right on my 1.8t agu i have an electrical issue which is,
the power dims, lights flicker, and the abs light flashes and usually says a mixture of these things, brake fault, alternator workshop, service manual, stop....and also beeps which really does my head in!
now its got a brand new batttery and had to new alternators and been checked by a local auto elecy and all they found was a faulty earth on the gearbox.. they checked the whole car over all earths and as much wiring they could find. a mate at halfords checked the battery and said its fine
now when i do the windows they seem to take the power which usually sets this off but as its so random and i really mean its random. but other times it just does it when the car seems to go above 20 mph. i have checked the battery and its getting the right volts but when this drop happens it goes down to about 12.3 volts for a split second then back up. i have also done the usual of checking the fuses on the battery and fuse box. also the black box under the dash board the convenience control unit clicks like mad makes the dash go mental. also sometimes i cant lock my car, the alarm sets and flashes but the door pins dont go down but the boot will lock. this happens for like 5 mins then go back to normal. plus sometimes the alarm goes off when i lock it and wont turm off.
now this fault is reaaaaaally intermitent, and usually goes away when i turn the car off.
the only fault code i get is battery power supply terminal 30 low voltage
if i think of any more info ill add but theres my fault i dunno if its all connected but try and help figure it out

vw say it could the the black box but they need to plug it in to find out
also vw say on my agu 1.8t 99 im supposed to have a 109 relay is that true??