I know that this subject is raised again and again (and again), but I have some questions that I hope someone can help answer.

I have a 1985 series 3 XJ6, and this is one of the last things that I want to get sorted out (for now anyway)

My aircon is not working. I am not too worried about the actual refidgeration at this stage, I just want the rest of the system to work properly.

The symptoms are as follows:

Most of the time the blowers won't come on at all, but I can usually hear the servos moving behind the dash. (and have seen one moving as I have removed the left footwell panel to access the ac amplifier)

When the blowers do work, there is never any change in temperature, no matter where the temp dial is set. The temp is just very slightly warmer than the outside air. Not hot, even when the car is fully warmed up.

If it put it to "def" and the fans are blowing, more air does blow out onto the windscreen, but it still blows a lot of air out of the center vent.

With the engine running, and the fan blowing, I have looked at the hot water tap/valve thingy, and with my daughter changing the temp and fan settings, the tap never moves or changes.

If I remove the vacuum hose from the hot water tap/valve, it does close instantly.

When I try and turn on the blowers, and they don't, I can hear the fan relay black box thing making clicking noises, but nothing happens.

I got another a/c amplifier delivered today, and I installed it, and it made absolutely no difference.

I am at a loss, as I have no idea where to start. I thought it was the ac amplifer, by reading other threads on here, but it doesn't seem to be the case.

HEEEEEELLLPPPPP

 

My info at the moment, more thinking wil be needed.

Doug, the S3 Guru will see this and chime in when the time zones align.

The tap lever dropping down when you remove the vac hose is in fact ON. That is the default of those taps. So with the hose connected the tap lever is UP, so OFF.

The fans not working is probably the micro switch pack INSIDE the switch assembly on the RH side of the unit, and a MONGREL to get at, and even harder to work on.

What I have found with my S2 cars, same system, is that the 2 SMALL setscrews that secure that RH switch pack to the dash panel come loose with age. Acces is messy, radio OUT, the fascia panel OFF, and you will see the 2 screw heads either side of the RH switch shaft, and inside, via the radio opening, are the 2 nuts, so let your imagination run wild, and tighten them up. NOT dumb tight, just "nice and firm" will suffice. This has fixed 4 out of 4 for me over the years.

If that fails to proceed the fans, Doug will have more to offer I feel sure.

The temp side, LH switch unit, is a simple rheostat, and may be simply dirty from lack of use, so a good clean may get it going, then again it may not.

With that vac hose OFF you should get HOT air inside the car, just uncontrolled.

 

I'm not sure if I can live up to 'guru' status on this....but I always appreciate Grant's faith in me . The system is virtually unchanged, Ser II cars versus Ser III cars, so Grant's remarks are 100% valid.

I have to do some mulling and report back. I don't predict a "This is easy. All you have to do is......" type of answer. It's tricky diagnosing these systems as so much sequenced, chain-reaction activity is at play.

As for the blowers specifically.....Do you have the wiring diagrams? Next time they are in 'inoperative' mode you could check voltages and perhaps at least narrow down if the problem is upstream or downstream of the relay pack.

In the meantime here's some info excerpted from the Delanair manual that might be helpful, if you don't already have it.

Delanair Mark II Automatic Climate Control

Cheers
DD

 

check these two items:

check the check valve located in a vacuum line hanging near the battery which comes out of the firewall, a little black and white plastic check valve.

0) observe and remember the orientation of the check valve before removing it;

1) remove the valve and blow through it, blowing one way should allow air to go though it, blowing the other way should "close" the valve. Do this a number of times to see if the response is always the same. If not, replace the check valve or put it in a pan of warm water with dishwashing detergent for a while to see if it unsticks. They get sticky with age and the ball inside sticks. This vacuum line is connected to the SERVO, if the check valve sticks open or closed, the SERVO does not respond correctly.

2) Blowers: blowers not running could be:

a) the large black Blower relay found on the driver's side behind the Vent panel.

Remove the two screws holding the black plastic floor vent, pull vent, and then pull the panel towards the front of car to release catches. You will see the large black relay with 10 wires connected to it. Check all connectors are secure especially the center connector with a screw through it. Run engine, set control to AUTO and TEMP to 65. Wiggle each wire to see if any response from blowers.

b) No response? substituting the existing relay is the way to eliminate the chance of a bad relay.

 

I have ordered a new relay as the one i have has a couple of corroded contacts and a little burn hole in the side.
Looking at the diagrams, is there any chance that the water temp sensor is causing the fans not to blow?

 

leave that alone until you replace the relay. Those other parts rarely go bad in 1980's XJ-6.

a future step for your car would be maintenance of each blower motor case, a difficult but satisfying job for which you need the Factory Service Manual which you can download here. Study each step before attempting the removal of each blower case, the first time is the hardest. The cases get full of dirt and grime from centuries of use, cleaning them and fixing any broken linkages inside the case (the linkages do break), and replacing the foam seals which desintegrate after 20 years.

 

Agree with Jose.

I would check the EARTH wires from that relay to the stud just forward of it, which is also used for the front mount of said relay. I have had 2 where that wire was not connected at all, and many hours wasted diagnosing the system, when all that was wrong was the "fiddler" before me had left that wire off when refitting that relay.

 

The one on the heater pipe? Yes, good thinking. If it doesn't close....or the connections are weak.... the fans will not work. Just bypass it and see if anything changes! Remove the connections and use a small bit of wire or a thick paper clip or similar to join 'em together



Cheers

DD

 

Thanks for posting the Delenair Info. While looking through the pages I started to wonder how all this works as a complete system for any length of time. There seem to be so many failure points. I feel very lucky I have a working system and not particularly looking forward to the day that onion needs peeling.

 

I had problems similar to yours, tested all components, and turned out the mode switch, the rhs black knobbed switch, had a bad a microswitch in it. Bitch to replace it but system works great now.

 

Replace ALL of the micro switches, including the controller micro switches.
Be sure to replace all of the vacuum tubing, too.
This got my AC working. Replace the water valve every 3 years, too.
And use propylene glycol and distilled water. I also use water pump lubricant.
This will protect the head and block water passages and outlast the ethylene glycol anti-freeze.
New replacement switches are much better quality and are only around $2.00@.
A good electronics supplier has them.

All Electronics | Electronic and Electro-Mechanical Parts and Supplies at Discount Prices

 

That is it!! Propolene Glycol. A bit more critter friendly ion case of spills.


Way back when, my AC worked. But, at times not. On reflection, it seems that vacumn was an issue.


But, on the day of the DOHC's demise, I was in Stockton on business. A very hot day, but the AC was cooool.


I've read my Dellanair manual and a bunch of posts on this forum and another. It seems that I think I understand, then suddenly realize I don't!!u


After the swap, I've not charged it. Mebbe this summer????


Just got the crank start issues fixed, I think!!


Carl

 

I have replaced the black relay, and the a/c amp, and the blowers work every time now. That is the good part.

I think the temperature control is not doing anything at all. There is absolutely no change when I turn it. Maybe knocked a wire off when I changed the stereo, i will have to pull it out again one day to check. That is a snot of a job.

Also, the center vent is still not closing when I select Def. Would this be connected to the temp settings or a different problem again?

Cheers,
Richard

 

great! the large black relay is really 4 relays-in-one. If you open the old one you will see.

but it doesn't control the amplifier, only the blower speeds even though the whole enchilada is related.

you have resolved one issue;

Now look at the Heater Valve in the engine compartment, center of firewall / bulkhead, while someone else moves the TEMP control to min and max temps. Do you see the heater valve linkage moving? (opening and closing).

 

Done that. No, the heater valve does nothing. I have checked by pulling the vacuum hose off, and it changes straight away. It seems to be a working valve (except it leaks a bit of coolent for some reason when the vac is applies). It is as if there is no command to change the temp. If I put it to 65, there is no change, the compressor doesn't change its behaviour, there is no servo noises closing the fresh air flaps, and absolutly no change. Same if I put it up to full temp. No change at all.

I have taken off the right hand panel as well and checked all the vacuum tubes, and the all have vac, except for one, but that did when I changed the setting to Def, so i was able to identify that as being the windshied vents. Any clue as to what colour the vac line for the center vent flap is??

Anyone got any other suggestions for me to check when i pull out the stereo?? It is a horible job and I don't want to do it twice

Cheers,
Richard

 

the 1985 Heater Valve is NORMALLY OPEN / CLOSES WITH VACUUM.

based on what you say, I suspect the heater valve is bad, especially if you do not know its history, and especially if it is leaking, it most likely has a broken diaphragm inside, I would install a new one.

the temperature change is controlled by the AMPLIFIER which is controlled by the TEMP selector. These amplifiers are known to perish after a good ten years of use.

if you know for a fact that your compressor has a refrigerant charge, then the issue is the amplifier, located behind the radio mounted on a spring bracket and connected near the large black relay with a white connector with many many little wires.

the flaps / vents are controlled by the SERVO, with its many microswitches and vacuum input.

the vacuum tubes can be seen in the picture below.

 

The servo is what sends the vacuum signal to the center vent and the water valve. Inside it are vacuum switches which open and close depending on servo position controlled by amplifier.

 

O.K. I have replaced the relay box, and the a/c amp. I have got the blowers working properly now. I used a multi meter on the wires coming off the temperature dial. At one end it showed 0 resistance, and at the other it showed nearly 10 (can't remember the units). I adjusted the dial and the resistance changed accordingly. I conclude that the temp selector is working.

The center vent is still staying open all the time. I removed the black vac hose as a test, and the vent closed. The vent flaps work then. I did the same thing for the water tap, so i conclude that the tap works as well.

What controls those two units?? how do i test it, and how do i even find it??

It's driving me a bit mad. It feels a bit like im flogging a dead horse lol



Cheers,
Richard.

 

Oops, sorry, I didn't see your reply. Thanks. Same question though. Where are the servo(s) and what do they look like?

Thanks

 

the Servo is a precision piece of machinery that looks almost like a miniature crankshaft.

it is located in the opposite side of the radio console and behind the vent panel; If it has not been messed with, it has a black plastic cover over it, very thin plastic, same material as the tray under the center console lid. The cover is held by plastic push-in fasteners that need to be pried up, then you can remove the cover.

With engine running, transmission in PARK, MODE switch set to AUTO, you can watch it in action as well as the flap linkages. Observe the linkages to see if any of the "detent" set-nuts are loose, as you turn the TEMP knob from 65 to 85.

see attached images and the PDF doc