Weak Compressors, or bad orifice tube?

Friendly format provided to inquire about automotive a/c systems.
Archived Forum

Moderators: bohica2xo, Tim, JohnHere, Dougflas, HECAT

99dubj
Posts: 8
Joined: Sat Aug 01, 2020 5:47 pm

Re: Weak Compressors, or bad orifice tube?

Postby 99dubj » Thu Aug 06, 2020 7:15 pm

Al9 wrote:Really weird look for an orifice tube, i swear i've never seen one like this before. The two differently sized holes on the front and the spring looking thing (rather than a single metal pipe surrounded by plastic and filtering media) lead me to believe that it's some kind of a variable flow orifice tube (look up patent US5081847A to understand how one works) but i could be wrong.


AI9, you are correct, its a VOV. I searched everywhere on the jeep forums and only found one post mention it. Made me realize that my service manual is 99-04. I bought a 99 specific service manual and sure enough that line contains a variable orifice valve. I was able purchase a factory line (which is discontinued). I will post up results once it arrives.

Thank you all for the help!
Al9
Posts: 225
Joined: Tue Mar 10, 2020 3:26 am
Location: Southern Europe

Re: Weak Compressors, or bad orifice tube?

Postby Al9 » Fri Aug 07, 2020 4:25 am

Likely not enough flow restriction in limited compressor capacity conditions (the higher than normal suction at idle).

VOVs try to mimic certain aspects of how cross-charged TXVs operate, albeit they can't finetune superheat.
Dougflas
Posts: 351
Joined: Mon Apr 18, 2016 6:10 pm

Re: Weak Compressors, or bad orifice tube?

Postby Dougflas » Fri Aug 07, 2020 5:44 am

VOV's work better for low speed as in a mail delivery vehicle. For regular operations, just use a regular orfice tube. Superheat is not used in MVAC due to the ever changing conditions.
99dubj
Posts: 8
Joined: Sat Aug 01, 2020 5:47 pm

Re: Weak Compressors, or bad orifice tube?

Postby 99dubj » Sat Aug 22, 2020 8:31 pm

Just wanted to update. I received my factory hard line with the variable orifice valve and I installed it last night. Charged up my system and pressures and temps we perfect. As Dougflas stated the VOV definitely works better at idle and low speed. This is an advantage for me as this vehicle is for offroad and trails and driving slow most of the time anyways. On highway today I was seeing temps in the 46-48 range 88 outside and 90% humidity. At idle it was 42-44.

Out of curiosity, in the future if I ever need to do this again and went with a regular orifice tube, I would have to buy an orifice tube repair kit. If the OT I tried was .052, I would size down and experiment with sizes?

Greatly appreciate the help guys. It was a pain, but a great learning experience.
Al9
Posts: 225
Joined: Tue Mar 10, 2020 3:26 am
Location: Southern Europe

Re: Weak Compressors, or bad orifice tube?

Postby Al9 » Sun Aug 23, 2020 1:43 am

Excellent, so now you can see how an oversized expansion device (whether TXV, OT or VOV) can mess cooling up really bad.

Now some complaint to whoever marketed the replacement liquid line equipped with the green o-tube is in order. I'd ask them about the correct fixed orifice tube size or VOV part number.

Return to “Automotive Air Conditioning Forum”