Mad Jock - check your PMs for a response in a bit more detail. I was searching for a PA38 wiring diagram on the Web, but the bu$$ers want to sting me over $200 for the privilege, so I went looking and found a Cessna 140 diagram (well, it isn't going to be that much different!).
Cessna 140 Wiring Diagram - see Page 3
I would check that the alternator field winding is powered and that all the cables are OK. Other than that, I've PMed a Web link for a UK second hand instruments supplier who has a couple of Low Voltage Warning Lights for £60+VAT +P&P each.
Seriously, if you need help, drop me an email or PM - I'm afaraid I didn't understand the reference to
PFA flyin on the 29th in Perth
- which month?, as Jun is the closest where 29 is at a weekend and neither the PFA or Scottish Aero Club Web sites show a fly in at Perth that day.
I do come up to Arbroath (the gliding school) occasionally, so I could always give you a shout if I'm going that wey.