cars, vans, 4x4s, campervans & light commercials. We provide mobile call-outs for...

www.facebook.com

It is so sad when you can't trust people, but then so refreshing when you find a decent honest tradesperson who delivers a good service like DMB Services. Thanks again to Danial.