Yes check the ground to the battery.
Good luck

> Date: Wed, 17 Aug 2011 14:02:42 -0700
> From: camping.elliott@GMAIL.COM
> Subject: Intermittent charge
> To: vanagon@GERRY.VANAGON.COM
> 
> Hey all, I'm sending this from a primitive campsite in the Deschutes Nat'l Forest. The last 3 miles to this location the alternator lamp came on and battery voltage (dashmount gauge) dropped. Managed to find a nice spot anyway. After engine cooled, started it to check alt output and it was working again. Have spare regulator, will swap it in. Anything else I might look at?  Mrs Squirrel will be joining me tomorrow and could bring things if anyone thinks VR might not be the prob. 
> 
> Sent from my smartphone with tiny screen & even tinier keypad.