Hello,

I've been trying to find the best AC amplifier available, and thought that caulfieldjag / John Cars was had the best option, but they are having supplier issues.

Any advice? The only option readily available is getting a used one for a bit over $100, but I'd rather not replace a failed part with a failure prone part... which may have also failed.

Thanks,

ROD

 

Have you tried calling Coventry West, Motorcars Ltd, Welsh Jaguar, etc to see what they have?

Cheers
DD

 

Hello Doug,

I did try Welsh (after failing with my other options) but they can only sell me a used one. They confirmed it's hard to find a new one. They also couldn't sell me a new In-Car temp sensor, which is another part I wanted to get, just to have better odds of having the AC work.

Thanks for the advice, I'll try the two places you suggest.

ROD

 

Well, if someone searches and finds this post, both Coventry West and Motorcars Ltd show the AC amplifiers on their web sites... for about $300!

I found a used one off a parted XJ6 which was "guaranteed" to be functional. Stop laughing, for $50 I took a chance. If this helps my troubleshooting, and was truly the issue, I'll consider the new part.

Thanks,

ROD

 

I also have one off a series III XJ6 that was off a car with "working HVAC". I've never tested it, but I bought mine for $90 which seemed like a good deal at the time.

Are you entirely sure your problem is related to the AC amplifier?

 

Hello,

So, used "good" amplifier is in, but no change. So let's assume it wasn't the amplifier (as opposed to me being ripped off with another bad amp).

Questions:

1) If AC amplifier is ok, will Full Cool mode depend only on the In-Car temp sensor?
2) Will the flaps under the blower motors ONLY open once the system recognizes it is in Full Cool mode (meaning I need to fix that first), of should they be opening anyway?

For those of you that are either very bored, or just extra kind and helpful:

This is what works:

Defrost: Opens the defrost vents, and closes the center face level vent. So all those diaphrams and the Vacuum Switch on the mode switch work.
Other blower speeds: Close defrost vents, open center face level vent.
Lower Heater Flap: Lower Heater Flap Actuator (driver side of HVAC unit)moves as I change to/from defrost.
Blowers: Both seem to be spinning.

What doesn't work:

Servo: Nothing moves, and therefore all linkage system is dead on passenger side of HVAC unit.
Flaps under Blower Motors: Always closed. I added vacuum directly (sucked on tubes) to the actuators and they opened. The flaps were cruddy and I tried to loosen them up a bit.

Next check:

In-Car Temp Sensor: I'd like to take the upper dash off and look at the sensor, clean up the connections, and try to trigger it by using the cigar lighter. Hopefully that will make Full Cool kick in.

Vacuum Solenoid: Not sure if I should bother on this, or wait until I can get full cool working. I believe this controls the Blower Flaps and that's why I think it may not be working, but maybe it will never trigger anything unless it detects Full Cool request from amp... (which depensd on the In Car temp sensor)

Thanks for your help.

ROD

 

Before you go checking all the temp sensors and such, have you checked to see if
1) there is refrigerant in the AC system
2) The compressor is getting power/clutch working

Start with the basics. If the compressor isn't coming on, trying manually jumping power to the clutch and see if you can get cold air that way.

 

I wonder if the servo is dead?

Unplug the servo. Apply 12v to the red wire and ground the purple wire. The servo should turn. Reverse the polarity to the red and purple wires and the servo should turn in the opposite direction.

Don't let the servo turn continuously. If it over-rotates you'll break the tiny switches.

Cheers
DD

 

Hello,

Based on info from pre-previous owner's mechanic (about a year ago, and no interest in lying to me since the car got sold to the previous owner):

Replaced the A/C compressor and its clutch assembly with a new one.
Replaced the receiver/dryer and one of the high pressure hoses. Evacuated, leak-tested, and charged the new system.
Could not get the body computer to command a cooling cycle from the car, but they could manually engage the A/C clutch with a switch and get proper under-hood pressures and operation.

So, that's when the next owner got the car, soon got fed up with the heat, and sold it to me not too long after.

I just checked the Servo as suggested and finally got to hear what it sounds like (never moved while I've had the car).

I need to run. My girlfriend's sister is about to give birth any moment now. If my girlfriend finds out I was working on the Jaguar... let's just say we probably won't be cuddling tonight.

Thanks for all the help.

ROD

 

Hello,

Continuing from where I left off above...

I saw another post discussing how fuse ends can be corroded enough, or the wire broken in a non-visible place, to cut the circuit.

Since I don't trust the previous owners, please let me know if these ratings are correct so I can replace all:

Behind Center Console Left Panel:
Black wire 3A fuse (AC Amplifier, correct according to Haynes Manual, Jaguar Service Manual says 1A C42648?)

Behind Center Console Right Panel:
Yellow wire 10A fuse (what is this for? screwed down. Service Manual C39462?)
Brown wire 35A fuse (again, what for?)

Under Glove Box area:
Brown/Blue 15A (Ranco switch? Does what?)

Off to the hospital again. I was born at night, just not last night. Joseph on the other hand....

Thanks!

ROD

 

Hello,

I changed the 4 fuses, no change.

Then I took the dash shelf off and the In Car temp sensor was not plugged in. So, with it plugged in, the servo now goes through the various positions, and the heat valve now closes on it's own in the engine bay!

My last problem... the compressor still doesn't kick in. I'm going to look for a used but hopefully "guaranteed to work" In Car Sensor.

ROD

 

Same issue I think. Can't get the heat to shut off? Pull the vacuum line from just aft of the V-12 engine that controls the air valves through the dash, and fill the vacuum tube with a golf tee. This fall, reverse the process. It may not be classy, but it works.
Old Rog
Tulsa, OK

 

Hello Roger,

Look at Doug's post on testing the servo. I applied his method to turn the servo into the cooling position. By looking at the right side of my HVAC, and diagrams that have been shared on posts before, I let the servo turn until I got to where internal flaps were in the "cooling" position. This at least prevented the hot air from rushing in. This new position of the servo also applied vacuum to the heater valve under the hood, so that closed up the flow of hot fluid.

As mentioned in my post below, a big issue for me was that my in-car temp sensor wires were not hooked up to the sensor. That was at least partly (if not completely) responsible for why my servo never moved. Now the servo moves according to the position of the temp knob... but I don't get cold air because my compressor is not told to activate. I used a hair dryer pointed at the hooked up in-car temp sensor, but nothing.

Taking the dash off was a pain. I don't think there are two similar screws anywhere on my dash, and many have partially stripped heads. Too many people got their hands on this car in the past.

Does your compressor kick in? If it does, you're one step ahead of me.

ROD

 

Near the compressor...perhaps attached to the mounting bracket or perhaps laying somewhere alongside....look for a square-ish three pronged "thermal limiter". This is actually a type of fuse and is part of the compressor protection circuit. If it is blown, the compressor won't engage.

Normally the only reason the fuse would blow is lack of freon. However, if the system was charged and otherwise functional but the owner or a/c technician was unaware that this thermal limiter even existed the result could be some head scratching.

For a visual Google "6551258 thermal limiter".

Any parts store can get one for $5.00 or so but it might take a little digging (or a veteran parts guy) because nobody (except Jaguar...heh heh) has used 'em since about 1978 :-)

Cheers
DD

 

Hello,

The old Thermal Limiter did seem blown, so I replaced with a new one. Clutch still won't engage. It is free to spin manually.

I don't want to blow any fuse/relay, so how do I properly manually engage the clutch? There is a two pronged coupler (not attached to anything) on the same harness as the Thermal Limiter. I believe one side is ground, the other was at 12V. What is that for? Is there a second Thermal Limiter anywhere else?

At least I got the system to the point where the temp knob does change the blending flaps, and full cool seems to work except for the clutch engagement.

Thanks,

ROD