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vintage air, high low pressures when charging Pages: 12

Qwkretrofit on Mon July 04, 2011 3:11 PM User is offline

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.....

Dougflas on Mon July 04, 2011 3:55 PM User is offline

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.

TRB on Mon July 04, 2011 4:02 PM User is offlineView users profile

Quote
Originally posted by: Dougflas
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.

Is it even attached correctly?



-------------------------
When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

Qwkretrofit on Mon July 04, 2011 4:22 PM User is offline

Exceptionally difficult to get to without removing evaporator case from car... Off to garage I go to try....

Qwkretrofit on Mon July 04, 2011 5:52 PM User is offline

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

Dougflas on Mon July 04, 2011 8:25 PM User is offline

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.

ice-n-tropics on Mon July 04, 2011 8:30 PM User is offline

Retro,
What is the louver air temp and suction line temp?
maybe your suction pressure gage is out of calibration.
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

bohica2xo on Mon July 04, 2011 8:50 PM User is offline

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.

-------------------------
"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.

Qwkretrofit on Tue July 05, 2011 9:19 AM User is offline

Quote
Originally posted by: Dougflas
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.

Thanks for the reply. While charging it was 130/130 with low side hand wheel open. When closed, low side went down to 100. Larger tubing is not cooler than small tubing at TXV.

Qwkretrofit on Tue July 05, 2011 9:22 AM User is offline

Quote
Originally posted by: ice-n-tropics
Retro,

What is the louver air temp and suction line temp?

maybe your suction pressure gage is out of calibration.

hotrodac

Had not gotten to louver temp yet (not cold though), and don't have measurement for suction line. I'm a garage project weekend warrior so I will return with more data starting on Friday. Thanks for the reply.

Qwkretrofit on Tue July 05, 2011 9:56 AM User is offline

Quote
Originally posted by: bohica2xo
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.

Therein lies the problem. I was trying to get a full initial charge on my new system but saw what I believed to be excessive low side pressure and the system would not take any more refrigerant.
Yes, the hand wheels were closed while testing. (I edited my second data post above for clarity. thanks)

Thanks for all the responses, I am really surprised at the volume and quality of replies, especially on a holiday. Please keep your ideas and suggestions coming. I'll post again on Friday when I have more data but from what I've learned here and the Vintage Air site, it looks like I"ll be dropping the evaporator to R2 the TXV. Didn't expect that on a new (but in the box and on the shelf for a VERY long time) system...

Qwkretrofit on Tue July 05, 2011 12:14 PM User is offline

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...

bohica2xo on Tue July 05, 2011 1:02 PM User is offline

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.

-------------------------
"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.

TRB on Tue July 05, 2011 1:12 PM User is offlineView users profile

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.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

Qwkretrofit on Tue July 05, 2011 1:39 PM User is offline

Quote
Originally posted by: bohica2xo

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.
Thanks for the reply.

I got higher statics later when I added more refrigerant. (18 oz is all it would take with low side pressures so high) 5 minutes after shut down static was 125 low, 90 high.... bass ackwards huh?

Interesting note on the gauge connection.... I'm using a Harbor freight set. On the low side, the connector snapped in place and locked in place real well when tightened. On the high side, it snapped in place easily but when tightened fully, the connector could still rock back and forth a little unlike the other connector.... hmmmmm.....



Edited: Tue July 05, 2011 at 1:41 PM by Qwkretrofit

Qwkretrofit on Tue July 05, 2011 1:40 PM User is offline

Quote
Originally posted by: TRB
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.

Thanks, I'll try that tonight...

bohica2xo on Tue July 05, 2011 1:59 PM User is offline

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.

-------------------------
"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.

Qwkretrofit on Tue July 05, 2011 3:07 PM User is offline

Quote
Originally posted by: bohica2xo
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.

Note taken on procuring a quality gauge set...
I just popped my head under the hood while at work to take a peek at shrader valves and such and I noticed the suction hose is rock hard... Think of an 18 year old overdosing on viagra..... Ambient temp of approx 90 degrees, car in shade, engine cold. I'm not sure I want to try to clamp that down to check the compressor.... May need a really large vise....

TRB on Tue July 05, 2011 3:11 PM User is offlineView users profile

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.

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

Qwkretrofit on Thu July 07, 2011 2:21 AM User is offline

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

bohica2xo on Thu July 07, 2011 8:02 AM User is offline

Buy yourself a decent gauge set. 90 Bucks.

DIY Gauge set

A good gauge set is necessary for A/C work.

B.

-------------------------
"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.

Qwkretrofit on Fri July 08, 2011 6:17 PM User is offline

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

Qwkretrofit on Sun July 10, 2011 8:43 PM User is offline

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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