1999 XK8 freezing me out

Now that I am putting on some miles after sitting for almost 5 years car runs great. But, A/C does not want to keep a constant temp. Is there a temp sensor somewhere? Or is the control unit not doing its job? Any ideas appreciated

I had to pull out my ownerr’s manual for my former 98. There is a solar sensor on the dash on the left hand side (my car was a left hooker). If it is the same as the one on my former X 300, then the sensor is underneath two half domes; a white one under a black one. I found this out when I took it in for a detailing and the cleaners knocked the domes out of position. the AC ran max cold until I put them back. This could be your problem.

Very interesting. That cover is missing on mine. Asked at the shop about it and they thought it was some kind of light sensor, not A/C related.
Will see if I can find the parts.

I also had an X300 and vaguely remember the cap. Just made a cap for it from a screw cap, cut some slits and will see if this makes a difference.

The manual calls it the “solar sensor”. It s definitely part of the AC system. It is in the book under climate control. Its purpose is to detect the solar load on the interior and moderate the AC as necessary. If the cover is missing, then the AC thinks there is a lot bigger solar load and acts accordingly.

When the dome came off my X 300, I discovered there were two domes, sort of like nesting dolls, an outer black and an inner white dome. I do not know how they function but they both have to be in place for the AC to work right.

Were you able to solve the problem?

Made the little cap for sensor but have not had car back on the road yet.
Had taken the car in for smog check and passed. Car was not registered for the last 4 + years and went to AAA to register after being on non-op, $1100.
They said the DMV may waive the fees?
Now that the XK is up and running I am taking the E type apart to install 5 speed. The fun never ends.

If the cap you made doesn’t work, you should be able to find one in a wreckers. The XJ 40 and X 300 had the same system. I don’t know why, but you need the white one under the black one. Just one by itself doesn’t seem to work.

Follow up, the little cap I made did the job ! Hard to believe that is all it took.