Hello all,

Have picked up a Series III 1986 Sovereign... first Jaguar for me! Drives really well and sits nicely on 110 km/hr on the freeway. Very happy.... but, you guessed... there are things to fix. Highest priority... heating/cooling.

Plenty of cooling... no heating. Been reading through posts on the forum and have started the fault-finding diagnosis.

First thing I have checked is the water-tap vacuum switch, inside engine bay, attached to firewall. Seems new (probably a Ford one) and appears to be working correctly. (I took it off the car and ran water through it. Valve shut off when manually operated and the tap responds when connected to the vacuum pipe.)

So what might be next.. I realise that there are lots of possibilities, so I am starting with the most likely/ most accessible/ cheapest, options first. ( I will be looking for horses first before I start looking for zebras!)

Anyway, pretty happy so far.

 

Good that the valve seems to be working off the car, but is it working on the car? When heat is called for there should be no vacuum at the supply hose

Before going deeper, though......

When you operate the temp control knob do you hear a faint whirring sound? You should, as it tells you the system is trying to obey commands.

Cheers
DD

 

Thanks Doug,

Yes, ... there are noises!

I set the temperature to "75" and set the fan to "auto". After about 3 minutes I changed the temperature dial to 85 and set the fan to "low". I can hear various noises and a "click" with corresponding small change in engine idle speed, as though something is trying to do something.

No change in temperature though.

I have had the footwell sidepanels off, hoping to see something move, rotate, open, close or just do something... but nothing yet.

I do not seem to notice any change in air flow when I rotate the very bottom lever, (under the radio). What should I notice when that is moved from left to right?

I have left it centred for the moment.

regards,
Rhys.

 

The whirring is the "servo", a mechanical device that moves (some of) the flaps. So the system is at least fundementally responding , which is good.





With the right "cheekpanel" off you should seem some metal rods and linkages with bellcrank-type levers. As you make gradual changes in the temp setting these rods and levers should move. After any change in the temp setting it takes a few moments for the system to respond. If the rods flat-out don't move we'e got problems




It has nothing to do with air flow. It alters the upper versus lower temperature bias when the system is stabilized in blend mode. In other words, if your feet are fine but your face is a bit too warm or too cool, this will adjust the temp of air coming from the upper outlets. It is a very subtle adjustment.

Cheers
DD

 

Thanks for taking an interest Doug,

I will be more patient and watch for any signs of movement of levers, linkages etc. after I change the temperature setting. It will have to be later in the week, but I will post the results.

(Actually spent 12 months in Washington State... all of 1987, much further north than Longview though.)

regards,
Rhys

 

Problem Solved:

Thanks fro the help with this problem. It has now been solved. Apparently it was a "dry solder joint". When the airconditioner was unplugged from the loom, and a test device plugged in... everything worked. The conection was resoldered and I have been warm ever since!

thanks,

Rhys