Glow Plug Voltage(s)

I have been having problems getting my S3 to start recently, it seems that the plugs are not getting warm enough.

Today I tested the voltage being supplied to each plug in turn (it is original in-series wiring not the updated parallel), the readings I got were:

No.1 6.2v
No.2 4.5v
No.3 1.8v
No4. 0.8v

Now I'm guessing that there will be loss across the in-series wiring but at these readings any plug beyond No.2 will not be getting anywhere near enough juice to warm them.

Does anyone have any advice, I'm expecting that it will be to change the plugs but could I supplement the feed to plugs 3&4 by wiring another lead from the ballast resistor to start at No.3?

fit new plugs they are obviously burning out resistance gettig higher 6 volt okay as they use amps

in this thread:-
http://www.landyzone.co.uk/lz/f6/s3-diesel-glow-plug-wiring-136545.html
You posted a link to the picture attached below.

If that is a photo of your engine you have the new type parallel plugs as the wires are shown clamped together on the second to last plug and the old earth return can be seen hanging free below the pre-heaters. Have you replaced with the older series wired ones?

No that is a different vehicle

Well that wasn't very helpful for answering your previous question was it? Especially as you never came back to the thread to put us right.

Have you had all the wires off and cleaned the connectors and clamping washers to ensure good connection? (That includes the connections on the ballast resistor).
If so and you get no joy replace them as stated above. Remember though if you stick to the old series ones you only need to have one go wrong and none of them will work.

Haynes says 1-7v drawing 38-42 amps, I would expect No 1 at the front would have the lowest volts as no 4 comes straight from end of ballast resistor, it might cock things up jumping a wire to no 3/2?, MHM would know more on this, it would be better to run two series circuits of 2 glow plugs having two earths so voltages should be no lower than 4.5v

OK today the news from Essex..

Removed and cleaned glow plugs number 1 - 3 (number 4 was a challenge and as it started to rain I guessed that as it was the one that had the most volts previously it might be worth leaving it)

I realise that the numbering system I used in my original message was incorrect so my numbering here is corrected (No.1 at the front of the engine now) I found that No.3 had corrosion around ring side of the power IN from No. 4 so this was given extra attention.

Giving power to the plugs after the change (my Girlfriend on the warming switch as I have a separate switch) I picked up higher voltages than previously but after 30 seconds or so I was informed that there was smoke coming from dashboard

We unscrewed the dash and located the source of the smoke, it was from the in-line fuse holder that I had installed between the fuse box and plug heater switch. This was a stock item with a 10Amp blade fuse and rather than blowing it had started to melt not only the fuse but also the in-line rubber fuse holder.

Having read here that the plugs pull 30+ Amps I changed the blade fuse for a 30Amp one and gave it another warm up, hey presto the engine started.

Not sure why the 10Amp blade fuse didn't just blow but instead melted not only the blade fuse but also the rubberised inline holder

[To clear up any confusion from my other recent post about glow plugs, I am asking questions about two different vehicles, one with in-series plugs and one with the updated parallel plugs]

Mine are direct wired from battery +ve to an old type starter button then direct to the plugs. Nice heavy wire, no issues with heat etc. Works a treat.