I want to put in the Variable Orifice Valve on my car to help improve the cooling, is it a good idea to change out the Receiver-Drier when I open up the system. My car is a 1994 940 factory 134 car, where exactly is expansion valve located, and is this something I could do myself?? Opening up the system seems easy enough, it's just on charging it back up seems a little confusing. Draining the compressor oil and adding new oil, vacuuming the system and then adding freon, is this the order it goes?? Also there is only one high/low (not to sure which) side port on my car? I've seen a lot of posts for the conversion from 12 to 134 and just want to clarify if it is different for a 134 car. Also can a person clean or see if the cooling coil is dirty and needs cleaning??

I also have the air going down to the floor under acceleration on my car, but that's a whole nother animal, I looked on the board and I think that it may be the vacuum servo motor.

If the system has been in operation for a long time, and you are opening it, a new accumulator would be a good idea (no receiver-dryer, but there is an accumulator). It isn't necessary if you are in and out, and vacuum the system for an hour or so.

I am a big fan of the Nartron VOV (Variable Orifice Valve). However, I am not convinced that the effort to drain and refill a properly-operating factory R134a system will pay off enough, unless the car is operated in the warmest of climates.

One thing about the 940, is that the R134a system works very well. The later 900 series cars had excellent ventilation systems, rather quiet, perform well even on lower settings. However, if the system charge is off somewhat, the cooling won't be good at all.

If you plan to remove the fixed orifice tube, it is located along the right side frame rail of the engine compartment, in a pipe junction that can be found (very approximately) if you were to draw a line across the engine compartment from strut tower to strut tower. It is in the smaller of the two pipes, by the way, which runs along this area of the car.

Be very careful while unbolting the straps that hold the pipe down to the frame rail. They tend to corrode, and the pipe can become extremely fragile. Some PB Blaster or other good penetrant is a good idea when opening this pipe junction.

One pitfall of opening the system is that you MUST vacuum the system out to a deep vacuum, for around an hour. R134a is very sensitive to moisture (and air) in the system, and as a result, opening the system if you plan not to vaccum it out again, will create less performance than you would have had, if you didn't touch it to begin with. Air in the system (failure to vacuum) will cause poor performance that the VOV won't make up for.

Chris

Is the receiver/drier the same thing as the accumulator. I looked on line at foreign car parts on line and they do not have a accumulator shown, they have the receiver/drier shown for around $60.00. I was assuming it was the same thing, how much is an accumulator??

If I do pull a deep vacuum on the system for an hour, will it suck out all of the oil and will I have to add all new or will just a recharge of oil work.

I do have 275, 000 miles on the car and everything works very well on the car but the a/c has been not working as well when I got it around 5 years ago. I have added and even taken some out from time to time and I just want to take all of it out and start from scratch so I know how much is in it.

Also is there a manual way to shut off the heater control valve?? Just in case it may not be closing all of the way??

Pulling a vacuum shouldn't remove that much oil, except for residual stuff in the filler pipe.

Also, the accumulator/dryer is the 'receiver-dryer', although it really isn't. It is the big can on the firewall.

I like to replace the accumulator because the later systems with PAG oil (R134a factory fill) have a lot more likelihood of picking up moisture, since PAG oil tends to do that.

The accumulator should be around $45 or so, even right at the Volvo dealer. Although, there are aftermarket ones available as well. You might get around replacing it if the system is currently charged, and you are going to pull a deep vacuum.

I was told that anytime you open the system up - it is best to replace the dryer. Opening the system allows extra moisture to get in.

Andrew in AL
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'94 940T (160K) , '92 745T (200K+)

It does not seem like you would have to replace the oil in the compressor if you are already running r134. The existing oil would be compatible with r134. I put a VOV in my car when doing the conversion so I don't know how much it helps but mine is working quite well now. I can tell you that if you install too much r134 the valve will not work well. If you change the dryer I suppose you would loose a little oil. My old one dripped out a good bit. Perhaps you can measure how much oil drains out of it. Get new o-rings for any connection you pull off.

R Duke

Always a good idea to change the filter/dryer, as one function is to absorb water vapor, which causes acids to form, thereby eating things up in there - usually the compressor seals.

The expansion valve is where the A/C hoses connect to the evaporator coil underneath the dash. It's usually covered up with black, tarry insulation.

No you can't see the evaporator coil unless you remove it from under the dash - for most cars this requires removing the dash, at least part way.

Make sure to put in the right quantity of oil. If you can't get it all in the compressor through the suction port, then put some in the filter/dryer.

Use new R134a compatible o-rings.