Hello Dave,
Have you checked the timing on the mechanism?
To do this scan the mechanism around to A1, now look at the stop plate assembly (behind the search unit) the large metal gear has a 00 mark on it, it has to be oposite the step in the search unit fixing bracket on the right hand side, if it is out you need to remove the search unit and the stop plate assembly and place in the correct positon. If this is OK then you need to check that the pins on the search unit are the the correct ones, I usually do this with the search unit removed and so I can see the pins punched out.
The usual test is A1, C2, E3, G4 etc i.e. upa letter and number each time on both the A sides and B sides. If they are out then you need to check your search unit wiper positions as per the manual.
Regards
Alan
Alan Hood
ami-man
UK