Hello all,

My recently acquired,(2007 XJ8) has an issue with the AC cutting out intermittently. My mechanic says there is nothing he can do at the moment because technically the AC is working. The AC will run and shut off for a few minutes randomly and then turn back on. Any advice or thoughts?

 

"Recently acquired.." meaning you may not have yet familiarized yourself with an X350's climate control system?

You may or may not have a fault.

The system cycles the AC compressor as it sees fit - even in the dead of winter - (as a dehumidifier aid to defrosting).

Likewise, there are 'zones' that may not have the same temps to satisfy.

RTFM. Play with it.

It seems to have a mind of its own, an annoying one, even. That said, it is "usually" just trying to deliver the outcomes(s), multiple, being requested of it... and in as stealthy and drama-free a manner as it can manage, too. EG: no roaring blast of chilled air to impress the heathens.

Ask it for 68 F? It quietly delivers 20 C.

Or the reverse.

Go figure.

 

My first thought was that the car's AC system might need a recharge, and that would likely be true for most Jaguars of that vintage. In fact, I have to recharge my 2005 Jaguar XJ8L's AC system every summer.

 

Hi Rickkk,

if you have to recharge the AC system of your car every suumer, then it definitely has a leak that should be repaired. Not only because of environmental issues...

ACs in cars cannot be 100% loss-free, because of the combination of metal and rubber tubes, but the average loss of coolant is around 10% per year if everything is in order.

In fact, the last time I have recharged the AC on my SV8 (built in September 2003) is some 5 years ago, and the AC still works fine. I was planning to check it anyway, so once I do, I can tell what the coolant loss was since the last recharge.

Best regards,

Thomas

 

Do I understand correctly that you mean that the AC in your car does not manage to keep the temperature that you have set? If it cuts off intermittently, but manages to keep a constant temperature in your car, then it works normally.
If not,I agree with Rickkk that you should try to have it recharged. If the coolant level is too low, the system will not be able to keep the necessary pressure and the pressure sensor will make it cut out to avoid damaging the compressor.

Other faults could be one of the different sensors present in the system being faulty, or the compressor itself.

Thermite's statement is not entirely correct, as, yes, ACs will also run in winter to help dehumidifying the air, but only if the outside temperature is above app. 4 degrees Celcius. Below that temperature, the compressor will not work, even if the AC is "officially" on, to avoid the built up of ice in the system.

Best regards,

Thomas

 

Ermmmm... ???

Recommended reading:

https://www.ashrae.org/technical-res...shrae-handbook

Mind.. it had fewer pages back when I last did the whole lot - 1970's. FAR fewer!!!

 

Your mechanic needs to hook up gauges and see the high and low side pressures as the a/c is running. Then make note of same pressures when a/c turns off. By turning off i mean the compressor quits turning via the clutch. There might be a problem of excessive high pressure or too low pressure. Watching the pressures gives you a good idea of where to troubleshoot

 

Well yes. Ideally, the AC system should not leak refrigerant. However, given the age and mileage of my vehicle, it simply wouldn't be prudent at this stage to repair the AC system. You know, I sure wish that the auto AC manufacturers would finally put some quality into their products as most of these systems typically do not last more than a few years.

 

Thank you Thomas for your input. The AC does not seem to maintain the set temperature. It will run and then everything shuts off and everyone starts to sweat in the car since it is usually over 100 degrees outside. Since there are no codes showing and the AC does work, my mechanic who is Jaguar specialist says we have to wait and see if any codes come up. I wanted to reach out to the forum to see if anyone had similar issues so that I could explore other possibilities. This is my first newer model Jaguar (2007) and I am still learning about it. I have two 1997 XJRs for reference.

 

Kay094809 -Assuming you will bring it back to the mechanic, and, he is a reasonably competent HVAC guy, I suggest;

1. Bring it back to him, and ask him to drain (recover, remove) all the 134a freon from the system, then place it under vacuum and make sure it passes the leak up rate.

2. If vacuum fails, then fix leak. Common spots are the Schrader valves on high and low side test ports, and the o-rings on the aluminum pipes / coupling where the Freon enters front condenser (the radiator-like unit in front of the coolant radiator). The original composition of these was changed to a more durable material a few years ago. If it does fail, he can inject some UV dye that makes it very easy to locate leaking component (been there, done that).

3.If vacuum passes, the the quantity of Freon should be refilled with Jaguar-spec volume. This is 23 ounces (650 g) 134a Freon & 5 oz.(140 ml) oil for the standard system, and 28 ounces (800 g) 134a & 6 ounces (180 ml) oil for the four-zone system. There is a label under the hood that will clearly list (the Freon quantity) your car has.

4. Outside of his labor, the Freon and oil is very cheap, probably less then 50 bucks. And you get the peace of mind that the system was recharged by weight, not the somewhat guesswork of most folks using pressure. As mentioned earlier, the compressor will cut out (assuming you meant it blows warm air intermittently); if the system pressures are too high or too low, in order to save the compressor from catastrophic failure. I can't tell you how many cars I've seen under and over charged by well meaning owners and mechanics.

 

Listen to scottjh9?
We need high and low side pressures and inside vent temperatures. No other way to tell.

Starting all over from scratch like what's posted above would be a great place to begin. You can't tell how much refrigerant is in the system otherwise. You might be over charged or under charged?
Also the UV dye is in it from the factory so get your black light flash light out and take a look.

Since it's working but cuts out now and again you might have a failing magnetic clutch or even a compressor that's starting to go out and is getting harder to turn?
Can you tell if the compressor is kicking in and out when it does this?
How many miles on the compressor?
.
.
.

 

Fear not.

The AC system is arguably the most reliable part of the entire motorcar. Even if/as/when it NEEDS repair, it is likely to STAY repaired for very long years!

START with the "cheap and easy"

- cabin vent outlet temps. Each of several. The old skewl mechanical dial thermometers can be had for under ten bucks, each. You may even already have one in the kitchen as a meat thermometer?

- Mark One eyeballing the AC compressor clutch is cheap, too. It SHOULD be 'cycling' periodically, but not chirping or squealing its belt nor chattering.

No serious spend so far.

Then...

Do your own due diligence before selecting further test gear. There is 'too much' of it in the market for fast, blind, choices -

You can benefit from the same 'pro' grade gear we who do all MANNER of refrigeration gear accumulate... but it need not be that expensive. Mebbe $50 to $100?

Surely pays for itself if you can even be more AWARE of what you will be asking an AC shop to do, NOT do, or go the extra mile to PROVE an itemized portion will be necessary.. or at least explain why it would be 'wise'.

 

The smell I got from very slow leaking refrigerant was not unpleasant - a bit like mown grass.
Did not smell like swamp.
Looking for leaking colored refrigerant under the parked car revealed nothing, presumably because the leak was so slow.
Eventually the AC began misbehaving and died.

 

First there is no colored refrigerant? There is UV dye put in the oil so you can use a black light flashlight to look for stains.
Next you will never see a puddle because at normal temperatures and pressures it's a gas only?

Listen to scottjh9 and get some pressures and duct temperatures. If you really want to do it right follow what ctsemicon posted above?
Vacuum the system down and check for leaks then recharge with the proper amount of refrigerant.
Now you have a proper baseline to start from.
.
.
.

 

I did not mean that the refrigerant itself would be in a puddle under the car.
Obviously, it it is a gas at atmospheric pressure and vaporizes.
Sorry if that was unclear.
However, some refrigerants have a visible yellow/green dye added that may show up depending on how large the leak is.
Others, as you referenced, have a UV dye added that can only be seen with a black light.

 

Sorry I was not clear but the UV dye is added at the factory. No need to add more?
.
.
.