Can We Find a Competent AC Tech in Karachi?

[pwuser162557941033]

I understand. Yes, a cheap part of dubious origin even if new is subject to potentially crap mfg and QC. But is an old used scrapyard compressor stored with the ports open, old oil, and significant contamination much better just because it's Japanese?

I'm still communicating with him, says that his experience working on cranes/excavators means my car is a "biscuit" by comparison - great! Fix my biscuit, please. But at least charge by weight and use a vacuum pump. He's adamant he doesn't need to do these things and that the Chinese comp will give out.

[Xulfiqar]

I am a but okdschool and actually open up such items to inspect and refresh them before putting into service.

With scrapyard item I open it up to see whats up inside.

Do something first
Connect a manifold and check the running system pressure ar idle and at fast idle to get a base point.

[pwuser162557941033]

Would you expect Sabir to tear down and inspect a compressor? I could just visit him tomorrow and hand the car and the TXV over to him, give him a blank check to get my system nice and cool at idle no matter the cost. There's inevitably some excuse or something to blame when they don't succeed at doing the job correctly, though.

Or I could buy a pump and practice vacuuming my current AC system and recharging by weight, see if it improves performance at all.

Then later try and take a gamble, install the Chinese compressor, install the new TXV, do the procedure again.

It's just so much money and time wasted.

[pwuser162557941033]

Connect a manifold and check the running system pressure ar idle and at fast idle to get a base point.

Low/high sides:
1000rpm: 26/130 psi
3000rpm: 18/160 psi.

[Xulfiqar]

You are severely undercharged here,

18 psi on the suction side means you are close to 20f which means your evaporator core is at -6 to about -10

Which also means it will be a literal block of ice, but as we can see your liquid side is a piss poor 130 psi, you are not even getting remotely close to capacity.

What you probably have is a wide open txv due to starvation or wrong install, if everything is okayish the “thandaa” you experience is just air blowing over a partially frosted evaporator (if should not be frosted but actually sweating - meaning it should be above 0c/32f meaning 30-35 psi, closed off fresh air should force the system to cool off and the thermostatic bellows should cycle it off.

First things first, diy a fresh gas charge with using a kitchen scales to gauge the amount of refrigerant in the small can you buy, that will be a starting point here.

Do mention how cold is the suction line when at fast idle? Painfully cold and sweating?

[pwuser162557941033]

There's an NTC probe attached to the suction line at the end of the evaporator coil inside the cabin. It reads 24C glancing at it in traffic at 1000rpm. At 3k+ RPM it reads 15C. The evap isn't frozen at all, I'll double check it for you right now and show the NTC reading too. The suction line sweats at the evap and where it attaches to the compressor port.

When I tried charging it slowly through the low side suspecting undercharge it wouldn't go above 160psi at fast idle for ten minutes of charging and observing.

The TXV also hisses on and off, suggesting it's doing some metering.

[Xulfiqar]

Your evap is at 24c with a 16 psi suction?

[pwuser162557941033]

At 1k rpm idle, 18 psi suction, 20 celsius on the NTC at the end of the evaporator coil. I'll go out to the car and confirm the evap temp and inspect more closely whether it's freezing, probe with a K type if necessary.

[Xulfiqar]

You are either severely undercharged or your txv has decided its a tuba.

[pwuser162557941033]

Got it. Just got in and started the AC at blower speed 2.

Ambient is 32C.

Took 3 minutes to get to 18C, TXV started hissing quietly at that temp. Revving it to 3kRPM it got to 13C, 1kRPM it quickly goes back to 20C within seconds.

Evap is sweating all over, mildly cool to the touch but definitely not freezing or iced over.

[pwuser162557941033]

your txv has decided its a tuba.

First things first, diy a fresh gas charge with using a kitchen scales to gauge the amount of refrigerant in the small can you buy, that will be a starting point here.

Alright, how does this sound? Buy a cheap vac, replace the TXV, vacuum both sides of the system for 90 minutes, charge refrigerant by weight.

[Xulfiqar]

Can you inspect the txv while in place? Is it attached properly?

[pwuser162557941033]

Here's someone else's evap:

What should I be looking for?

[pwuser162557941033]

I can see it. Here's the TXV.

Also, the sight glass on the drier is clear, with the occasional bubble visible. Another sign it might not be undercharged.

Sabir's showing me his collection of 110V vacuum pumps and Chinese digital manifolds. "Jab itni bareeki main banda kaam kar raha hay toh vacuum pump ki kya auqaat hay."

Might as well pay him a visit and see if he's willing to work on my car. He insists that a sight glass negates the need for a weighing scale, "khud bataye ga usko gas ki kitni need hay."

It seems he once perhaps did things by the book, as you've mentioned in the past, but has come to disregard proper procedures in favor of his andaaza. Cutting corners, like anyone else. But he agreed to look at my car and let me know if he's willing to work on it.

[kameetaha]

That's like refrigerator's TXV. Same type of valve is what you find in LC100s center cool box.

[Xulfiqar]

I think I see a problem

Assuming the valve thermal sensor tube orientation is upwards (relative to the car - aka the case is opened horizontal.

The txv sensor bulb seems be attached to the lower side of the tube (disappears into the cork tape)

The sensor bulb needs to sense the vapor side which is upper and be firmly attached to the clean polished tube with a clamp and maybe helped with a drop of thermal heatsink paste too (if feeling fancy)

Basic rule for attaching the txv is that its sensor is placed at 10-11 o clock orientation of an imaginary cross section of the tube (dependant on the actual vertical not box vertical as it maybe installed different)

[pwuser162557941033]

Excellent, that's very visual and helpful, I think I got it. 11 o'clock position with 12 being real world "up" from the pov of the cross section of the tube. Thank you. You're saying it seems to be in the 9 o'clock position in my picture?

Perhaps I should start with just cleaning the area, reattaching the bulb, wrapping it in butyl tape (that's what I have) and orienting it that way? I have some thermal adhesive I can use that can cure solid in a bulbous shape around the bulb and the contact surface of the tube.

I'll post the Denso guide here that came with the TXV. It mentions to place the sensing bulb in an indent in the tube, which may or may not exist under the cork tape.

[Xulfiqar]

The bulb should be fastened to the tube firmly with its clip or with a screw clamp if you have lost the clip

Shine up the sensor bulb gently (dont overheat it badly) and the evap tube (should have a depression to house it if its genuine)

Place it proper (it seems like its at 7 or 6 o clock - which will never work) either 10-11 or 1-2 o clock then wrap the cork tape again, you can do a manual test too, use a cup of ice water to simulate temperature and see if the txv responds. Imagine it like the sensor is a balance valve to keep the refrigerant at boilover spec and keep the evap a hair above freezing so you dont freeze humidity on it. Its supposed to condense and drain out.

You also need to make sure the txv is correct for your application. They are not the same as most ac shops will tell you.

[pwuser162557941033]

Visited Sabir.

Asked him for the TXV adjustment, he had one of his guys clean the tube and sensing bulb with petrol, seat the bulb correctly in the indentation on the evap, secure it with a worm gear clamp, wrap it with Everseal tape. It wasn't making proper contact before and the clamp used to secure it had come loose.

Temps have dropped 2°C across the board, 18°C at idle and 13°C at fast idle. I observed 4°C on occasion while driving at night, which I did before also, but it seems to reach that temp faster now.

I spent a good six hours with Sabir and he had a lot to say and a lot of stories, but he doesn't vacuum any customer vehicles, doesn't charge by weight, and cuts corners like anyone else.

Admitted to doing this because "return nahi hay." Which is true, and I wrote as much earlier in this thread. He's comfortable servicing his corporate fleets and construction equipment contracts and wants to wrap up the AC business because of the flood of counterfeits and a lack of equipment, parts and real paying customers.

[Xulfiqar]

Its the same location but has taken over the gym too.

Good that you got some advancement, as I suspected the txv sensing bulb was wrongly installed as your posts told of an overfeeding txv symptom. But diagnosing over the web is hit or miss.

Anyway,

Now see that your compressor pumps up a solid head pressure or not, the txv is the variable choke point which is now functioning so your liquid pressure should be nice and high now.

I would also suggest to insulate the suction side thats near the exhaust manifold to keep it from the scorching heat (ala old bmw shtyle because their design is a bit wild, or old land cruiser style coz their design is half baked) - it helps keeping the compressor cool and ups system performance.