Hello everyone
has anyone replaced the ac expansion valve known as THX valve on a 2003 4.2
I have been going though what KR98664
had written but are no farther ahead
Only two things that could be wrong
Have a blocked expansion valve/THX valve or our new ac compressor is faulty
system holds vacuum left for 30 hours
Ac took 400 g of refrigerate no problem done sitting on scales
manifold gage set read low side 50 psi high side 45 psi will not move from that
With ac clutch Engaged engine running ac on low full blast
had checked fuses and relays all working
New bosh dccv valve working as should as when turn heat down on climate control temp on pocket thermometer drops on all vents
I have tried 3 of my rebuilt climate control modules
all 3 have the same part number
Makes no difference
has anyone replaced the expansion valve
In person as we all know manual makes it look easy
Thanking you
​​​​​​​Darrol

 

Related or not, dunno..

I had that with one of the X200 V6 cars.

New comp, regassed, odd stuff at the vents. Heater valve 7 days old and fine.

The Gas guy (we be banned from messing with re-gassing over here), suspected the TX valve..

His other man said NO WAY, that dash needs to come out.

A very brave decision was made to give the beast a GOOD FLOGGING, with the AC on. He drove, I am not that brave anymore, and about a km down the road there was a POP, and the beast was normal, the AC was cold, and did what i was meant to do.

Suspect was a jammed/frozen TX valve, apparently not uncommon, and for some reason that harsh flogging sorted it.

Never looked back, all good for many years now.

A tad brutal I suppose, but ot worked.

NO idea if the X202 is thesame set up, but what harm can ot do.

 

As a general rule when troubleshooting, offered in the kindest and gentlest spirit possible, it's best not to run around like a chicken with its head cut off and then condemn the most expensive and/or hard to replace components.


Right off the bat, that is NOT the symptom you'd see with a blocked expansion valve. Instead, you'd have very high pressure on the high side, and very low on the low side.

Could the expansion valve be stuck open? Possibly, but that seems like a very remote chance. I'd be tempted to use a screwdriver handle and tap the expansion valve a few times to see if it will free itself. Do NOT tap the flying saucer chamber on the end, as you don't want to damage that. Tap directly on the valve body.

Judging by forum experience, the expansion valve seems to be very reliable. We have very few reports of failure. If I had to wager on the typical failure mode of one, I'd think debris blockage would be far more likely, but remember your symptoms do not match. As lazy as I am, I'd want to conclusively rule out all other possibilities before tackling that MAJOR project on a hunch. Apparently the expansion valve was the first part sent down the assembly line and the car was then built around it.

You mentioned working through the troubleshooting guide, but did you work all of the steps? Specifically, did you do the test with the paint marks to check for slippage at the compressor clutch? If you have a wiring problem in the clutch circuit, even a brand new compressor (with clutch) will slip. How about the amp draw of the clutch coil?

How about the serpentine belt tension? Does the power steering seem sluggish, especially at low RPM? That's another symptom of a slipping belt.

If you still have your heart set on replacing the expansion valve, this video has some details:

 

If the vehicle has the 3.0 litre engine, the expansion valve can be reached without needing to remove the dash.

If the 4.0 litre engine is fitted, the inlet manifold can be removed to reach the expansion valve.

 

I had a similar problem last year. Replaced a/c comp. Then condensor. Got a full charge in but no cooling and no refrigerant movement to speak of. Finally took some line temp readings and found a potentional blockage up by the condensor on the condensor inlet line after it leaves the comp and after the pressure switch. There is a 90 degree bend of the line and before the bend i was getting 110F andabove and after the bend it was 70F or so. I took the line loose at the condensor and at the comp and backblew compressed air thru it. Regassed the system and everything worked great until the power steering pulley rubbed the line because i forgot to secure it. I have a saga thread regarding the whole affair. Karl and clubairth helped a lot. Go to my profile and search threads by me. It is the top one about a/c question

 

Here's that thread:

https://www.jaguarforums.com/forum/s...mation-282778/

From a cursory read, you were seeing some pressure difference between the high and low side, right? In the current thread, he's seeing almost no pressure difference. Big difference in how to troubleshoot, so I want to make sure we're on the correct path.

 

One more thought is a defective test set. If test results don't make any sense, don't rule out a problem with the test equipment. Do you have another vehicle on which you can confirm the gauges read properly?

Years ago on another vehicle, I tore my hair out troubleshooting a seemingly defective compressor. After the careful use of professional grade foul language, I found the test set couplings were not making a reliable connection. When initially connected, they got a valid reading, but that was only as I squeezed on the couplings. When I took my hands off, the couplings backed off just enough to disconnect from the lines, but still appeared connected. The gauges showed what was trapped in the test set, not in the actual system.

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I reread your intial post. A couple things. Is 400 grams of refrigerant the total amount in the system. If so i believe on a 4.2 liter the amount should be 750 grams or 1lb 11ozs. Do you still have the a/c sticker on the car. Your pressure readings would be about right if only half charged. You have an 03 4.2. I have an 06 4.2 supercharged. From what i have read the supercharger does not change a/c volume. My sticker says 750 grams. If yours says 400 then disregard my theory. Did the compressor get weak or blow up. Either way a new condensor or at least a new dessicant/filter sack is recommended

 

Hi sorry for late reply
Been very busy at work
Yes I did the paint line test three times to make sure
Every time the lines were all most lined up
Probably the thickness of a a4 printer paper
Power draw at clutch coil was 3.1 amps

Car dose not have sluggish power steering when turning wheel
supertime belt is nice and snug
Thanking you

 

Hi sometimes I wish it was
But no its the 4.2

 

Hi thanks
Will read
Have a new condenser and bag new ac compressor fitted
had the lines flushed out as well

 

Thanks
I get confused on what year vehicle is some say 03 vehicle Rego says 04
Vin is HM90145
system was vacuum drawerd and left for around 30 hours
was all good held negative vacuum
ac stickler says charge weight 750g+50g (1lb11oz+2oz)
so from a empty system I managed to only get 400g into system ac compressor clutch Engaged but system won't expect any more 134a refrigerant
Have installed new condensor and bag new ac compressor
new o rings
Lines were flushed
Thanking you

 

Sounds like you replaced all important parts and should be good to go. But why you cant get the full charge in is a mystery. Without the full charge it will never cool properly. The weird thing is that your pressures at half charge are about right. Are you positive the compressor is engaged. No offense intended. Member aarcuda is well versed in a/c as well as karl and others. Maybe someone can shed some light as i am out of knowledge

 

hi no offense taken
Yes compressor is definitely engaged you can hear it click on as well as see the clutch spinning
When turn off ac clutch stops

 

well then. One last thought. Have you tried putting the refrigerant can in a bowl of hot water while charging. Right side up and gas only. It helps give the gas a pressure boost. It is an old hack that i have used with success just last year. The only thing else i can think of is the piston/valve on the rear of the compressor is in bypass mode. Kinda stumped my friend

 

Yeah, I'm kinda stumped, too.

An important point was mentioned, that you've only got about half the required charge of refrigerant. No idea why it won't take more, even if the new compressor was bad or on the very slim chance the expansion valve was stuck open.

Definitely try the warm water trick to help persuade the refrigerant out of the can and into the system. Make sure the manifold set is making a good connection. See my previous comments about the couplings physically locking on but not properly depressing the little plungers.
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What were the symptoms that led you to replace the compressor? Was there at least partial cooling or a somewhat normal pressure differential between the high and low sides? If so, It's extremely (edit) unlikely the expansion valve suddenly stuck open, in addition to whatever fault previously existed (and may still be there).

It may be worthwhile to let a professional take a look. Long distance troubleshooting doesn't always work out.

 

good call on the coupler possibility. I have had that before myself. Takes only a breath to show pressure but more to inject the gas. Thinking cap on full there Karl