A/C 134a little cooling correct pumping pressures

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Apr 14, 2018 | 04:06 PM

dive2663225

Thread Starter

5th Wheeling

Joined: Oct 2010

Posts: 48

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From: Florida

A/C 134a little cooling correct pumping pressures

Heya fellas...Summers coming Yikes its hot here!! Low side (compressor running and not cycling) 40-45 psi High side- 200-225 Psi with ambient Temp around 90....which are very close to being correct according to the charts

But when i shut the ac off...system pressures take at least 30 min to equalize....where they should do so in about 15-20 seconds (Truck off)
In 2014 I had a mishap slided down an icy hill up north and hit a pole...slowly....But condenser got punctured, I replaced the condenser...filter dryer..Both hoses and Installed a Variable orifice tube as well as pulling the compressor and draining / measuring the oil..so proper amount of oil in system.......No problem moved back to florida and a/c worked great till now
I'm thinking right away..it has to be a clogged orifice...but sort of puzzled here..if it was plugged i would be getting incorrect pressure readings..in other words..It seems to be plugged only in one direction?? can that be possible with a VOV Variable orifice tube..which i found to be great cooled better in traffic and reduced high head pressures in the heat
Getting ready to tear into it in the next day or two...
I bought old greta brand new in 1990...(heheh) only woman that ever put up with me for 26 years lol ) F250 351 windsor and when r12 was going to the black market back then i converted her to 134a I'm no professor but i learned many years ago with auto a/c, Its all or none no short cuts Massive flushing...over vacuuming..i am so **** about it i feel like a surgeon when i do a/c work The Compressor is about 6 years old..and everything has been replaced since converted evap too
Any two cents guys i would greatly appreciate

Apr 14, 2018 | 04:32 PM

bigredtruck

More Turbo

Joined: Dec 1999

Posts: 582

Likes: 5

From: New Orleans United States

I'm not sure how they work, but if that variable orifice tube closes when the compressor isn't running, and your compressor valves are holding tight, that might be normal.

Found this online:

"With a VOV at idle, a bimetal control spring blocks off one of two ports, reducing the flow of refrigerant and allowing more heat to be removed in the condenser. As speeds increase, the valve opens back up allowing maximum flow through the system again. This improves performance over a fixed orifice tube at low speeds and idle, while still providing a high level of performance at highway speeds."

Apr 14, 2018 | 05:36 PM

dive2663225

Thread Starter

5th Wheeling

Joined: Oct 2010

Posts: 48

Likes: 0

From: Florida

Thanks Red but in all the years..even before i tried the variable orifice tube....when the compressor shut down..pressures quickly balanced out the same ex. 100psi on both high and low side. after 30 sec of compressor off.
you wouldn't think a variable orifice ..could be designed to fail in the sense of completely closing off...hence blowing your compressor
usually most diagnostic to a/c the manifold gauges say a lot.....I also thought the correct pressures i was seeing maybe were false and due to plugging of the orfice tube on both ends.....So I goosed it with a bit more of 134a..and the pressures climbed as they should have
I guess a picture is worth a1000 words i will find out when i tear into it

Apr 17, 2018 | 04:02 PM

dive2663225

Thread Starter

5th Wheeling

Joined: Oct 2010

Posts: 48

Likes: 0

From: Florida

Quote:

Originally Posted by bigredtruck

Was going to tear into today,,,but feelin lousey......That adjustable has been in the truck almost 3 years...it has always acted like a strait orifice tube in the sense of shutting down the a/c with gauges on it...it would always equalise the pressure between the high side and low side within 20-30 sec AS It is suppose to do...I'm Not 100% sure BUT I do not think it is ever suppose to close off or have the ability to do so, cuz if it did with a good compressor it would pump down all the refrigerant into the condenser under high pressure Just like how you back seat a home Air conditioner condenser...You when you run the compressor it pumps refrigerant into the condenser and traps it..so you can do a repair without loosing too much refrigerant
Which is how lots of home units are pre charged with enough refrigerant to usually compliment 25-40 feet of pipe to the evaporator

Apr 18, 2018 | 02:20 AM

Da_Lariat_Chariot

Laughing Gas

Joined: Feb 2015

Posts: 765

Likes: 1

Ditch the variable orifice. I got less that ideal performance when I tried it one. Stick with the fixed BLUE orifice, preferably Motorcraft.
https://www.ford-trucks.com/forums/1...-98-4-8-a.html
I linked this write up I did while ago where you can install a few add ons to squeeze better performance out of a converted R-134a set up. Ford put out this TSB awhile back when people were complaining about the new refrigerant not performing to their good ol' R12 set ups. Basically, assuming you have an updated R-134A system you will benefit from the upgrades in the link, including: 7 blade fan, heavier duty clutch, a 1995 model year condenser, install air deflectors, wrap the accumulator, and I also put on a heater bypass valve to keep hot coolant away from the evap core. But in all seriousness the problem is most likely the variable orifice.

Apr 18, 2018 | 07:43 AM

jas88

Lead Driver

Joined: Feb 2002

Posts: 7,961

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From: Greater Austin, Texas

I agree with DLC, I also tried one of those VOVs in my Bronco years ago and was not satisfied. It seemed to work good sometimes, and sometimes not. However, I recommend using the RED tube for 134a. BLUE tube is for R12.

Apr 18, 2018 | 08:08 AM

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,786

Likes: 1,751

From: Kentucky

Quote:

Originally Posted by jas88

I recommend using the RED tube for 134a. BLUE tube is for R12.

X2......

Unfortunately you need to evacuate the system to see what is going on. If you feel the VOV was working okay until recently, obviously something happened internally. They only way to find objective evidence is opening up the system and inspecting the orifice tube for debris or other damage.

We can all state our opinions on red/blue/VOV orifice tubes, like we already did!, but until you open this thing up it's pure speculation.