DPF Regen - Install in-cabin indicator light

[MrGreedy]

Rear seats coming out




Wiring running from the boot along the existing loom wiring conduit (you can see the red/black wire and its path indicated by the green colour)

 

[MrGreedy]

Wiring running under the hat tray insulating foam, including cable tie position




LED jointed to the wire and heat shrinked

 

[MrGreedy]

LED installed in the AIRBAG trim clip (this clip just indicates that there is an airbag behind the C-pillar trim, and the clip helps to hold the trim in place. It is NOT connected to the airbag in any physical sense).





SAM in the boot. Green circle shows the black inline 5x20mm fuse holder that I have installed.
The blue circle shows the approximate position of the heated screen power connector, but this is an image of the front of the SAM and the connector is on the back.

 

[MrGreedy]

LED now activates when the rear screen is on.

 

[MrGreedy]

Of course, the real test will be if I've just wasted 6 hours on fitting this only to find the rear screen doesn't heat during a DPF cycle. But at least it has been a very cheap test.

Some thoughts:

I can easily disconnect in the boot, remove the RHS C-pillar trim and cut off the LED and buy a new AIRBAG trim clip if this doesn't work as a DPF notification light.

The LED draws 0.02A at 12v, with an operating range of 9v (dim) to 14v (very bright).

I've gone with a blue LED at 5mm, which is fairly bright at night, but I wanted to be able to see it in the day. One benefit of it being in the location I've chosen is that if it had been too bright (which I don't think it is), then I can just reposition the mirror so I am not looking at that interior portion of the C-pillar trim. I still get full visibility out of the rear screen. 3mm LEDs and different colours (including flashing) are available.

The glass quick blow fuse I have chosen is 0.2A (so 10x the LED power requirement). You might try less.

22 AWG wire is capable of carrying 3A+ (temperature dependent) without overheating - Wiki
I didn't want to go for a much thicker or thinner wire as robustness and ease of handling become more problematic.

I took the opportunity to clean the leather seats whilst they were out, which really allowed a good clean of the non-visible bits that had all sorts of crisps, soft drinks and boiled sweets accumulated down the cracks.
I cleaned all the metal car floor under the seats that you can see in the photo. Again, collections of fragments of boiled sweets, stones, sand, sweet wrappers, 1p, 2x 5p and a 2 Euro coin. Result!

As it was all out in the boot, cleaned out the spare tyre well, all the spare tyre fixing gubbins and the spare wheel itself. Not sure how old the tyre is but it looks like its been used and is probably original. Thinking of getting it replaced (155 70R17 Continental). The cheapest place I've found is F1 Autocentre, and the places that carry this size are limited.

Some of the plastic push rivets that hold the boot trim in look like single use, fail on removal types. I've replaced these with push-centre plastic rivets that can be reused (if you carefully take the centre pin out before removing them, unlike garages who seem to smash them off with an axe and never replace them).

 

[baxlin]

I suggested such a warning light on another car forum I frequent, and the general response was it’s unnecessary on late-ish cars, as ‘interrupted regens’ have been addressed in the software.

Looks like you’ve done a good job here - a pet hate of mine is trailing/visible wires - but placed where it is, won’t it be annoying to any rear seat passenger, who can’t ‘adjust their mirror’?

 

[Tonygw]

Mr Greedy, that is an excellent job..
Be very keen to see how this goes and lights up when the dpf does a regen, as I fancy doing this in mine. Splenedid!

 

[Deleted member 149005]

I thought there was a light on the dash, or on the switch, when the HRW is on?

Or have I completely missed the point?

 

[MrGreedy]

I thought there was a light on the dash, or on the switch, when the HRW is on?

Or have I completely missed the point?

There is a light that activates on the switch itself (centre dash) when the rear screen is turned on via the switch.

However, my hypothesis is that during DPF regen, the heated rear screen and wing mirrors are activated by the ECU, but this does not activate the light on switch on the centre dash.

This is definitely the case for my previous car, Vauxhall Insignia. I have found a couple of posts that have suggested this might also be the case for the S-class.

I tried to look through iCarsoft Pro to see if I could find heated rear screen voltage as a readout, and monitor this whilst driving rather that going through this effort, but alas I couldn't find that live data value with iCarsoft.

Heated wing mirrors also activate automatically when it is not that cold, around 10 degrees Celsius, so quite often and therefore not suitable as a reliable indicator of DPF activity.

Will this work? i.e. does the rear screen activate during DPF regen? I don't know, but I'm driving 200 miles on Saturday, and 200 the next Saturday, so I should pass through a DPF regen. I'll be keeping a live feed of exhaust temperature by using Torque Pro and a Bluetooth OBD2 dongle, so that will show me when a regen is actually happening (650 degrees C during regen, 250-400 degrees during normal diving on the flat/up a hill on the motorway).

The other option is just use Torque Pro, but that means I've got to connect it up every time I use the car and can't use the phone for anything else; namely sat nav.

 

[clk320x]

I respect the perseverance

 

[MrGreedy]

I respect the perseverance

Thanks.

To be honest, I would have rather only written this up IF it works. Not because I fear the incoming bout of additional forum ridicule; but because I nearly couldn't be bothered. At 1am. Having just finished.
The only tipping factor was that I knew for a fact I would have forgotten half of it if I'd left it a couple of weeks and it turns out it does work. And if it does turn out to be useful, I wanted to give back to the forum because I find the forum very useful and helpful and saves me a fortune!

 

[baxlin]

Notwithstanding my comments in post #46 ( which were meant as constructive), I wouldn’t have thought there’d be any ridicule regardless whether it works or not. Certainly not from me, anyway. More like admiration for the effort and willingness to share. I won’t rule out questions though!

 

[Jigglyjohnson]

Hi not sure if this would be possible as the engine control unit access the dog pressure sensor to check the fill level of the dpf and once it hits approx 100% it will check the temp sensors and other engine sensors and initiate a regen
Not to sure how u will be able to monitor this apart from a USB device with engine unit reading capabilities like torque and perhaps link it to a separate phone or tablet which u can leave in the car.

 

[MrGreedy]

I'm not sure is this is possible either, which is why this is an experiment to test my hypothesis on the rear screen, summarised in post #49.

There's plenty of conjecture on this forum that this won't work, but also independent conjecture that this will work. I do know for a fact this works on some other makes and models. I want to see if the same applies for my older 2011 Mercedes (acknowledging newer models might be totally different).

Regarding the DPF regen process, the DPF pressure sensor is used by the ECU to estimate DPF fill (based on manufacturer's data and settings), and a DPF regen is initiated. On older cars say, more than 3 years old, which includes my wife's 2016 TDI golf, the DPF fill percentage is typically 78-80% to initiate the regen. As you get above 85%, the ECU can get quite impatient and might initiate a regen even if the coolant isn't up to full temperature.

In order to burn off DPF soot, additional fuel is sent through the engine, which results in higher DPF temps which can be monitored via OBD2 output with the exhaust temp sensor usually situated just upstream of the DPF body. This is the sensor the ECU uses to predict over fuelling. The DPF regen temp of 625-650 degrees C is not achievable through what I will call normal driving.

Interestingly, for Vauxhall cars and Vag cars there are Android DPF regen OBD2 apps (OPL DPF and VAG DPF) you can download where someone has corresponded DPF pressure and who knows what other sensors to give a live user friendly read out of DPF fill level, temperature, miles since last regen and DPF regen progress when mid-regen.
With my Insignia, if you knew it was doing a regen and were fortunate enough to be at national speed limit, you could put it in gear at 2500 rpm for 70mph and stick on cruise, and regen might clear the DPF to 6% fill. If you accelerate and slow down, keep the revs down even at 70mph, or are in stop start traffic, it might only regen to 30% fill. Plus, the heat generated from regen is significant within the engine bay, so if you have the opportunity to slightly re-route (or safely more quickly slow down to a moderate speed on a long motorway exit ramp to keep moving in anticipation of red lights at the roundabout), it will keep airflow and temps in the engine bay more favourable.

 

[Justintyme]

Thanks.

To be honest, I would have rather only written this up IF it works. Not because I fear the incoming bout of additional forum ridicule; but because I nearly couldn't be bothered. At 1am. Having just finished.
The only tipping factor was that I knew for a fact I would have forgotten half of it if I'd left it a couple of weeks and it turns out it does work. And if it does turn out to be useful, I wanted to give back to the forum because I find the forum very useful and helpful and saves me a fortune!

You are to be complimented on your effort's MrGreedy. Well done.!!!. Very well documented and explained, step by step. And now it only remains to do a "Field Test" and hopefully, it will work. Good Luck with it !!!,

 

[MrGreedy]

Just got back from a good drive. Part way the blue LED I installed came on (no light on the rear heated screen button) and revs were idling at 800ish instead of the normal 600. I stopped only a few minutes after the regen had completed, and the tell-tale smell of a DPF regen was also present.

So, the rear heated screen IS activated during a DPF regen and the notification LED does work.

 

[Justintyme]

Just got back from a good drive. Part way the blue LED I installed came on (no light on the rear heated screen button) and revs were idling at 800ish instead of the normal 600. I stopped only a few minutes after the regen had completed, and the tell-tale smell of a DPF regen was also present.

So, the rear heated screen IS activated during a DPF regen and the notification LED does work.

Congratulations MrGreedy..... Success. . So it can be done. What I was thinking about was something along the lines of a heat sensor fitted to the actual DPF itself. One that would only be triggered in the high tems achieved during a regen, and a LED would light up. I'm not sure about the practicalities of this ( electronics not being my strong point.....) Back in the past, I had a Mini, just a standard one, not a cooper, ( but I was trying to get it to perform like one... ) and I had a 3 gauge set that bolted onto the dash,,really looked the part too !!! One was for oil pressure, another was for amps / charging, and they were all hooked up correctly as it was possible to do so..on the other hand, the 3rd gauge, was for temperature, but no way would it fit into the block, or anywhere else in the water system.....so I just stuck it down by the exhaust manifold. And it worked fine ( did not matter that what it was reading was of no value.. it looked the part !!) It was something like that I was thinking about for a regen notification. But your idea works just fine !! Very strange that the the windscreen element comes live during a regen, but without the notification LED coming on.

 

[Tonygw]

Thats excellent.. The effort has paid off. I am seriously thinking of doing this to mine now. I think we all appreicate your efforst on this forum!

Incidently, whats the tell tale smell of DPF regen? I dont think I have ever noticed any different exhaust gas smells before and I am fairly tuned into strange smells from the car.

Cheers

 

[geoffus]

Just got back from a good drive. Part way the blue LED I installed came on (no light on the rear heated screen button) and revs were idling at 800ish instead of the normal 600. I stopped only a few minutes after the regen had completed, and the tell-tale smell of a DPF regen was also present.

So, the rear heated screen IS activated during a DPF regen and the notification LED does work.

Brilliant, well done, well that’s my next job then.

 

[MrGreedy]

Incidently, whats the tell tale smell of DPF regen? I dont think I have ever noticed any different exhaust gas smells before and I am fairly tuned into strange smells from the car.

If the car has been driven for a good few miles after the regen you won't notice because it should be well cooled and vented by air movement during driving, and it's most noticible if you stop mid-regen, which is something I want to completely avoid, hence the reason I want the LED.

Basically, an acrid, hot, burning diesel, plastic and hot metal smell, caused by the baking of the DPF at 650 degrees C and the baking of your engine bay and associated plastics and rubbers anywhere near the DPF. If you've ever been in a hot steel making plant, something not dis-similar.