Well short of contacting AF for a wiring diagram/replacement recommendation or SafeTAlert for recommendation I would test the leads and insure one you use is always hot irregardless. IE with shore power/without, battery etc.
Most info Ive seen just recommends connecting to camper power supply (without identifying which one) and cap remaining wire, some RVs just had multiple 12v input wires. However, to be sure, I didn't note model numbers, some CCI third wire (yellow I think) was to solenoid valve that shut off gas...if thats the case a little more involved.
As a lot of these older CCI have been replaced (or need to be) I'm surprised theres not more definitive how tos.
edit did find this cross/over link
http://www.mtidealer.com/images/MTI-CCI-Cross-List-Propane-Alarms-2012.pdf