Year: 68
Make: Chevrolet
Model: Camaro
Engine Size: 350
Refrigerant Type: R134a
Ambient Temp: 100
Pressure Low: 100
Pressure High: 150
Problems when charging newly assembled Vintage Air system (expansion valve, Sanden compressor). New to this type of work. Pulled good vacuum for 60 minutes and held prior to attempted charge. When can charging, very high low side pressures (80-110). First introduced R134 from low side only, engine off. No xfer to high side. Opened high side valve and pressure rose on high side. Warmed can, tilted side to side, Closed high side valve, started engine and compressor engaged. Kept charging and low side rose to approx 120 after 1.5 cans (18 oz.) high side 150-160. Closed low side valve. Low side gradually lowered to only 90. High side did not change. Raised RPM to 2000 RPM for about 5 minutes, no change in readings. Good airflow across condenser. Bubbles in sight glass. I know I need to add more 134 (Vintage Air calls for 1.8 lbs or 28 oz) but don't want to waste refrigerant if system is inop. Vintage Air specs call for only 6-12 psi low and 160-250 psi high. Turned engine off, static pressures equalized at approx 70 after 15 minutes or so.
Vintage Air system is new old stock (1995 ) never previously installed. Tube and fin condenser.
Should I proceed trying to get more refrigerant in system? Very concerned with low side pressure being so high. Stuck open expansion valve? Or is what I'm seeing normal when charging a system for first time? Will low side pressures be high when charge is low? Banging head here.....
I'd be looking at the TXV. 15 minutes to equalize seems too long. Remove TXV sesing bulb. Place it in hot and cold water. See if it changes the pressures.
Exceptionally difficult to get to without removing evaporator case from car... Off to garage I go to try....
Looks like I'll need to remove evaporator assembly to service or check the expansion valve. Added more refrigerant to try to get closer to recommended charge (just couldn't help myself). New numbers..
While charging at idle
130 high
130 low (later edit for clarity. 130 low was while hand wheel was open and charging in progress. Low side dropped to 100 after closing hand wheel and shutting of can valve.
No change at 2000 rpm
Static immediately after shutdown
100 high
130 low
Static 5 minutes after shutdown
90 high
125 low
While charging, top of condenser was too hot to touch while bottom half of condenser and hard-line to receiver/drier was room temperature. Seems normal.
Expansion valve was cool-to-cold to touch while discharge side of valve was warmer.
Edited: Tue July 05, 2011 at 9:34 AM by Qwkretrofit
the smaller tubing should be warmer than the larger tubing. You state that while charging, the low side is 130 and high side is 100. When you check this, are both handwheels closed? If yes, you most likely have a plugged/restricted TXV. TXV sesing tube should be insulated and mounted at the 2 to 4 o'clock position on the output tubing (larger) of the evap.
Retro,
What is the louver air temp and suction line temp?
maybe your suction pressure gage is out of calibration.
hotrodac
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Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod
You start out 30% undercharged, and wonder why your pressures are not to spec? Get the full charge in it for evaluation.
Are both handwheels closed on the manifold while you are testing?
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
Just got off phone with Vintage Air Tech. He suggests compressor may be an issue. Discharge system, remove compressor connections, manually turn over compressor and check for strong vacuum on suction side...
Certainly easier to get at the compressor to check it for suction - I wonder if Vintage has seen this issue before with that compressor?
With a new system from a box you don't generally expect a bad compressor, or a TXV for that matter.
With those kind of pressures, your compressor could have a leaking suction valve. I do still wonder why you have a static pressure of only70 psi - on a 100f ambient day under the hood of a vehicle that had been running 15 minutes earlier. Those numbers just don't add up.
Are you very sure that the connectors are properly depressing the service port valves? The low side schrader can act like a check valve with a very high cracking pressure if it it not depressed. You can have an actual low side pressure of 15 psi, and be reading 75 psi. The very slow equalization to an impossible number is also a sign of this.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
Put your gauges on the vehicle. Turn a/c on. Take a pair of pliers and crimp the suction line for a few seconds. If the compressor is working. It will pull into a vacuum. No need to discharge the system.
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That ChinaMart gauge could lock up solid - and still not depress the schrader valve properly.
To have 70 psi with 134a in a system, you would need an ambient temp about half of what you are at - without adding the underhood heat.
Most likely nothing wrong with your system. Those gauge sets are great stuff for chocking a wheel while jacking up a car for an oil change.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
We use vice grip pliers here. But you only do it for just a few seconds!!!! All you want to do is se if the compressor is pulling into a vacuum.
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Going backwards now. Harbor Freight low side adapter totally fubarred the shrader valve pin. Ended up breaking the pin off trying to straighten it hoping that I would be able to get the low side adapter to work.. All my previous readings on the low side are extremely suspect. As bohica2xo recently posted, there is a possibility that nothing is wrong with my system, I was just unable to get a charge in through the fubarred shrader valve, and was reading pressure just off of what I had crammed in the line up to the adapter fitting. Makes sense to me. Since I didn't disconnect between my vacuum job and the charge, my vac job is suspect too. Better to start all over. Could it be that simple? I'll get a new shrader valve and beg or borrow a quality gauge set and try this all again tomorrow night...
I need a "bang head" emoticon....
Edited: Thu July 07, 2011 at 9:59 AM by Qwkretrofit
Buy yourself a decent gauge set. 90 Bucks.
DIY Gauge set
A good gauge set is necessary for A/C work.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
Interesting turn of events. While chasing down the shrader valve/faulty coupler problem, I discovered that the low side fitting had a weld bubble in the bottom of the fitting preventing the shrader valve from opening when depressed. The valve would install, seat and hold pressure but would not allow the pin to be pressed with the quick coupler on the gauge set. That's what was causing the pin to bend when installing the quick coupler on the gauge set. This morning I made up a new hose section with a different hose end and low side fitting, and am presently vacuuming the system down... I'll return and edit this post if the charge is successful.
Later edit: System charged and operating normally. Hi 30's from center vent. Weather change here though (Rain and 85 degrees) so I couldn't check how it does in our normal 110+ summer weather. High side pressure went up to 325 while testing in garage though... (100+ ambient, very high humidity) Not enough airflow over condenser I suspect. Looking into an electric fan to rectify that.
So a simple quality defect on the fitting weld job had me chasing my tail over the last weekend rather than moving on to my next project. Ahh well, such is life.
Thanks for the help!
Edited: Sat July 09, 2011 at 1:55 AM by Qwkretrofit
Looks like all is well after running it a couple of days.
At 1500 rpm, 100 degrees ambient, 188 water temp, clutch fan engaged. High side 265 low side 10. Center vent 35 degrees. I do have condensation and very cold temps on the suction line where it connects to the compressor though.
I need to shroud my fan and I'm looking into a supplemental electrical fan or a more efficient parallel condenser. The compressor kicks off and on after a prolonged idle. Due to high pressure I suspect.
Edited: Mon July 11, 2011 at 9:31 AM by Qwkretrofit
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