car not starting and no engine lights !!

[ds2601]

This week I had some problems with my Golf, it started last Sunday I was driving back from Preston to St Albans  , I had got as far as the last services on the m6 before the m1 and stopped for a pee stop, got back in to my car and nothing!! no engine lights on dash and nothing from the engine  I have lights, stereo wipers, tried lock and unlock still nothing  next go for battery and fuses and after checking car comes back to life and drives home no problem.
I drive around for a couple of days no problem then dead again same problem! try all that I can think of and as I am at work I have lots of tools with me and after an hour time to give up as still no joy and leave my car at work 
Next day I called in a mate who is a auto electrician, he came round after work and we traced the problem to the terminal 15 voltage supply relay!!! (B1)

  by ds261, on Flickr

swapped out relay and alive she came all lights and engine starts first turn 

[pudding]

Good shout!  B1 must be the load reduction relay that powers up the starter motor solenoid and reduces current to the radio, HVAC etc whilst cranking.   Never heard of them going on a MK5 before, but good info for future reference 

[MIJ_JAGGER]

Defo good info
B9 is load reduction relay Kev

[pudding]

Cheers mate!  Swapping B1 and B9 over would be a good test then I guess 

[Rob1]

Yeah thanks for the info