The glowplugs run on 6v, sounds like your old school faultfinding reactions are just like mine were, wanting to check everyything rather than just obey people that simply say "change all the glowplugs", in my case I did not think that they would all have had failed and it must be a relay/wiring/fuse problem.

 

I was 100% wrong, 4 new Bosch glowplugs which cost next to nothing removed all the fault codes and now in the cold weather the engine starts before it has even turned 180° and had time for the cranking to slow down as all cylinders get compression.

 

I also use VCDS as my first diagnostic tool and then consider what it tells me against what I know from my old school fault finding logic.

 

I never changed the glowplugs in 16 years and 325000 miles on my MK1 Octavia, either they were longer lasting or the engine did not really need them and the ECU did not monitor them to throw up fault codes, if it was the latter then I wasted a lot of time over the years waiting for the glowplug light to extinguish before starting the engine.

Thanks for your response J.R.. I had a dual mass flywheel explode and damaged the housing and the gearbox. Being away in UK had to have a garage sort it. Chap said that the old engine was b**gered because the timing belt had jumped and pistons had hit valves. Had to believe him. He put in a used engine, said to have done only 100km. I don't know the history.  It seems OK but I  do get a horrible pre-ignition bang on starting sometimes. I am hoping that new glow plugs might alleviate this - but maybe they will make it worse!  I found a Utube video of testing glow plugs - chap was connecting 12V to them direct from the battery. They took ages to glow, maybe half a minute. Seems to me that if the ignition is turned straight  to start, having glow plugs is a waste of time.  My icon goes off inside a second - plugs disconnected.

I was testing the voltage with a digital multimeter, open circuit - no load, so the reduction to 6V cannot be achieved by resistance; that suggests that a high power solid-state voltage regulator is employed! Fancy that! Would it not be cheaper to use 12V plugs? I tried to change a glowplug on a Rover TDi some years ago and it broke. Carried on using the car with a duff GP. So I am somewhat nervous about the coming change. Years ago it was suggested to use penetrating oil before trying to unscrew them - can't believe that the oil will penetrate a seized thread. Think Skoda uses copperslip on assembly?

Incidentally there was a small voltage, 1.4V, showing on the multimeter before the ignition was switched on - puzzling; I don't know how the ECU could know the condition of all 4 plugs, given the apparent lack of a sensing wire.  Does the loom carry individual wires for each GP? Are there 4 voltage regulators?

On my engine there is an individual pair of wires to each glowplug and the ECU senses the volt drop, the fault code is quite simple and will be the same for a high resistance one or open circuit, 3 of mine were dead, one high resistance, so regular scans with VCDS will show up failing plugs before they stop working.

 

Yes 6v surprised me also but when you think about it the glowplug and cranking load will drop the battery voltage to say 10v, using a regulated 6v to the glowplugs means they will always give their all.

 

I too was worried about removing mine but they came out just fine, just as well as I am losing my feel for when fasteners shear or yield.

I'm sure the glow plugs are 12V, if you measure them when they are being called for i'm 99.9% sure you will see the battery voltage.

 

I can't think of any reason why you would run 6v to any of the glow plugs, this could just be the voltage that is being used to see if the plug are good or not.

 

I have been wrong before though....

 

Best way to test is unplug CTS which gives maximum glow time for the plugs, this will give you chance to test them.

 

Edited 1 November, 20187 yr by SuperbTWM

Good thought J.R.

Thank you SuperbTWM. I am in France. I buy parts from Oscaro on line. Here is the description of an NGK glow plug for my engine. You can see that they mention "Tension 5V"  that means "Voltage 5V". It would be nice to hear other opinions on this question.  If the 6 volt supply is real, then there must be a replaceable part which does the conversion - someone must know if it is so!

Where is this CTS? I must find it. Think it is mentioned in the thread above; I shall look.

 

 

Taille de clé à bougie : 10 mm

Code moteur : BJB, BKC

Version de bougie de préchauffage : Bougie de préchauffage métallique

Longueur globale : 101 mm

Gamme : D-Power

Résistance : 0,4 ohm

Filetage : M10 x 1,0

Ampérage [A] : 10 A

Tension : 5 V

Type de raccord : PIN

Profondeur de position : 30 mm

21 hours ago, Norman Willcox said:

There is a relay there marked 100. I removed the relay and tested it on the bench - it works. With it removed the icon does not appear when the ignition is switched on. A good clue that this IS the glowplug relay

 

I don't think that reasoning is necessarily right.  That relay could be powering a number of things that might result in the glowplugs being disabled, like the engine ECU.

 

First things first, what year is your car and what is the engine code?

 

How many pins does that relay 100 have? The Glowplug control unit has 9 or 10 for the BKC engine that JR has.

 

As far as I can see, this is what the glowplug control unit looks like:

https://www.ebay.co.uk/itm/Mk5-Golf-2-0-TDi-Glow-Plug-Relay-03G-907-282-A-03G907282A-Beru/153149397878?epid=1925273481&hash=item23a86a5b76:g:IQMAAOSw1xVa~FPx:rk:11:pf:0

 

 

Edited 2 November, 20187 yr by Wino

Thank you Wino. You may be right. I have no definitive proof that the relay shown in the picture is solely for the glowplugs. It has 4 contacts, 2 large for the current and 2 small for the coil. Its size suggests that it might not be capable of carrying the high glowplug current(s) [up to 120 Amps?] but if it is just commanding a glowplug control unit - no problem. My car is 2006 and has a BJB engine.

Where is JR's control unit mounted?  I need to find where the CTS temperature sensor is also.

I saw a Utube long explanation of the glowplug relay circuit yesterday; I will try to find it again.

Musing now: There seem to be different requirements for the glowplug operations. For starting from cold a fast heat-up is obviously beneficial, the keeping hot later to assist engine warm-up time might suggest less heat and drive voltage. Since my test was done in ambient temperature of around 15 degrees C, the ECU would presumably not be asking for fast heat; maybe the 6 volts is good for the keeping hot regime. (But the NGK plug does specify 5 volts!)

11 hours ago, SuperbTWM said:

I'm sure the glow plugs are 12V, if you measure them when they are being called for i'm 99.9% sure you will see the battery voltage.

 

I can't think of any reason why you would run 6v to any of the glow plugs, this could just be the voltage that is being used to see if the plug are good or not.

 

I have been wrong before though....

 

 

And in the nicest possible way, you are wrong agin this time!

 

I have given an explanation of why the glowplugs are run at 6v (I think it might be 7v) rather than battery voltage, its the same reason that all the control modules will have 5v logic circuits.

 

Norman you are doing exactly what I was doing, probably for the same reasons thinking it implausible that all 4 plugs will have failed or be outside of limits yet the vehicle behaves normally, you will see I got some very direct "change them" replies which I initially dismissed (its easy to trot that out without any analysis) but they turned out to be 100% correct, seeing how they had degraded to various degrees with 2 completely failed I now realise that unlike my previous 1.9 tdi these have a finite life, if I bought another vehicle I would swop them as a preventative measure or regularly do a VCDS scan, I reckon like me if you change them the codes will erase and stay erased and you can turn your attention to other real rather than percieved faults.

 

I would strongly advise you to not use Oscaro, do some Google.fr'ing and you will see all the reaons why, I know of 3 people having to take them to court. Also the listing is for pattern parts (editted, I see they are NGK), my original Bosch glowplugs were made in France but the cheapest seller including delivery was on Ebay UK, - plus ça change.................

 

https://www.ebay.co.uk/itm/X4-Bosch-0250402005-GLP050-Glow-Plugs-For-VW-Caddy-Golf-MK-V-Passat-Touran/263353889803?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

 

Edited 2 November, 20187 yr by J.R.

My impression of the glowplug control unit is that it's just a high power relay with one very chunky 12V input pin, and four smaller output pins, an ignition 12V supply, a ground connection and two connections to the engine ECU which presumably command and monitor the outputs' status. 

I've yet to find a picture of the innards online. Still looking.

 

@Norman Willcox your BJB appears to use the same glowplug control unit as JR's according to here (second item 17) https://skoda.7zap.com/en/cz/octavia/oct/2006-419/9/937-937020/

 

The wiring appears to be the same, as does the location description 'below the E-box'.

 

Not sure where the CTS is.

 

Edited 2 November, 20187 yr by Wino

I have ordered Bosch glowplugs from Oscaro. I am convinced of the need to change them after measuring their resistances. Now I am just interested to know all there is to know about the control circuit. and where it is.

In the old days, pre ECU there was indeed just a gutty power relay. Now it seems that finer control is available from the ECU and that has been made use of. The 6 volts that I and JR have measured proves that the control unit is capable of reducing the 12 volts battery supply - how much more it is capable of remains to be found out!

I have had a good experience with Oscaro over, I suppose 15 years.  I had a little toing and froing about getting the refund for returned brake cylinders but they paid up after I nagged. Other than that they have delivered the right parts quickly every time for me.

I'm just in the process of buying a cheap secondhand control unit off ebay, so I'll know more about the innards next week.

A spec I saw somewhere this morning suggested that less than 1 Ohm is the criterion for a good glowplug on these engines.

The NGK spec says 0.4 Ohms

That little simple relay (like my "100" one) is nothing like JR's Ebay link shows.

 Have I really got to take out my battery to look under the fuse box?

4 minutes ago, Norman Willcox said:

Have I really got to take out my battery to look under the fuse box?

 

Don't know, will carry on researching that, but the ebox is the thing your 100 relay is plugged into, so I'd expect the glowplug control unit to be 'below that', as opposed to beneath the battery?

Looks like this may well involve battery removal, but this vid makes the rest look easyish.  Why not just change the glowplugs and watch the problem go away?

 

Edited 2 November, 20187 yr by Wino

1 hour ago, Norman Willcox said:

I have had a good experience with Oscaro over, I suppose 15 years.  I had a little toing and froing about getting the refund for returned brake cylinders but they paid up after I nagged. Other than that they have delivered the right parts quickly every time for me.

Too late now but if you read the French media you will see an altogether different picture this year since they were sued by several suppliers for non payment.

 

The link I gave should have been for glowplugs not the relay.

 

Once my problem went away with the new plugs I gave up my quest to find the elusive relay and control module, there are plenty of other things to occupy my headspace like where the canbus relay unit is fitted for my non functioning towing electrics, what are the 2 blade fuses for that I found behind the NS rear light that look factory but have several black wires leading off to where I think the non functioning canbus relays are if they were even ever fitted.

3 hours ago, Wino said:

My impression of the glowplug control unit is that it's just a high power relay with one very chunky 12V input pin, and four smaller output pins, an ignition 12V supply, a ground connection and two connections to the engine ECU which presumably command and monitor the outputs' status. 

I've yet to find a picture of the innards online. Still looking.

 

 

I can only go off the last time I tested a glow plug harness and that was a pd130 AWX. 

 

If it had had been a 6v output I would have remembered so I’m 99.9% sure it was 12v. Only thing I can think of is that some engines use PWM control to vary the output of the plug making voltages appear lower

 

I do have a BKC engines golf I can test if I get time this weekend

That is probably how they achieve it, it makes the jump lead testing regime seen so often on Youtube very suspect, makes a good video image but no reflection of what actually goes on in the engine and may well foreshorten the life of an otherwise good 6v glowplug

Useful video showing removal of the glowplug controller.

I have rechecked the open circuit glowplug voltage. It is 1.4V, ignition off and 6V, ignition on; when the ignition is switched off again, the 6V remains for 45 seconds, going off with an audible click. (Now the reason for delay that is puzzling - cleaning purpose?) When the ignition off initial voltage is measured with an old fashioned analogue Avo8 it is 0.1Volt as one would expect if flat batteries were not wanted. The constant low voltage is therefore at high impedance and would not show when connected to a good glowplug.

I don't know where the relevant ambient temperature sensor is situated. I disconnected 3 likely looking sensors and none made any difference to the 6V - from which nothing can be gained!  

That is more than enough for the moment; I await, with bated breath, for the arrival of the new plugs. I shall test them before I fit them, and try to measure the supply connected to a live plug.

Would a digital multimeter show 6V for a 12V even spaced PWM supply? And no I am not going to attach the oscilloscope just now, but I might when the plugs arrive.

Found something interesting that explains the confusion.

 

The AWX 1.9 PD engines uses 12V glow plugs.

 

Obviously the 105 BKC PD being a newer design must have that clever box of tricks and are using 5V glow plugs. 

 

I knew I wasn't going mad when I had measured 12V on the glowplug harness 

 

 

 

 

Edited 2 November, 20187 yr by SuperbTWM

As the discussion has already deviated towards accessing components on the battery fuse board and there seems to be some knowledge from the contributors I will ask this question here before creating another thread.

 

I have been faultfinding why my trailer wiring was not working, lack of a 12v feed to the trailer lighting relay and auxiliary power modules, I had myself removed a very dodgy looking open eyelet connector to the main battery terminal until I knew what it was, now I know and its just as well I removed it because the downstream wiring connections were appalling as sadly I usually expect of towbar or radio electrical work.

 

I want to reconnect it in a safe and proper manner and not see a loose cable dangling, it makes perfect sense for me to connect to one of the unused fuse holders in the fuse plate from underneath.

 

My question is can the top part with the fuses and relay be seperated from the lower part to gain access? There are 3 very small Torx head screws and one much larger one centrally.

 

Many thanks.

J.R. I am not sure if this is relevant for you. My Octavia did not come with a tow bar etc.. I fitted my own and bought a relay thingy from Ebay. It does not upset the Canbus and used to bleep correctly with the indicators until I changed the trailer board to LED lights. Now it bleeps intermittently and stops when the brake lights illuminate. I needed to have a battery connection in the boot so I fitted an in-line fuse and attached it to one of the spare live terminals hidden under the battery fuse box lid, at the front. You can see this in the photo I attached many posts ago. (The picture is at the bottom of the 1st page above). You can see the fuse connected to the 5th stud from the left.

Very relevant and that is precisely where I was going to fit it but the in line fuse holder looked too big to fit in the sapce where yours appears to be, and then I dropped it down the back of the fuse board so now its lost for ever.

 

Yours looks like a much lower profile one so I will try and find one, I have a nagging feeling that I have some already hidden away somewhere.

 

Mine needs a 40 amp fuse right by the take off point and it has two 20 amp ones at the back feeding the modules.

 

Do you have any trouble removing and refitting the fuse box cover?

 

The abortion that the guy made of mine meant that the side pieces of the battery cover were all seperated and the top cover did not fit, all sorted after I removed the errant cable.

 

Its scary that somewhere eles in the universe there is someone having exactly the same thought processes as me and doing the same things!