Fuse S12, feeding Black/Yellow wires is used for both the rear heater fan and the AC control system. You will need to isolate them for testing. Just above the fuse box to the right is the connector for the added on AC system. The AC can be isolated there. If the AC has the controls overhead you can start looking there or in the relay area left rear pillar. Have fun. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of John Rodgers
Sent: Friday, December 12, 2014 6:43 PM
To: vanagon@GERRY.VANAGON.COM
Subject: '88 GL - Rear heater and ACJ

I've a friend who  has the '88GL and the rear heater has quit. It  somehow blew the fuse to the heater motor AND the AC. Now, it blows both fuses even when new ones are put in. Sounds like a dead short but how do you look for it? And how does the AC figure into it?

Anybody?

John