Jump to content

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

How does the AC Expansion valve work?

Recommended Posts

Not an AC expert and for some reason since I have gotten the system charged up the low side seems perfect  but the high side

just keeps climbing?  I looked at the expansion valve and don't see anything like a normal capillary tube type where the temp is

monitored by it and opens and closes the expansion valve?  All I see is a little disk looking thing on one end of it where it attaches

to the evaporator.  So I am wondering if it may be not opening does anyone know how it should work?  This is a 1999 c2 and just

wondering what actuates it if anyone knows please.


Thanks in advance,


Link to comment
Share on other sites

Hey Ahsai  thanks, got most of those documents already on file.  I also found a great deal of info

just tooling around different forums most say its built in on these particular valves so its not visible

outside.  But thanks anyway!!



Link to comment
Share on other sites

Hi John,


Yes, there's nothing on the outside of the expansion valve. As you charge (refill) via the low pressure port, the pressure will increase on the high pressure side as well so that's normal. The valve actuation (regulation) is all done by the internal parts of the valve.


Are you experiencing problems currently with the a/c or you're just curious of how it works?


BTW, the document in the link above, pdf page 16 explains how the expansion valve works and pdf page 87 shows the normal high and low side pressure as a function of ambient temperature.

Edited by Ahsai
Link to comment
Share on other sites

Yes what I have is the low side is about in the correct range 70-ish and at first the high side seems ok but here in Alabama right now temps are in the high 90's so I have some fans blowing on the condensers to try and portray going down the road at a moderate speed but he high side is going off the chart over 400 so I cut the

air off cause I know that is way to high.  So just trying to figure out if the expansion valve is not working properly.  That what the old rule is if the low side is fine and the high side is high there is a blockage of the orifice or in the cars case maybe an issue with the expansion valve.




Link to comment
Share on other sites

You read my mind, we did the evac and weighed the refrigerant back in and then took a hose pipe and run water over the

condensors and vo'la!!! got it. The high temp and maybe it was a little overcharged,and maybe the need for the hose pipe to be run on it, so whichever it was all cleared up and we now have cool air!!!



Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.