It's a hybrid beetle owned by someone I know (not "hybrid" as such, just a mix of parts, I believe a later pan with an early body) running 12v with a genny, battery believed to be good, generator light comes on but belt is ok. Battery is believed to be good but will verify when I take a look at it. I'm thinking the voltage regulator might be stuffed. Seems like the system isn't getting the juice it should be.

Any other ideas? Regulators can be cleaned up and given a new lease of life can't they?

Could be ignition switch.

Owner has replaced the ignition switch with a new one. Made no difference unfortunately. Maybe the wiring in between?

Have you checked the earths on the head lights

loose "-ve's" on the headlight plug are notorious for dim head lights

Horns can just be rubbish

get a multi meter and check for 12 volts on lights and horn would be the first step

You really need a multimeter so you can check the charge voltage and then the light etc voltages.

With the engine running above 1500rpm you should get over 14v across the battery terminals. 13.8v is absolute minimum as genny ain't as constant as an alternator.

If the light still don't go out and you are seeing less than 13.8v then regulator is stuffed or could just be the brushes in the genny are badly worn. 2 things to check there.

Even without the engine running and a good battery showing 12.3-12.6v across it's terminals you should have good lights and horn. So first you check at the fusebox for those circuits. Both incoming feed side and outgoing fused side. Give or take a few 0.1 of a volt you should see the same as the battery voltage. Any less and it means corroded fusbox terms or ign switch is tired. Check output from ign switch.

If voltage at fusebox is OK then check at lights with neg lead of multimetter connected to a clean solid earth on the body. If voltage is close to fusebox then means you have corroded earth connection for lights. Same for the horn.

Most wiring faults in old VWs are down to bad earths, worn switches and old, oxidised wiring.

sounds like eaths as nearly every thing has an earth,first check battery than every earth you can find headlights taillights wiper you get the picture starte has a good earth

Went and took a look and the earth strap from the battery was almost entirely frayed through. Only about 1/3 of the copper wire was actually intact. I'm surprised it started at all. Plus the contacts were dirty and too large for the posts. They will sort all those things out and it should improve everything. Will also be cleaning the fusebox.

Interestingly, they replaced the ignition switch which is the in column type (fitted with later column) and now the car turns over but won't actually fire until you let go of the switch. This is a bit unusual - maybe mixed something up or just not getting enough power with the dodgy earth strap?

good thinking Joel