BKC glow plug wiring diagram or details

[J.R.]

Sorted!!!

 

Found the in line fuse holders in my celler that I thought I had recovered from somewhere, they are ultra slim profile so one will do the job perfectly.

 

So I will be doing the job exactly as you have, amazing that the photo was actually on the thread!!

 

If only the muppet who installed the electrics had done it right in the first place, he would not even have had to disconnect the battery.

 

The can bus relay module at the back has an LED permanantly lit so a tiny bit more battery drain but nothing like if I leave the shatnav connected as every 168 hours its switches itself back on with the screen illuminated, if I leave the car for more than 2 or 3 days it wont restart, well the old vehicle at least.

 

How much autonomy does a battery have on standby current consumption in a MK2 before it will no longer start the vehicle? More than a 2 week holiday with the car left at an airport parking?

[Norman Willcox]

I mentioned the discussion about the Glowplug controller to my electroniky younger son and he has given me a link that goes into the techniques at some length. You can skip the maths and glean interesting information. Son says that the controller will be a "buck"  or "buck-boost" circuit. See https://en.m.wikipedia.org/wiki/Buck_converter if you have the time!  These techniques are used commonly in computers and mobile phones and more ore less everything else!

[Breezy_Pete]

On ‎04‎/‎11‎/‎2018 at 08:57, Norman Willcox said:

I mentioned the discussion about the Glowplug controller to my electroniky younger son and he has given me a link that goes into the techniques at some length. You can skip the maths and glean interesting information. Son says that the controller will be a "buck"  or "buck-boost" circuit. See https://en.m.wikipedia.org/wiki/Buck_converter if you have the time!  These techniques are used commonly in computers and mobile phones and more ore less everything else!

 

It's a good idea, but my cutdown which arrived this morning says that a PWM approach seems the more likely solution adopted here.  No moving parts like the electromechanical relay I originally thought, before the 6V/5V thing was confirmed.  The little circuit board is potted into the housing, but luckily with a rubbery compound rather than an epoxy, or I'd never have got in.

 

There are four BTS6144P "Smart Highside Power Switch" devices connected to the four glowplug outputs, and the main incoming 12V (wide pin forming a busbar and heatsink for the four devices), and a quick look at the datasheet makes me think that switching these on and off in a variable mark/space ratio will be how it works. This would give an average/effective lower voltage like 5 or 6  or lower, easily and efficiently, with the appropriate adjustments to on/off time ratios.

 

I'll add any more info that comes to light through further excavation of the potting compound.

[Breezy_Pete]

Only thing to add is that it has its own local 'brain' in the form of an ST72254 microcontroller and an 8MHz crystal to keep it in time, hiding under the busbar:

 

Edited 5 November, 2018 by Wino

[Norman Willcox]

Well done Wino. Evidently the ECU will tell this controller what to do and when, having gathered temperature data etc.  I intend doing some measurements when the new plugs arrive; I shall pass on anything that I find.

[SuperbTWM]

On 04/11/2018 at 08:57, Norman Willcox said:

I mentioned the discussion about the Glowplug controller to my electroniky younger son and he has given me a link that goes into the techniques at some length. You can skip the maths and glean interesting information. Son says that the controller will be a "buck"  or "buck-boost" circuit. See https://en.m.wikipedia.org/wiki/Buck_converter if you have the time!  These techniques are used commonly in computers and mobile phones and more ore less everything else!

 

You would know if it was a buck converter from the inductor that would be on the board

 

Good for stabilised DC but for a glow plug circuit a buck converter would be pointless.

 

Good skills @Wino 

Edited 5 November, 2018 by SuperbTWM

[Norman Willcox]

The Bosch glow plugs arrived from Oscaro on Wednesday. I pulled all the connectors off the old plugs and fitted a new plug to No1, in mid air, with a thin wire around the glowplug terminal and down the connector. I attached the oscilloscope probe to the wire and used a croc lead to connect the glowplug body to the negative battery terminal.  Disappointing result! With the ignition on or off, the scope showed absolutely no voltage, and the plug did not glow. A multimeter in No2 connector showed the usual 1.4 volts with ign off and 6 volts with ign on.

So the 6 volts comes through a high impedance and is shorted to earth by the glowplug. This is probably because the ambient temperature was 15.7 degrees C and the ECU knew that no glow was required.

I connected the scope to No2 connector with Ign on, and with the scope on AC, the waveform shown appeared (No plug connected). The amplitude of the pulse is about -0.1V and the intervals are about 0.6, 1.2 and 2.6mS. (1mS/cm) Not very high frequency.  The scope would not sync very well because the waveform was not stable. With the scope on DC, the 6 volts appeared flat - no pulse, no apparent ripple.

I removed the old plugs with no difficulty and fitted the new ones with copperslip. VCDS showed no engine faults after clearing the old faults.

Job done. I know a little more.

Edited 8 November, 2018 by Norman Willcox

[J.R.]

I sold my O scope a few years back, it had languished in my UK garage unused for a decade, it was better that someone actively learning electronics got to use it but I do miss it even though the times I could have used it I was in another country.

[Norman Willcox]

I am very bad at getting rid of tools and equipment despite the rarity of their use; my scope has also laid idle for a very long time. Electronics, much like auto-engineering has advanced and changed so much that the retired professional/amateur is somewhat kept out of the business, and that is also why the scope does not get called for much. Regrets aside, you were probably wise to sell your scope.

[Breezy_Pete]

It's not blindingly obvious to me what's going on from your testing with the scope. Are you proposing that there's some sort of  'glowplug presence' 6 volt sense signal separate from the FETs? It's entirely possible, but those FETs seem to have so much protection according to the datasheet that I don't see why that would be needed? Maybe it's there for diagnostic reasons? I nearly threw out my cutdown this afternoon but stuck it at the back of a drawer instead, Could be revisited tomorrow. 

 

Hoping that you have plans to reconnect the scope when things are chillier to see what happens then?

 

[Norman Willcox]

Hi Wino, I too am clueless as to what is going on. Since I was able to clear the faults shown up by VCDS it must be so that the ECU is content with its sensor input. I do not know if the glowplug connector has 2 wires inside it. There might be a monitor connection - or not. But somehow the ECU learns that there is a satisfactory low resistance at the plug.  I had hoped to detect a mark/space ratio of half; the fact that I did not disproves nothing; it may well be that the output is sufficiently smoothed and actively controlled to be so. Since I did see the 1.4 Volts with ign off, I suppose it is possible that it is this value that the ECU considers to establish the plug condition, but equally it could be the 6 volts presence/absence when the ignition is on (More likely perhaps). The ECU has the opportunity all the time to assess the plug condition because most of the time the plug is not needed to glow. When it is required to glow by low temperature, the ECU does not need to assess, merely to drive the plug.

[Breezy_Pete]

Glad it's not just me that's struggling to understand!

I'm 99.9% sure there's only one wire to each plug, but that doesn't mean that a signal isn't being applied to it (by other connected circuitry) when the FETs are off to do some resistance check or whatever. I scanned the datasheet for any reference to such a signal that might originate from the FETs themselves, but only saw output current sensing which doesn't seem like quite the same thing to me.

If there is such a signal, I might be able to see it in my cutdown despite the absence of all the cut away FETs.

 

Edited 8 November, 2018 by Wino

[SuperbTWM]

2 hours ago, Wino said:

Hoping that you have plans to reconnect the scope when things are chillier to see what happens then?

 

I'm pretty sure I've mentioned a work around for this about 3 times in this thread 

 

Seen as we've got the smellerscope out it seems daft not to force a decent period of glow time so we can figure this thing out, its not like we have anything better to do

 

 

[Breezy_Pete]

No-one's told him where the CTS is yet, I don't think?

[J.R.]

4 hours ago, Norman Willcox said:

I am very bad at getting rid of tools and equipment despite the rarity of their use; my scope has also laid idle for a very long time. Electronics, much like auto-engineering has advanced and changed so much that the retired professional/amateur is somewhat kept out of the business, and that is also why the scope does not get called for much. Regrets aside, you were probably wise to sell your scope.

 

It was the storage environment that was upsetting me as much as the disuse, it had served me well and deserved better, I sold it on ebay and the winning bidder was local, a young guy just finished college and keen to learn so it gave me a warm feeling!

 

There is probably an app for the mobile phone with a small interface box, if there isnt there ought to be.

[SuperbTWM]

14 minutes ago, Wino said:

No-one's told him where the CTS is yet, I don't think?

 

I'm pretty sure its between the tandem pump and battery area. In a small ish coolant line with one of those green plastic clips holding it in.

 

Or it may be in a sort of plastic coolant flange, i'm sure I can picture it in my head but that may have been another type of engine.

 

Either way its around that area, you can't miss it.....if you take the airbox out of the way anyway

Edited 8 November, 2018 by SuperbTWM

[Norman Willcox]

Nope. No help at all Superb. What the L is a tandem pump? Don't bother answering that query - just send a picture. I did remove a couple of sensor plugs and got told off by the ECU and VCDS.

There is a sensor above the radiator in a small tube, and that must be about temperature, but is it the right one?  I have seen no green plastic clips and I can't imagine a "sort of plastic coolant flange".  That sensor after the air filter box is a flow sensor isn't it?

I have a suspicion, given the ever-so-smooth DC voltage seen on the scope, that there may be nothing to observe with the scope attached to the plug controller output leads.

If we are interested in how the plugs are driven, under starting conditions and thereafter, it is probably current that we should be trying to measure; the resistance of the plugs will go up sharply as the element gets very hot and the voltage may probably be controlled lower - but that won't tell us much without knowing the instantaneous resistance.

We already know that 6 volt heavy current can be produced by the controller and that the plug elements will care little whether it is smooth or pulsed. We are unlikely to be able to fathom much about the designers intentions of intensity and timing from voltage measurements, though a scope or multimeter could tell us that the plugs are being fed. 

a+

N

[Breezy_Pete]

Morning Norman.

I'll try to hunt down a photo or diagram of the CTS location this morning if no-one else pops one on.

 

I don't think it's possible for the FETs to produce a smooth 6 volt output, as to do so they would each have to be dissipating the same power as the glow plug they were driving.

There are no large capacitors or anything else that could smooth a 50/50 PWM 12V output, so I expect to find something else in that module that's generating the smooth 6V. It may be something as simple as a potential divider pair of resistors from the ignition 12V feed. That might be applied to the glow plug in order that the microcontroller can then 'see' by how much the voltage is pulled down by the glow plug. This would vary with the resistance/health of the plug.

[Breezy_Pete]

CTS is Item 6 here: https://workshop-manuals.com/skoda/octavia-mk2/drive_unit/1.9/77_kw_tdi_pd_engine/engine_cooling/removing_and_installing_parts_of_the_cooling_system/parts_of_the_cooling_system_fitted_to_engine_(superb_ii_octavia_ii)/summary_of_components_for_engine_with_identification_characters_bkc_bxe/

 

Not sure what access is like.

 

[SuperbTWM]

16 hours ago, Norman Willcox said:

Nope. No help at all Superb. What the L is a tandem pump?

 

Its the vacuum pump & fuel pump driven by the cam on the RHS of the engine. Under it is the coolant flange with the temp sensor in the back of it. see link from @Wino

 

Access isn't brilliant, you probably need to take the pipe off the airbox to get your hand anywhere near so its probably not worth the hassle, but its good to know if you ever need to replace it.

[Norman Willcox]

Hello Wino, thank you for the two posts. I don't argue with your logic. It is a fact that the ECU can establish the condition of the glowplugs when they are not fired up, so something recognises that the high impedance 6 volts has been shorted by the plugs.  The FETs carry the high current when so commanded but it is doubtful that they also provide the supply for the checking function so something else is probably connected to the FET outputs.

Are we sure that the 6 volts is produced within your plug control unit - is the supply definitely 12 volts from the battery/ign.

My engine is a BJB.  The diagram you found is for BKC, BXE. I can't see that Tee piece attached to the short cylinder at that end of my engine. I don't know much about these diesel engines; it looks as though there may be an injection pump (?) located where that temperature sensor is.

There is a castellated short cylinder under this pump with a bunch of leads coming out but it is nothing like your diagram and it is not obvious how the leads might be disconnected - doesn't appear to be a connector there. See pics

Thanks also Superb.  Yes it may be too much trouble and the car is away with the better half just now. I don't suppose VCDS could turn off the sensor, could it?

[Breezy_Pete]

Diagram looks very similar for the BJB, except they've called it item 5 on this one: https://workshop-manuals.com/skoda/octavia-mk2/drive_unit/1.9/77_kw_tdi_pd_engine/engine_cooling/removing_and_installing_parts_of_the_cooling_system/parts_of_the_cooling_system_fitted_to_engine_(superb_ii_octavia_ii)/summary_of_components_for_engine_with_identification_characters_bjb/

 

Somewhere under the convoluted airpipe in your last photo, I guess.

 

I've spent a while digging deeper into the rubbery potting and got the circuit board out from all the overlying stuff, but someone else is monopolising my microscope today so I'm not able to do much circuit figuring. I didn't get a peep out of the outputs by powering up the thing with permanent and ignition 12V equivalents in the appropriate places, though it took a sensible sort of quiescent current, so I guess it doesn't put out the 6V or anything else until the engine ECU tells it to, or else I've broken too much of it getting this far.

44 minutes ago, Norman Willcox said:

Are we sure that the 6 volts is produced within your plug control unit - is the supply definitely 12 volts from the battery/ign.

 

Yes and Yes, I think.

[Norman Willcox]

Found it at last - it might have bitten me! But it is nothing like the bit in the diagram. Trouble is, if I release that green clip and pull the sensor out I shall have coolant peeing out. It is not obvious if there is a connector, or if there is how to release it. (There must be!) I sussed how to release the other connectors last week but this one looks different. When the engine is cooler I shall try squeezing that lever with a pair of pliers.

[Breezy_Pete]

Is that definitely a coolant hose?

I have a vague recollection of the fuel temperature sensor living in a fitting like that?

Edited 9 November, 2018 by Wino

[SuperbTWM]

5 hours ago, Wino said:

Is that definitely a coolant hose?

I have a vague recollection of the fuel temperature sensor living in a fitting like that?

 

That is what I was picturing in my head before you posted the actual location, even got it down to the green clip 

 

I do however fear that this is the fuel temp sensor also, probably on the return/supply leg of the tandem pump maybe? still not 100%

 

It won't hurt to unplug it and see with VCDS which reading you lose/what error code pops up

Edited 9 November, 2018 by SuperbTWM