Page 1 of 2

High Pressure Mystery

Posted: Tue Sep 12, 2017 4:54 am
by chuckwp
Trying to help out a fellow tech. in the shop. !996 VW Eurovan came into the shop with no cooling. Single A/C - front only. Technician replaced compressor, drier and espansion valve, flushed out condenser and evaporator, evacuated system and charged with correct amount of correct refrigerant. When first starting vehicle A/C works normally. However, after running a short while the high side jumps way up to 400 PSI!! Cooling fans working properly. Tried a know good pressure switch with no change. It seems like a restricted/clogged condenser but, the technician said the condenser flushed out well. Again: new compressor,drier, new expansion valve, proper charge amount, condenser fan working. Out of ideas. Input?

Re: High Pressure Mystery

Posted: Tue Sep 12, 2017 6:10 am
by Cusser
Is that a serpentine type of condenser? Those are more likely amenable to reverse flushing than the parallel flow condensers, where solvent can bypass many passages. That's why parallel condensers are most often just replaced with new.

Re: High Pressure Mystery

Posted: Tue Sep 12, 2017 5:38 pm
by chuckwp
[quote="Cusser"]Is that a serpentine type of condenser? Those are more likely amenable to reverse flushing than the parallel flow condensers, where solvent can bypass many passages. That's why parallel condensers are most often just replaced with new.[/quote
I am not sure what type of condenser it is but, that could definitely be the problem! I will tell the tech. to check into it before he tears all his hair out! Thanks for the tip.

Re: High Pressure Mystery

Posted: Wed Sep 27, 2017 4:09 am
by chuckwp
Update. Condenser has been replaced. Still excessive high pressure. (450 PSI) So, all major components have been replaced except evaporator. New compressor, condenser, drier,and expansion valve. Refrigerant charge level is correct and oil amount verified. It acts like a restriction in the high side or, an over charge but, that is not the case. At a loss. What are we missing?

Re: High Pressure Mystery

Posted: Wed Sep 27, 2017 8:38 am
by bohica2xo
Condenser airflow issue.

Spray the condenser with water & watch the pressure drop like a rock.

Fan(s) not working / worn out & not reaching full speed etc.

Re: High Pressure Mystery

Posted: Wed Sep 27, 2017 4:58 pm
by chuckwp
bohica2xo wrote:Condenser airflow issue.

Spray the condenser with water & watch the pressure drop like a rock.

Fan(s) not working / worn out & not reaching full speed etc.

Fans working correctly. Does not make sense. Cannot find a restriction in the high side. No cold spots on the condenser. When/if we figure it out I will post the fix.

Re: High Pressure Mystery

Posted: Thu Sep 28, 2017 6:59 am
by bohica2xo
400 psi is a condenser issue. HEAT is not being removed.

Spray the condenser with water & watch the high side pressure.

Re: High Pressure Mystery

Posted: Thu Sep 28, 2017 9:04 am
by Cusser
bohica2xo wrote:400 psi is a condenser issue. HEAT is not being removed.

Spray the condenser with water & watch the high side pressure.


Have you tried this? bohica2xo knows his stuff, but cannot be there hands-on, so at least try this and report back to him.

Re: High Pressure Mystery

Posted: Thu Sep 28, 2017 12:07 pm
by Dougflas
After you spray the condenser with a hose and find that the high side drops like a rock, check to see if the fans are turning in the proper rotation. Also see if there is air flow going thru the condenser and radiator. Definitely appears to be a condenser air flow problem. This would not be the first time air went through the fans and bounced off the condenser instead of going thru it.

Re: High Pressure Mystery

Posted: Thu Sep 28, 2017 1:50 pm
by Cusser
Dougflas wrote:After you spray the condenser with a hose and find that the high side drops like a rock, check to see if the fans are turning in the proper rotation. Also see if there is air flow going thru the condenser and radiator. Definitely appears to be a condenser air flow problem. This would not be the first time air went through the fans and bounced off the condenser instead of going thru it.


"You know what, Skipper? You're right too !!!" - Gilligan from Gilligan's Island