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

sorted

 

you might be alright, I managed to swap the brake servo on my old digifant mk2 without even taking the inlet manifold off. was tight but it did squeeze in

 

The 20v is a bit larger round the back so that could be an issue

 

here you go, I've updated the first post with part numbers as well

028919081, 028919081B or 028919081H - 0.25-0.3bar switch
056919081E or 056919081 - 1.8bar switch

 

start by working out your fusebox pinout using my faq here:
https://clubgti.com/forums/index.php?threads/fusebox-faq.219775/

since the ceramic fusebox cant really take any load what I would do is keep both the fuel and ecu/coil relays separate from the fusebox, just run the old dash sensor wiring, wiper loom, starter etc as before. use inline fuses for the various power circuits, maybe run the lives from the relays to the battery rather than draw any load through the old main live battery wire and fusebox H terminals. If you made a new chunky battery live you would be ok though.

There's an ignition live on the G spades you can use to trigger your relays, or you can re-purpose the old coil power wire if it was on electronic ignition with normal wiring rather than points ignition with the purple/white coil resistance wire. if you get yourself a proper pin tool the fusebox round pins can be found online if you want to remake it all fresh

 

The G spades are all different accessory feeds, only G/3 is suitable for triggering your 20v relays. H spades are all permanent live, these can be used for the live inputs to your relays but liek I say might want to run the relay lives to battery or beef up the original main live to fusebox from the battery.

Dont try to use the factory relay socket for the fuel pump, the output pin is too small and they often burn out on the GTI. VW released a relay relocation kit as a recall to solve the problem.

So you'll want 1 relay to power the ecu and coils, fused with a 15a fuse on the live input, run the ecu permanent live T6/4 to the fuse output also. then another relay for the fuel pump and extra engine power feeds for T6/5, and the 2 feeds for the T14a/5 and 6.

If its a drive by wire loom then there is usually an ecu/coil power relay 428 in a relay box in the engine bay, you can keep this and re-route the T6 live feed over to the battery live with inline fuse, if you have the right terminals the relay box has 3 or 5 spare fuse holders which are perfect for this.

They usually have an SAI 100 relay in the box too, normally you delete it but you can re-purpose this as your fuel relay instead. cut the brown/grey trigger wire from the ecu and splice it to the purple/white fuel relay trigger wire instead. cut the blue/yellow fuel pump power wire and wire that to an ignition live feed. the thick red live run off to battery live, and the thick white/red wire off to the SAI pump split off into 2 or 3 fuses for all of the engine electrics. run a wire back to fusebox and put a spade on it, plug your fuel pump power into it

 

Pjuvis: Pins 2 and 3 are for the speedometer sender yes, if you were using mk2 clocks with mechanical speedometer drive you dont need them any more. however as you have an 02M gearbox there is no mechanical drive inside, you'll have to keep the sender and so wire up these pins. feed the speed sensor output to a mechanical converter box, here's a couple choices:
https://www.dakotadigital.com/index...t_id=886/category_id=287/mode=prod/prd886.htm
http://www.atrol.com/cablex.htm

the blue/white wire on the orange plug is the speed output signal from the cluster to the ECU. On the MK2 this signal is used for cruise control, aktiv speaker system and some ECU. However the signal is only there on GTI clusters with MFA, or some non-GTI which were specified with one of the above options. But since you're wiring up the sensor on the gearbox you can splice the ECU wire to the gearbox sensor output as the signal is the same

 

charcoal canister goes to the bin unless you need it to pass emissions in your country, but the UK its not required the green/white and brown 2 pin near starter wiring is power steering switch, can bin that as well.

Get a 4 pin relay such as a 53 for your ecu & coil power. put a 15a fuse on the live wire to the 30 pin and tap the t6/4 wire into this fuse as well. Run pin 87 to the t6/1 and t14a/8 pins. ignition live to 86, earth to 85.

Fuel relay same deal standard 4 terminal switched relay. Don't fuse the live side instead run 2 fuses from pin 87, 10a for injectors t14a/5 and another 10a for t6/5 maf/carbon canister/lambda and t14a/6 n75 valve. if you're crafty you can re-use the power pin from the carbon canister and run it over to the t14a/6 pin saves you running a separate wire for it. Plus if extra crafty and can de-pin it the pin will swap into the t14a and saves you a splice too. Bit of a pain to get out, need a decent tool and you click the purple secondary lock mech over to release. Then ignition live to pin 86 and ecu purple/white from T6/2 to pin 85.

 

Ok cool keep that then and just add your t14a/6 wire into the same fuse as the t6/5 or splice into the thickest run of wire on that feed. Should still be ok with 10a fuse but can go up to a 15a if need be.

T6/2 goes straight to relay 85 by itself, the 3cu supplies relay earth to trigger relay you see.

G3 will be fine for both, it's under no load. Forgot about fuel pump add a 3rd 10a fuse to the fuel relay and power your pump off it. Or if worried add a 3rd relay for fuel pump and run the live trigger 86 pin to the 87 pin of your fuel relay and earth pin 85