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acting like a blocked expansion valve

7502yuma on Tue March 18, 2014 11:51 PM User is offline

Year: 1969
Make: Chevrolet
Model: Camaro
Engine Size: 350
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 50-100
Pressure High: 200-350
Country of Origin: United States

Hello All,
I have an interesting problem on a somewhat unique system. The vehicle has a recently rebuilt motor, custom shroud and electric fan. A serpentine system from a early 90's Buick. New compressor, parallel flow condenser from vintage air, new drier, trinary switch,new lines and the original evaporator (which I flushed thoroughly). I got the car after the customer had a motor rebuild. It had some issues, control cables were shot among other things. I have replaced the compressor,since it leaked, the lines were fabbed up locally so that I could attach them to the R4 compressorwith an aftermarket manifold connection. I did not put a muffler in the suction line and I hope that this is not contributing to my problem. The POA valve was leaking also so I replaced it with a POA delete . I also added 8 oz of PAG.
So I do my usual leak check and charge the system with about 26 oz. Then the compressor starts slipping and I notice that the pressure was going high enough to trip the trinary. the pressure bleeds off until the clutch engages driving the pressure up and the whole process starts again. So I figure a blocked expansion valve. I evacuate the system, and while I'm removing oil return line the oil shoots out about an oz or 2. I thought that was kind of strange at the time but removed the expansion valve (just installed) and put in another. They were both 4 Seasons I think from O'Reillys. I begin charging the system and only get about 12 oz in when it starts the high pressure cycle again. So I'm thinking what else could cause this and I remembered the oil shooting out of the expansion valve capillary line and think. Stuck POA! Well I contact the seller and they tell me the POA eliminator is just a straight tube with a pressure switch. So much for that idea. The seller said that they have been getting alot of high pressure complaints and they have seen alot of the offshore valves causing this. He gave me a recommendation of buying a OEM Eaton expansion valve for $80. It doesn't seem right that it would plug up that fast unless I had a really dirty system which I don't believe that I do since everything is new except the evaporator. I did flush it well.
So here I am not really sure where to go at this point. I'm hoping that someone may see something that I've missed. Thanks in advance for you help.

Edited: Wed March 19, 2014 at 6:54 AM by 7502yuma

7502yuma on Wed March 19, 2014 2:33 PM User is offline

Anyone?

TRB on Wed March 19, 2014 2:52 PM User is offlineView users profile

Have you sprayed water on the condenser to see if the pressures come down. Pressures listed don't look like a stuck valve to me. Looks more like you are not getting the heat load removed in the condenser.

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mk378 on Wed March 19, 2014 4:41 PM User is offline

A blockage at the TXV causes abnormally low low side pressure and lower than expected high side (with no flow, the condenser can cool off, all the refrigerant condenses at a lower pressure and sits there in the condenser and receiver-drier). So I'd say its not that.

It's also possible there is too much oil. New / rebuilt compressors often come with oil inside already.

Dougflas on Thu March 20, 2014 7:25 AM User is offline

Check the TXV by removing the sensing bulb from the suction line. Place it is cruched ice bath and run system. After a few minutes, remove sensor bulb and place in palm of your hand. You should see a pressure change if the TXV is working.

7502yuma on Thu March 20, 2014 1:59 PM User is offline

Thank you, that makes sense. Perhaps a combination of that and too much oil.

7502yuma on Thu March 20, 2014 2:08 PM User is offline

Thank you. I had thought about there being too much oil. The new compressor literature said that it had ICE xxx(can't remember exactly). But said it needed oil added. I have never been in the situation of having too much oil. Do I empty the drier and compressor measure and add x% of the required volume to aaccount for what's left in the lines and evaporator?

7502yuma on Thu March 20, 2014 2:10 PM User is offline

I will try that after verifying the correct oil charge. Thanks!

7502yuma on Fri March 21, 2014 4:22 PM User is offline

OK, so I have evacuated the system, removed the compressor, removed the drier and I'm not getting any oil out of either. I have not removed the THX valve or the POA. I removed the plug from what I suspect is the sump on the compressor and it was emty, I inverted the compressor first no oil. I also turned the compressor by hand and still no oil. Could it be trapped in the evaporator since that it the low point of the system. BTW, I am no saying there is no oil. There is a film on pretty much everything internal. I blew out the evaporator and only got a very small amout out (maybe 1/4 oz). I don't really want to do a complete flush again but perhaps I need to start from zero. I was lookig at a chart that I downloaded from rtitech.com and it said that if you replace the compressor to measure what comes out and replace that amount not to exceed 3 oz. I plan on pulling the THX valve next. Sy I do a complete flush. Since this is a hybrid system. What can I expect a good charge to be? . Thanks, and again ALL advice is appreciated!

bohica2xo on Sat March 22, 2014 12:13 PM User is offline

You never posted the results of cooling the condenser with a water mist.

Your initial post shows a system that is not removing heat. If you have 350 psi, you have 170f refrigerant.

The changeover to a CC system is less than ideal, but it should work acceptably.

POA systems incorporated a bleed line from the low point on the evaporator that fed accumulated oil back to the low side of the POA. What did you do with this line?

How are you measuring the charge added to the system?

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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.

7502yuma on Mon March 24, 2014 10:29 PM User is offline

You are correct, I did not. However your advice got me thinking. The first charge I had jumpered out the thermal switch for the fan and on the second I neglected to. That was the reason for the different results. I have since wired in the relay to engage the fan when the compressor is engaged. I also had a hunch the evaporator was fighting the heater core so i installed a temporary bypass. I charged with 2 lbs of R134 ending op with 32 degrees on the center duct low side at 30 and high side at 225. The ambient temp was 85 degrees. I thought this was a little low for the low side but given the situation (late on Saturday night) I was happy with the results. I did locate a leak at the suction line on the compressor and I'm getting a new line made currently. I'm experiencing difficulty with this particular fitting. I purchased a manifold and seal kit from Summit for the R4 compressor. I've had issues in the past getting it leak tight per my leak detector. Not a gross leak but nothing I will let out the door. That being said I have 2 concerns. First dealing with the coolant getting past the vacuum operated valve. I is a new quality valve but I think that it may be designed to pass come coolant. I've not found a definitive answer to this in my searches. I did replace all of the duct control cables and I'm sure that the door is fully closing. 've read that there are perhaps some seals that are deteriorated this allowing the heater to overcome the evaporator. BTW the center duct reading was 45 degrees after integrating the heater core back into the system. I have proposed to the owner installing a manual valve that is operated by a cable. In hindsight I had two issues. First the excess oil charge. Secondly the fan not engaged during my test after replacing the THX valve. I would appreciate input on my pressure readings although I think my charge at 2 lbs was a bit low and if anyone has insight on the heater core issue. We don't need heaters much i Yuma but its nice to have sometimes. Thanks to all that contributed to the resolution of this issue!

7502yuma on Mon March 24, 2014 10:41 PM User is offline

Bohica, To answer your other questions I left the return line as the POA delete had a fitting to accommodate this oil return line. This may be why my low side is low? Not sure how this device affects the overall system operation.

Sat March 22, 2014 10:13 AM (NEW!)



You never posted the results of cooling the condenser with a water mist.
Please see previous post. I kind of ran on.

Your initial post shows a system that is not removing heat. If you have 350 psi, you have 170f refrigerant.
The fan was not on, see last post as well

The changeover to a CC system is less than ideal, but it should work acceptably.
What do you mean by "CC system"?

POA systems incorporated a bleed line from the low point on the evaporator that fed accumulated oil back to the low side of the POA. What did you do with this line?
The POA delete had a fitting to accommodate this bleed line.

How are you measuring the charge added to the system?
I have a digital scale and man I love it. I was strictly charging by pressure when I first started out.

Jag987 on Tue March 25, 2014 1:05 AM User is offline

CC=clutch cycling.

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I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!

bohica2xo on Tue March 25, 2014 1:39 AM User is offline

Many posts on here include inadequate electric fans. You are correct, electric fans need to go to full speed as soon as the compressor clutch is engaged.

Newer electric fans are not as bad as some of the junk we used to see - when some mfgs sold a 9 amp fan claiming it could replace the 8 blade fan on a big block. I still don't trust them to get the job done in every application. If they do the job on this Camaro, then great.

The water mist is a quick test for airflow vs bad condensor issues.

Charge levels.
The electronic scale is a big help. Here is how I approach finding the correct charge for a custom TXV system. Charge the refrigerant quantity you have been using as a starting place. Begin a max load test - doors open, cabin fan on highest speed & 1500+ engine rpm. Let it stabilize for a few minutes, and record the pressures. Now, continuing to run @max load - add 2 ounces of refrigerant. Let the pressures stabilize for 1 minute. If the high side did not rise more than 3 psi, add another 2 ounces as before. On a TXV system the excess liquid refrigerant stacks up in the receiver / dryer. It is supposed to be there. The high side will have a very flat spot in the pressure curve as you fill the space in the receiver. When you add 2 ounces & the pressure jumps up 10psi or more - that is 4 ounces past optimum charge. Recover the charge, and re-charge 4 ounces less.

The oil bleed line should connect to a tiny orifice in the eliminator kit. Sadly there were kits sold that had no connection for this line & people simply plugged the line. The original POA had a low pressure check valve for this line, which allowed the oil to return to the compressor when the suction was throttled in to vacuum.

Heater valves.
A manual valve is simply a problem waiting to happen. Luckily, there is a much better valve available. For vacuum operation on GM products I use an AC Delco 155536 From the G van / P van 1990 - 1996 A good 4 port valve set up for the two GM hose sizes - shuts off the core completely. Under 15 bucks too.

CC = Cycling Clutch.

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.

7502yuma on Tue March 25, 2014 10:46 AM User is offline

That's great information. I'll save this for future use. Where do you get the Delco valve from?

bohica2xo on Tue March 25, 2014 11:12 AM User is offline

That valve is available from most auto parts suppliers. Oh Reallys, Twilight Zone, etc. should all be able to find it by number. Or as a heater valve for a 1994 GMC 2500 van...

.

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

northernbeach on Wed March 26, 2014 6:23 AM User is offline

Thank you. I will try all the rules from your post. Thanks for the sharing.

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