I'm currently contemplating replacing the leaking evaporator in my '94, and am building my parts list. FCP Groton lists two types of orifice tubes, a fixed one and an auto-adjusting one, but nothing to indicate which is meant for which car, and their write up almost suggests that the interchange, but one is a cheap, functional one, but the other is better...but I am not certain. I have the manual A/C.
Which orifice tube do I need?

Champ 6,

Can you share your parts list with us?

I am about to embark on the same project and would appreciate the opportunity to see your parts list to make sure I haven't overlooked anything.

Thanks.

I ordered the evaporator, receiver drier, and orifice tube...the fixed one. I have a vacuum pump (actually one of those cheap venturi evacuators that uses lots of compressed air, but still draws mid 20" vacuum) and a set of 134 guages. My compressor is OK, although it has the bread clip fix, and AFAIK, the condensor is OK.

While I'm at it, I'll probably pull the driver's door off and weld teh crack that makes that awful popping. It sure seems like I'm doing a lot of work on a car I just want to get through the summer with, but then again I've said that for 2 years.

Hi, I actually came across your post on google, as I'm a member here but looking for similar info for my 940.
The original orifice valve is fixed. There is a variable one that some have been promoting as more efficient, not only for cooling but for longer life of compressor and other components, as well as better mpg. It further appears that vov's may all be made by Nartron Corp in MI. I am going to contact them for more info.
It appears that the VOV, Variable Orifice Valve also known as an AAOT, Auto Adjusting Orifice Tube, is made in two versions, one for 'normal' temps of under 105, and one for severe temps of over 105 degrees. I'm near SF so the 'normal' is the way I'm going.
Many have never heard of a VOV. The AAOT term seems more widely used.
I have found that prices vary, and one place,
http://www.acsource.com/smartvov-highperformanceorificetubes.aspx
seems to have it 'on sale' for $10 for the 'normal' application. Other places list in the $20-$27 range, and a few are as high as $45. If there is only one maker as I am thinking, well draw your own conclusions.

All the above as I've said, is 'appears'. I don't say that all of it is gospel yet, but it does seem this way so far.

Thanks. I already ordered the "regular" (cheap) tube, since I don't think the car will last that much longer (long story) but I decided I would invest enough money and labor to fix the A/C for this summer. This winter, once I get a new car, I'll have a project 850 with good A/C for someone.

The fixed orifice tube should be OK for a factory R134a system in decent working condition.

In my experience, the variable orifice tube (VOV or AAOT) does what it is supposed to do. Its best results will be seen in R12 to 134 conversions (again, in my experience).


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Chris Herbst
Phoenix, AZ

1992 940 2.3 160-something-k
2005 S80 2.5T 39k

Too bad mine3 isn't decent and working ;-) but I hope it will be when I'm done.