I've got two things I'm trying to sort out on my '81 xj6. The first one is the cruise control quit working. The on/off switch in the console has power and is working. There is no power to the brake switch or the servo. Bad control unit? If anyone has any ideas I'd like to hear them. My Haynes manual doesn't tell me where the control unit is so I need to find that out too.
Problem two, the heater/ac only works on defrost. Depending on the season I've been switching between two control units because I've got one that the a/c worked correctly and one that the heater worked. At some point I'll get a new unit but I wouldn't expect both of them to fail completely at the same time. Any thoughts? Thanks.

 

Did you check/replace the fuse?






Sorta below/behind the glovebox, on the backside of the bracket that holds the relays and RH fuse box. It's about the size of a pack of cigs and says "Econocruise"






'Defrost' bypasses most of the 'auto' functions/circuits. That's why it can work when the rest of the system can't. Have you found and checked all four system fuses? That's one place to start. Especially the fuse on the *ground wire* of the climate control amp...which is, I think, what you're referring to as a 'control unit'.

Cheers
DD