OEM MK4 management wiring => Mk1/2/3 harness install FAQ (Now with added dieselness!)

yep these relays are all wired with live to 30, output from 87, live trigger to 86 and earth trigger to 85. ECU/Coil relay needs ignition live trigger with fixed earth so it comes on with ignition. fuel relay has switched earth trigger from ecu and ignition live so it can be triggered with ignition on but only when ecu tells it to. secondary fuel relay if you add one would then be switched on by the ecu triggered fuel relay

Most relay will have an amp rating, usually the 4 terminal switched ones are 40a which would be fine for you as you're going to have a 10 or 15a for the t6/5 and t14a/6, 10a from t14a/5 and a 10a for your fuel pump

if you went for a 67/80/167 fuel relay from a mk2/3 then you'll need a different relay holder as they use larger terminals for the 30 and 87 pins, I've put part numbers in the first post for them anyway.

 

can fuse the extra fuel relay either on live or output pin makes no difference if you only have 1 feed on it

can use normal or big terminal relays its up to you, the larger terminal relay would be better if you were running all 3 fuses to a single relay but as you're splitting you can use smaller terminal i.e. 53 relay if you like. or big terminal for all 3, whatever works for you

match the wire gauge to the output feeds you're using, t6/5 is 2.5mm2 so make sure the fuse input is the same. ecu/coil power & fuel, pump use 1.5mm2, injectors 1mm2

 

whichever works best but ideally you should only have max of 2 wires per crimp. so you could have 1 thick wire from relay and daisy chain to the other 2 fuses, or have 2 wires from relay for 2 fuses and daisy chain last fuse off one of them. the wire which feeds the daisy chain fuse will need to be a bit thicker though as its feeding several fuses if you get me.

I would probably run the 15a fuse to the relay direct, then run another wire from relay to feed the 10a fuses.

the original wire gauge is 6mm2, you could go up a size say 8mm2, or you could run a separate wire for your relays direct to the battery if you like whatever you have to hand which will work for you basically. Can use any H terminal, pick one of the big ones

 

the glow plug relay can go now obviously, pin 50 will be a trigger feed to the relay which you dont need. for the conversion you just need a wire from ignition switch pin 50 direct to the starter, from memory theres a spade terminal connection in the dash loom can take the mk4 starter wire and join it to that job done.

G/3 is the only one which is ignition live, you can tap into the existing wire for the relays as I say theres no load on this feed its just to switch the relay. but if worried you can tap into pin C/15 which would be for the coil originally, or A/12 which is usually empty, or A15 which feeds various engine electrics such as reverse switch. you'll need a multimate pin if the pin location is empty.

or can move the radio tap to the blower motor black/red wire, of if your ignition switch has the SU pin on it feed it here this is where later MK2/.3/4 radios are powered from, nbeed a 2.8mm latched spade then the radio will switch on as soon as you insert the key

 

ecu relay is a 109 seperate from the fusebox in a PD golf, if you look at my guide carefully this powers T6 brown pin 4 & 5 and some also pin 6 plus T10a or 14a pin 6. The ECU relay trigger comes from T10h blue plug pin 8. So to wire up your 109 relay:
30 - good chunky permanent live feed
85 - T10h/8
87 - t6/4 with 30a fuse, T6/5 & t10a or t14a pin 6 from a 10a fuse.

If its there t6/6 feeds crank case breather heater and coolant glowplug relays, this can be tapped into the fuse for t6/5 just bump it up to a 15a for the slight extra load from the heater if its there. if no heater then can keep the fuse 10a as the coolant heater relays only use it as a trigger. if not using the coolant heater either then this wire can be stripped out entirely

for glowplug/fuel relays you make a choice. either wire fuel pump as per petrol mk3 and use a petrol rear wiring loom to power the diesel fuel pump, or run a fuel relay seperate from fusebox and instead use the mk3 glowplug relay wiring setup. if you use fuel relay on fusebox then run the fuel pump trigger to G1/3 and run fuel pump wiring to M/1 and 2 same as a petrol mk3. if you want glowplug relay in fusebox like a mk3 diesel then run the glowplug relay trigger to G1/3 and PD glowplug wires to Z/1 with suitable inline fuse

 

the S3 uses a simple turbo timer relay for this, plenty available aftermarket

 

the main one you need is the blue wire for the charge light, 2nd pin is DFM which later ecu use to moniotor the alternator. dont think its really needed but as I re-wire the blue battery light to suit mk4 alternator loom I do the dfm pin while im there as its no extra effort

 

hello there. so what you need to do is add the oil switch(es) from the old engine to keep your clocks happy. older VW only have the one oil switch so if you only had 1 switch on your engine then the 0.25/0.3bar is all you need. later models also had the 1.8 bar switch, without that the clocks will buzz and flash over 2k rpm

 

pretty much yeah you just need the powers and earths to get it going. ideally wire ecu to trigger its own fuel relay plus the ecu/coil power if drive by wire. you need to wire up the altenrator blue wire otherwise it wont charge, and you need the vehicle speed signal also but you can wire this to the sender on the gearbox if going with electronic cluster. you want the clutch switch to stop revs hanging between gear changes and if you want launch control brake switch too. plus diagnostics port is always handy