Thanks for all the help ILUVMILS, it is very much appreciated.

Where can I find that pin - I looked on the PSA pump and didn't see it.

The panic, including the horn works (never tried that).

I also found a lead coming out of the firewall with two wires cut - looks like it could have been to a siren which is no longer in there. I also found a power lead jumped onto the positive harness at the battery - presumably for the alarm. I cut it, but nothing happened (car still clicked), so I reconnected it.

I'm convinced it's tripping the anti-theft, sans the horn, but the fact panic is working with the horn stumps me. I'm not that good with electronics.