winter is almost gone but i want to sort this out. The heat was working fine then quit, a couple of days later it worked on the journey into work but nothing since then. I've checked all the fuses i can find and they seem ok, if they looked iffy at all i changed them. with temp set at 75 when i turn on the fan i heard a sort of clockwork noise like it is trying to do something then repeatedly tries to do it again when it fails! i have an haines manual, however the delenair unit shown seems to be different from mine on the top half of the unit. i did identify a spring that was not in its correct place but this has not made any difference and i still have a spring in this area that is unconnected!

 

Mmmmmmm.

You appear NEW, so welcome to the REAL world of motoring.

Your '85 a/c is known as a Delanaire 2.

The "clockwork noise" is the servo drive, on the RH side behind the fan switch, doing what it does. This operates the levers and springs etc to acheive what is called for by your settings of the 2 knobs.

This servo is "driven" by a small ECU, tucked up behind the radio, and BARELY accessable via the LH side when ALL the relays and such are removed, British engineering at its very best I'm afraid. These ECU's fail from time to time and there are many aftermarket units available from the suppliers linked to this site.

There is an EXCELLANT description and trouble shoot, setting procedure in a book by Kirby Palm, it is called "Experience in a book", and is XJ-S V12 derived, BUT, the Delanair is the SAME.

The book is downloadable and FREE. It is 700+ pages long, but I honestly believe a good read for any Jag owner of this vintage.

I have reset a few down here that have been messed with by "experts" and I used the "book" each time. Our RHD make it easy, NOT, so LHD should be a snap hahahaha.

 

These climate control units can be tricky to troubleshoot... But here are some suggestions...
You didn't really say if there is absolutly nothing happening when you turn on the A/C or heat... If nothing at all (other than hearing the servo run) happens, it's likely the fuse or wiring going to the 50amp fuse that runs the blower motors. The socket that holds the fuse can get loose, and the fuse not make contact.. Or the wiring in the back of the fuse box is faulty... It's on the RH side, in the middle. This applys if there is no air coming out of the unit, either hot, cold or defrost.
If you are getting A/C, but no heat, check the heater valve on the firewall. Open the bonnet, the heater valve is the mushroom looking canister in the middle. When you turn on the heat, the valve should be seen to move, allowing coolant into the heater core. If it doesn't move, it could be frozen shut... Try to open it manually.. If it doesn't open, there is a problem.
If that's ok, literally feel the hoses coming out of the heater core (LH side, from the firewall, stacked on top of each other)... they should both feel warm when the heat is turned on. If not, flush the heater core...
If you have full A/C, full heat, or hot defrost, chances are pretty good that the amp or servo is faulty. As Grant says, the amp can be a pain to get out, but you can simply leave it in place, and hook up another one... Just leave it tucked behind the kick panel, plenty of room there..
If you don't have A/C either... First check to see if the clutch on the compressor is turning. When you have the car on, the pulley on the compressor always turns, but without the A/C on, the clutch is stationary... Turn the A/C on, and the clutch will start to spin... It's directly on front of the A/C compressor pulley... If it doesn't, then for whatever reason the signal to the compressor isn't quite connecting... Could be a blown thermal fuse, faulty switch in the car, bad amp....
So lots of possibilities, but check the basics first... If everything above seems to be working, then it will be time to dive into the Climate Control unit itself.... oh joy!

Cheers!
David Boger
Everyday XJ