*FIXED**dying comp, cooling fan replaced* Old Delphi CVC-125 variable comp (TXV system) exhibiting a strange behaviour

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Re: Old Delphi CVC-125 variable comp (TXV system) exhibiting a strange behaviour

Postby Al9 » Thu Aug 06, 2020 8:11 am

Ok guys. Story goes on.

Car is in the shop getting the compressor replaced. The old one has its original pulley bearing still able to rotate smoothly and quietly even though we are at about 73000 miles and the clutch assembly had been fiddled with 3 times to replace failed clutch coils. Old compressor is out of the car by now. Rotating its clutch hub by hand creates a loud intermittent "rusty door" kind of noise (worn pistons?).
Most notably, the car had a worn belt tensioner that was unable to function properly and both the water pump pulley and the AC pulley had some rubber on them, but curiously enough i never heard any audible belt squeal at all in its whole life. Hot or cold, AC on or not, blower fan on top notch and all lights on, revved or idle... never any strange noise at all from down there except the "Howie scream" kind of noise the old compressor created when revved up with a hot engine in hot weather.

New compressor fitted. Chinese replacement, looking like UAC CO 11068LC. System still had the correct refrigerant charge weight inside. System received a closed loop R-134A flush as per compressor installation instruction sheet. Evaporator has been connected to the rest of the piping through a Denso 447500-1600 TXV (which had the metering pin and its spring removed to prevent it from closing up) during the flush and after it was done, it was replaced with a second hand replacement system TXV in mint condition. A second hand hose set (flushed by myself with quick drying electrical contact cleaner) has been fitted in place of the old one too, new hoses don't seem to be blocked/delaminated. New receiver dryer. New seals. The system charge of 5 fl oz of double end capped PAG 46 (local commercial brand; TSI Supercool PAGs could possibly be an example of an US equivalent product) has been poured into the compressor's oil drain hole, then the compressor has been held for 1 minute with the clutch facing the ground in order to lubricate the shaft seal and then the clutch hub has been rotated 10 times to lubricate the remainder of the compressor. After charging with refrigerant (Done with the compressor not engaged, through an RRR station, by weight), the oil has been circulated around and the new compressor has been ran in by letting AC run with the engine idle and the cabin blower fan on maximum speed for 5 minutes straight.

1)Cooling action is now immediate after turning AC on. No more "warm-up" period. Engine cold or warm or hot, turn AC on and cold air immediately starts flowing from the vents. 95F 40% RH weather.
2)More engine load than before while driving, again 95F 40% RH weather.
3)At idle, compressor is whisper quiet from the outside with hood open. And it was tested inside the shop. The only way to tell it's engaged is to notice the condenser fan running and the AC clutch hub rotating. Gets completely drowned by the engine and the rest of the accessories pulleys rotating. Rev it up and the groaning noise appears though it's really quiet now. Seems to be weather related and noisier when the system is correctly charged.
4)Vent temperature is now stable, whether driving or stationary. Comfortably cold but not hanging meat cold due to the red 44 psi control valve the new comp came with. Not measured it yet but has to be about 43-44 F (old one with the blue 42 psi valve went as down as 41F while it was still in good condition), full recirc. Looking to replace the CV with a brown 43 psi or blue 42 psi one in the next future. Possibly next year if the virus thing abates and i can get another one shipped.
5)Suction line is now sweating (but not freezing) all the way to the compressor.
6)Inside the car, the new compressor is still making the same groaning/Howie scream noise the old one made whether idle or driving. Perhaps all CVC/CSV compressors are like that by design (new compressor, proper oil charge and type, proper refrigerant charge, good hoses, new muffler, new condenser, new TXV, at this point it's just normal compressor noise). Not oil related since the system now has the 5 fl oz oil charge inside without a doubt, and the DEC PAG 46 mixes with the R134A like there's no tomorrow btw. Will see if colder weather/correct control valve fixes that for good. On the new hose/line set i also put a little rubber ring where the suction line encounters its clip in order to make it truly pothole-proof (LOTS of potholes around), and this could be another possible reason for the noise (replaced clip previously and for some reason the replacement one is larger than the suction line; just filled the gap and it slid in perfectly).
7)TXV removed from my car looks shiny clean. Other TXVs i bought all look badly burned/inlet encrusted in black sludge. But this one had only clean PAG oil inside. No signs of dirt anywhere. The only remark is that its shaft looks a little bent for some reason (replacement TXV has a thicker shaft sheathed in black resin where it meets the suction line likely to prevent this). But it's still fully opening and partway closing like it's supposed to do, and exactly like the one currently inside did when tested. Didn't lose any spring tension.

All in all, i guess my compressor eventually got a little too old and worn.

EDIT 28 Sept 2020: Found out the cooling fan electric motor was severely worn out as well. Replaced the cooling fan assembly with a new one, and now compressor noise is totally non-existent at any engine temperature condition. Now all that can be heard from the TXV area under the dashboard is a steady squirting noise; looking to try to eliminate this by replacing the turbulent flow factory TGK expansion valve with a laminar flow silencer-equipped Denso one in the near future.
Posts: 223
Joined: Tue Mar 10, 2020 3:26 am
Location: Southern Europe

Re: *FIXED**dying comp, cooling fan replaced* Old Delphi CVC-125 variable comp (TXV system) exhibiting a strange behavio

Postby Al9 » Sun Oct 18, 2020 3:45 am

For anyone interested in the bubbling noise i experienced, according to this Denso patent https://patents.google.com/patent/JP2006200844A/en, it seems like it's entirely normal occurrence at low heat loads due to the TXV filling the evaporator up with a turbulent liquid refrigerant+oil flow while simultaneously reducing flow rate. And that explains why it tends to go away once the ambient temperature and relative humidity (=evap heat load) rises up (refrigerant flow rate increases and flow apparently "smoothens out" as a result). Also makes sense that, in mild climate, as soon as the radiator fan starts running the noise either begins or gets prominent, this has to be the additional airflow dropping the head pressure and decreasing refrigerant flow rate. Curious as to whether this reasoning also applies to a low refrigerant charge induced low flow rate condition as well. No flow restrictor on my TXV's inlet, simply a noisy TXV and evaporator design and nothing else.

On my car, the block TXV is horizontally mounted level with the evaporator inlet (evap is kept vertical inside its housing). No intermediate piping between the TXV and the evaporator, it's mounted straight on the evap's flange. Evaporator passages are arranged so that the refrigerant travels upwards as soon as it gets sprayed inside.

Bottom line, the bubbling noise seems to be nothing to worry about as long as the system is performing well. Actually decreased in magnitude and now a barely hearable "squirt" even when running the system on a 50F cold morning with a hot engine, after the faulty radiator fan assembly got replaced with a brand new one.

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