I went out to the car a couple of days ago to a completely flat battery.
I hadn’t used it for a few days but it normally fires up, not this time not even the dash lights.
I had the battery tested and it came back good at 775cca so thats not the problem. They felt that the current draw was a bit high at 45ma so I spent this morning pulling all the fuses one by one to determine if any one fuse changed the value.
I was looking for a drop from the 33ma that the system settled at once everything had gone to sleep.
Nothing changed so I have come to the conclusion that the video camera must have been on and flattened the battery.
Any how, going out this morning I tend to use the cruise control even around town.
I engaged it and it seemed OK but then there was a hill that I had to go up, the car started to accelerate and it just kept going, and going and going I eventually chickened out at 70klm/hr (residential area)
Seems to have settled down now but just wonder if anybody else has had this sort of behaviour happen to them after disconnecting the battery?
Checked current draw on my 1980 xjs, key off, draw 11ma, less clock 4ma, less radio 1ma
Never had the cruise controll problem.
But I did have the battery drain problem on my x305. Did you pull the fuse for the alarm system? That was the problem on my car. I never got to the bottom of it. Shortly after I discovered it, the car got totaled by a lorry.
Similar problem with my 1998 308. Drain traced to the heated windscreen relay not switching off - cycling a few times settled it down - then electrical gremlins after re-connecting the re-charged battery. Left battery disconnected overnight to allow residual charges in the car systems to dissipate, then reconnected and all OK. Somewhere in the ROM is a section saying you MUST allow time after disconnecting before reconnecting the battery if I recall.
Your cruise issue sounds like the + button sticking/shorting.
Frankie
I pulled all the fuses in the boot and the two fuse boxes in the engine bay, I know to let the system to go to sleep before testing the drain. I closed the latch on the boot to turn off the boot lights.
The speed only started to increase once the engine started to increase power to overcome the grade so I don’t believe it was the button sticking.
30-40mA sounds ok to me
Agreed Andy been so on my XJ40, X308 & X300! A 1980 XJS didn’t have much by way of electronic modules to cause drain I would guess.
Thanks guys, it settled at 33mA so will see how it goes, now all I need to do is fix the float in the l/h rear wheel bearings 
might just replace the unit with the spare hub that I have from when I blew the diff.