This question may be small and insignificant but no where seems to describe what the pin are on these late alternators. So I have created an illustration that should make it clearer. Pin 2 is the blue exciter wire that is an input from the cluster LED light. Pin 1 can sometimes have a brown/red wire, which is used by the ECU to monitor alternator torque and speed. Hope this helps
Excellent, thanks very much!!! Andy, on your Andyout loom did you use the 24v ecu wire and the original Mk2 blue exciter? I want to do at least 1 R32 powered Curby THIS year lol
Ian, you only need the blue wire for the Mk2. Hopefully the 0.5mm blue wire in the engine bay should still be connected back to the cluster.
I have built my loom to use both wires. Not difficult to wire both in..... Note, the VR engines call the terminals DFM and L, not W and D+
I am aware, although the schematic in the illustration from from a BDE 2.8 24v engine *Edit* DFM is digital field monitoring and L is lamp.
Thanks guys Is there a benefit to having the ecu one connected? I'll trace the wire in the 24v loom back and see where it goes. I think it must be the ecu one but will check.
I thought the M of DFM was monitor, rather than management? Possible benefit of connecting it therefore could be that the ECU knows how much electrical load is on the alternator, and can make alterations to fuelling/timing/whatever to compensate, e.g. to achieve steady idle speed, or increase it if required to maintain system voltage. ??
Edited the my post on your correction. Some 1.8Ts also have this feature utilised was well. What you said sounds sensible for a car with many electrical consumers. However the changes to maintain some sort of torque reserve at light loads will be very small and do not affect driveability. Certainly not on a MK2 Golf.
Yeah info on if the DFM pin actually makes a difference either way is sketchy, if you want to run it on your mk2 you may find the wiring is slightly easier if you use the MK3 pin for the exciter wire on F/3, that way the blue wire and ecu pin can be on the same run with engine loom rather than having to have a plug somewhere on the dfm or exciter wire so the engine and lighting looms can be split later if need be
Assuming this is one of your looms, would not the "DFM" wire at the alternator, be connected to the ECU at pin 28 already? Therefore leaving only the excitor fly lead to locate the original MK2s blue wire somewhere at the battery? Ian to the 2 wires DFM/W and L/D+ already have the jack for the alternator? Or just two flyleads?
on the mk4 loom the DFM wire goes back to the fusebox coloured loom plugs, then the wire from there runs back out via the main engine harness to the 2/4 pin plug where the alternator wiring plugs in along with the dash excitor and the aircon wires if fitted (this is why diagrams show it on both a 2 and 4 pin, 2 pin for non-ac, 4 pin for ac) with the mk2 wire in the lighting loom its slightly more awkward as you have a plug to join alt loom to main loom, and you'll need a wire to this from light loom and engine loom so another plug is needed on one of them so in future the lighting and engine looms can be split. If you bin the mk2 wire and instead use the MK3 position on F/3 this removes the need for the extra connection
The 2 wires from the alternator run along inside a shield with the big wire to the starter, there is a plug at the end where the sheiks/sheath/cover ends. Will get a new multimeter and have a good look tonight
