AC once was cold... but not anymore... Troubleshooting?
06-29-2011, 11:09 PM
#1
Pro
Thread Starter
Join Date: Aug 2006
Location: Schaumburg, IL.
Posts: 548
Likes: 0
Received 0 Likes
on
0 Posts
AC once was cold... but not anymore... Troubleshooting?
My AC used to blow nice and cold... not anymore. I started troubleshooting the system last weekend. My first order of business was to resolve my engine bay vacuum leaks. I found two... First was on the left side of the engine at the canister by the intake the short vacuum line was totally disconnected from the 4 way fitting that hides nearby. the second was a fun one to get to. Vacuum solenoid in front of the MAF. The vacuum hose that is on the front (firewall side) was totally off the solenoid. I had to remove the airbox and the MAF to get my arm up front and plug that one back in. My ac has been working for two years with these two vacuum leaks.
So I turn on the air to Max and the compressor clutch turns on and runs for about 5 seconds and then shuts off. It cycles with a duty cycle of 5 seconds engaged and 25 seconds disengaged. I wasn't sure why... kept digging. but 5/25 wasnt producing much cold air. I hooked up the Low/High manifold guages and noticed the pressure was way higher than all the specs I could find for the 993. It seems as if 30-40psi low side is normal for MOST cars. the 993 calls for a low side of 9-16psi from what I could find. the High side was high too over 350psi Hmm it appears as if the pressure switch is cutting the clutch on and off. I decide to evacuate down to about 5 psi. now at ~5psi I go back to max AC and now the clutch engages and stays engaged. The pressure switch appears to have been cutting it as suspected. I didnt run it long like this as 5psi is under spec. So I started to charge it back up. I put most of a can into the system to bring it back up to ~15psi @2000 RPM low side. Now my high side fluctuates from 250-300psi depending on compressor/condenser fan running. the low side connection to the compressor now feels cool again but not cold like it once was. Cool air is blowing out but by no means is it working like it was. In the process of monitoring my high side pressures I realize there is no low speed on my condenser fan, it's either High or OFF. Bad ballast resistor probably... i have not had time to troubleshoot the front of car cooling yet but it appears as if my pressure switch is functioning. Anyone know if a ballast resistor will prevent ac from blowing cold? It appears as if i dont have a leak as I was over pressure to start but things used to work fine... Anyone have any ideas. Would like to get my COLD air back. plan on troubleshooting the front of car stuff this weekend. Any pointers from anyone?
Nick
So I turn on the air to Max and the compressor clutch turns on and runs for about 5 seconds and then shuts off. It cycles with a duty cycle of 5 seconds engaged and 25 seconds disengaged. I wasn't sure why... kept digging. but 5/25 wasnt producing much cold air. I hooked up the Low/High manifold guages and noticed the pressure was way higher than all the specs I could find for the 993. It seems as if 30-40psi low side is normal for MOST cars. the 993 calls for a low side of 9-16psi from what I could find. the High side was high too over 350psi Hmm it appears as if the pressure switch is cutting the clutch on and off. I decide to evacuate down to about 5 psi. now at ~5psi I go back to max AC and now the clutch engages and stays engaged. The pressure switch appears to have been cutting it as suspected. I didnt run it long like this as 5psi is under spec. So I started to charge it back up. I put most of a can into the system to bring it back up to ~15psi @2000 RPM low side. Now my high side fluctuates from 250-300psi depending on compressor/condenser fan running. the low side connection to the compressor now feels cool again but not cold like it once was. Cool air is blowing out but by no means is it working like it was. In the process of monitoring my high side pressures I realize there is no low speed on my condenser fan, it's either High or OFF. Bad ballast resistor probably... i have not had time to troubleshoot the front of car cooling yet but it appears as if my pressure switch is functioning. Anyone know if a ballast resistor will prevent ac from blowing cold? It appears as if i dont have a leak as I was over pressure to start but things used to work fine... Anyone have any ideas. Would like to get my COLD air back. plan on troubleshooting the front of car stuff this weekend. Any pointers from anyone?
Nick
06-30-2011, 05:45 AM
#3
Rennlist Member
I am sorrry, I cannot comment on the A/C pressure issues. Your condenser fan will run on high if the low resistor is shot.
But, have you checked your two mixing flaps? If they both are stuck in the open position hot air from the engine will overshadow the cooling from the evap? Have a look here for details:
www.ccu.tore.bergvill.com
Cheers,
Tore
But, have you checked your two mixing flaps? If they both are stuck in the open position hot air from the engine will overshadow the cooling from the evap? Have a look here for details:
www.ccu.tore.bergvill.com
Cheers,
Tore
