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Redoing the system, do I need a VOV, other ?s

baluvandor on Mon July 12, 2010 2:03 PM User is offline

Year: 1984
Make: Volvo
Model: 240
Engine Size: 2.3
Refrigerant Type: R134a
Ambient Temp: 90
Country of Origin: United States


My first post here...

I have a 1984 Volvo 240 wagon that came to me with a seized York compressor. I want to convert this car to the rotary compressor that came in the '85 and later models and of course also to R134a.
I have all new hoses, I bought a parallel flow condenser; I have a 134a conversion kit from Volvo with some ester oil, an evaporator, a drier, the filler fitting, lots of goo for the hoses, some control valve with a tube attached (I assume that is the bulb thing that goes between the fins of the evaporator); and I just ordered the generic compressor from ACKits.
I have tinkered with cars for almost 20 years, including extensive projects like replacing engines and transmission, and I do have a degree in mechanical engineering, but I have not messed much with AC, so I hope that you all can enlighten me. I am planning on doing all the installation work myself and then taking the car to a shop for them to draw a vacuum and then fill the system.

My questions:
- do I need a new evaporator? I am confused as to why Volvo would include one in the kit. Unless it is a higher efficiency or bigger model? I would really prefer not to have to replace it...
- Someone on a car forum suggested a VOV, but reading up on it on this forum most people do not have a positive opinion of them. My priority is to have a decent system with maximum reliability. I am willing to sacrifice some performance for reliability.
- Where is the orifice valve located usually? I assume if I don't install a VOV, I can just reuse the old one, e.g. it is not something that wears out, right?
- I assume the compressor I ordered is dry. Does it matter if I fill it with the oil before installation or if the shop adds it when they charge the system?
- any other pointers for an AC newbie doing this kind of installation?

Balazs in Fort Lauderdale
(I am dying without AC!)

Riptides99 on Tue July 13, 2010 5:22 PM User is offline

I'm new to these boards but figured I would try to answer some of your questions in a general sense.

Firstly I've spent over a year researching automotive A/C repair from a DIY perspective, repairing my own was not something I just jumped into doing as a weekend project, and many of the questions you have, I had as well and was able to answer them through researching. No two cars, systems, are alike and it's hard to answer specifically about any one car, especially lacking the proper documentation for that vehicles A/C system.

Where the evap is concerned you may need to go ahead and pull the old one and thoroughly inspect, both for differences in the old and new, and for leaks in the old. If they included a replacement in the kit there has to be a reason. Either the old unit is prone to systemic failure, or there is a difference where retrofitting is concerned. I'm at the end leg of my install and have run into the same problem, there being 2 different styles available for my car and can find no documented reason for this.

A VOV, variable orifice valve, is application specific as far as I am aware. If the old system used it, best to replace it with a new like same, if it doesn't call for it, then it's probably not needed. But that's from what I've read, and may or may not apply to your situation.

You should always replace the orifice valve with a new one. It consists of a pressure regulating nozzle preceded by a debris screen, this is usually one of the cheapest parts that can be replaced. Most times it's going to be in the liquid line coming from the condenser, this is usually discovered by the "dimples" in the line which are there to hold it in place. Depending on the type of liquid line you have sometimes it can be removed and replaced, but being a Volvo design, most likely the entire line will need to be replaced as it's not serviceable. I've seen extremely few cases where these can be cleaned and reused. All shop manuals suggest replacing as well.

A compressor will never arrive "dry". It will have some type of fluid in it, sometimes the documentation with the compressor will specify the oil inside, other times it may not. You should always thoroughly bench flush the new compressor with the type of oil your going to be using in your system. The general rule is to drain and measure the fluid in the old compressor before doing the flush then and add the same amount of new oil afterwards. If the old compressor is dry, or unavailable, then you'll have to resort to the shop manual specifications for the amount of oil to add to the compressor/system for your specific application. Too little and the compressor will burn up and fail eventually, too much and the system will bog down trying to move the oil and have reduced cooling effiency as a result. This is a very important step, calls for precision, and by the time the system is connected into the car it's much more difficult to add the proper amounts of oil to the different parts, not impossible, but just much more difficult.

The only other things I can offer is that the accumulator/dryer needs to always be replaced in any system where it's being retrofitted or exposed to the atmosphere for any amount of time. Both the evaporator and condenser need to be thoroughly flushed with the proper solvent to remove any old residual oils and possible debris lodged in them, then checked for leaks. If this cannot be done then replacement is the only other option.

If you fail to do any of this in the proper fashion and the compressor goes out, then you'll probably have to start all over again with replacing the compressor, orifice valve(line), and accumulator/dryer assembly, along with re-flushing the system from the contamination of the system from the failed compressor. So it's a line between doing all this yourself or having a shop properly retrofit your vehicles A/C system, as a shop will usually warranty it's work, whereas if you do it all, and it fails, you're out of pocket for both the parts and your labor.

bohica2xo on Wed July 14, 2010 3:25 AM User is offline

Ah, another Brick kit.

To save a bunch of typing, I will post a link to the last thread we did on this:

Volvo 240 retrofit kits

I would not put a VOV anyplace but the trash can. If you want a variable orifice, install a TXV.

Once you work your way through the ramblings of the old thread, hit us with your questions.


"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.

ice-n-tropics on Wed July 14, 2010 10:17 AM User is offline

From under the car, I asked a BSME to hand me a 3/8" ratchet. He handed me a 1/4" ratchet. ...! Good to hear from you that not all BSMEs are clueless when it comes to mechanical aptitude.
Volvo pioneered retrofit methods that were different from the industry at large.
They use Ester oil to avoid copper plating from residual R-12 with PAG and so that the sight glass can still be used for charging.
I wouldn't change the evaporator coil unless I could understand the reason from Volvo.
VOV is a piece of snot. Never used by OEMs.
One A/C theory and practical A/C installation manual is the book "How To Air Condition Your Hot Rod" from Amazon.

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

Edited: Thu July 15, 2010 at 10:26 AM by ice-n-tropics

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