Got the refrigeration system all together: complete flush, rebuilt A6 compressor, new hoses, expansion valve, and drier, plus the correct lube. I took her to my local garage buddies to evacuate and charge with R134A and it is nicely cold! I mean Cold! I could not be more pleased with the temperature at the vents.
Couple of issues have presented, which I could not be cerrtain about until I got the refrigeration system working: works great on high blower; it responds to the temperature setting (left control) pretty-much as I expected (I've never experienced a new one, mind you...),in that, if I turn it to a warmer temp, it seems to be blending warm or heated air in to raise the temperature of the output air at the vents. if I put the right selector on AUTO, it will respond, but as it backs the blower speed down, the speed surges up and down several times and I can hear a repeated faint whirring sound from inside the dash. It usually but not always will settle to the lower blower speed eventually. Also, the low setting on the right control results in no blower. All this is with the slider underneath the radio in the left side (where the blue symbol is).
Any ideas on troubleshooting and repair? I admit I expected trouble here; after all she's got some age on her. I also experienced similar issues in HEAT mode when trying to operate in AUTO, otherwise plenty of heat, and again, no low blower speed.

 

The whirring is actually a good sign. That's the reassuring sound of an operational servo. Mind you, the whir alone doesn't prove that the servo is functional is all aspects. But, at least it isn't dead.

That said, the surging is most like a wonky amplifier.

Can't hurt, though, to make the the cabin temp sensor is clean and the tubing is attached. I had some weird problems once and discovered the sensor tube had come off. The sensor is under the top of the dash....you can see the inlet hole just above the glove box door. Removing the dash pad just takes a few minutes if you wanna give it a whirl




"The lower" or "the lowest"? What you experiencing might be normal depending on setting and conditions.

In 'auto' mode, when the system is in cooling mode the top 3 blower speeds are used. In heating mode, the bottom 3 speeds. In blending mode....I can't remember. Maybe all 4 speeds. Defrost is highest speed only.



Well, this is clearly a fault and may well be realted to the (possible) problem you mentioned above.

The relay and the resistor are both suspect. They can be tested. Do you have the good S57 wiring schematic and good eyes? It takes some patience to figure out the circuit.

Checking/cleaning relay and resistor connections first might be a good idea.



Almost impossible with the service manual or training manual. The latter is best.

Cheers
DD

 

Training manual, updated by a jag lover years ago. With a bit of searching you can find and buy a reproduced training manual

Delanair Mark II Automatic Climate Control


More reading but might not be quite what you're after

Duncan Brown's unfinished Delanair amplifier project

Cheers
DD

 

Doug needs to be Knighted to Supreme Advisor of the Order of XJ-6 Fanatics.

 

And you, too Jose ! We've learned plenty from you over the years

Cheers
DD

 

not as much as I've learned from you Doug, so I'm happy to remain a lackey!

 

Thanks to booth you guys! Great help like this really makes my car hobby much more gratifying!