A/C Help. Expansion Valve blocked? Drier Clogged?

[Syncade]

My air conditioning is confusing me. I have searched all morning for answers.

CAR: 1997 240sx SE. All OEM. 198,000 miles.


Basically I took my car to get a recharge this morning (AC only gets cold at highway speeds). The mechanic showed me:

LOW PRESSURE SIDE is way too high (70ish)

HIGH PRESSURE SIDE was basically normal


Now, we both knew there was a clog in the system, but I old him to go ahead and purge/recharge to see if it would clear up the problem. After the vacuum/recharge, we saw:

LOW PRESSURE SIDE is wayyyy too high (75 after just 1 can of R134a)

HIGH PRESSURE SIDE was basically normal


And now after this, I have no cool air, and my expansion valve is "hissing" when I turn the AC on. I know that sometimes they hiss when there is low refridgerant, which would make sense in this case, as we only added 1 can.

My compressor is fine. All electronics/sensors SEEM to be working fine.


My questions:

1. Do 240sx's clog Expansion Valves frequently? I plan to replace this.

2. Should I replace my Drier/Liquid tank with an OEM unit, or generic (Advance auto) unit? Is this necessary?

3. Is blowing compressed air through the system a bad idea? (due to moisture contamination). I would assume so, and I don't plan to, but I am just curious.

4. Has anyone encountered a similar problem.




Anyone with experience please chime in. Thanks.

[mendozasport]

first off , if there was a clog your low side will drop into a vacum and the hi side would be excesively high, the expancion valve could be your problem its not modulating correctly, so i would start there , no contaminents should be in the system period so an expancion valve should last the life of the car , but unfortunatly refrigerant leaks cause the compresor to pump more oil into the lines causing issues and it also seams that more and more i see refrigerant cans with oil in them

[Syncade]

Yes the more I read online, the more I agree with you.


I am sort of confused as to if 240sx's have an oriface in the line off of the compressor (or is the condensor?). There isn't one, correct?

[inopsey]

do you have air flowing across the condenser? you should be able to feel the air being sucked across when you place your hand on the condenser.

any moisture introduced into the system is removed by vacuum before the refrigerant charge is done. if you properly test for leaks before recharging all moisture is removed.

its a good idea to change your dryer whenever your ac is opened up as moisture and air will cause the system to run inefficient.

[ka4life87]

Try replacing expansion valve and do complete system flush, if not the compressor is probably bad, high side pressure bleeding to low side

[godsmack]

^ I agree. expansion valve is probably stuck open. that is what would have an oriface in it. pretty much the compressor feeds into the high side and if that's normal and the low side is high then the expansion valve is shot. replace that and i always replace the drier when opening up the system.

[Syncade]

I'll be replacing both this weekend. Thanks for the help guys.

[inopsey]

I'll be replacing both this weekend. Thanks for the help guys.

even if you have a water logged dryer and a sticky expansion valve, if you have no air flow across the condenser it will do you nothing for in city driving. (you mention it only blows cold on highway)

[OldSchool240sx]

Having the exact same problem in my 89. Had cold air only at highway speeds, had the r12 evacuated, refilled with 134a (took less than half a can to fill it), replaced the reciever/dryer, now it wont blow cold at all. my next step will be the expansion valve as well. let me know if that works for you!