AC cool, not COLD
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Joined: Jul 2009
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1985 500SEL, 1984 380SL, 2004 CLK320, 1998 SLK230
AC cool, not COLD
OK... Here's my problem: I have a 1985 Mercedes 500SEL that I bought last year. The AC was blowing hot. The low pressure switch was activated. Since it is a R12 system, I bought some Freeze 12 to top it off. I pulled a vacuum overnight, and then put in Freeze 12 (a R12 substitute). The compressor then kicked in, after the low pressure switch closed. The outside temperature was 83 degrees Fahrenheit. The low side gauge read 50, the high side read 250. The air was cool, not cold. I drove the car a few days. This morning, I decided to add a little more Freeze 12. As I was adding the Freeze 12, it seemed like a safety valve on the AC compressor started releasing (a popping noise). The low side pressure never exceeded 65 pounds. I stopped adding Freeze 12, the popping noise stopped (maybe the pressure equalized inside the system). It cools a little better, but not like it should. Any suggestions on what I should do next?
I also should say, my 1985 380SL was also blowing cool air. I added some Freeze 12 to that system. It now blows cold, like it should. (low side – 40 lbs, high side 250 lbs, outside temperature was 95 degrees Fahrenheit).
David Kelley
I also should say, my 1985 380SL was also blowing cool air. I added some Freeze 12 to that system. It now blows cold, like it should. (low side – 40 lbs, high side 250 lbs, outside temperature was 95 degrees Fahrenheit).
David Kelley
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Joined: Mar 2006
Posts: 3,254
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From: Louisiana
03 E500 and Corvette
Stop don't put any more freon in
. 50 # is too high on the suction side for the 250 on the discharge for 80 degree day. It will be higher with higher daily temperatures. I suspect you have a expansion valve not fully opening or weak compressor. If the compressor is putting out 250# on the discharge at 80 F this is within range for the system so the compressor is a low probability of being the issue. I would look at the expansion valve and or evap coil is clean with working dampers. This means you should have good strong air flow. Also don't forget dampers will prevent air flow. If you have a hot air damper open it will not allow the system to cool further.
The pressures were ok before you added the freon. The popoff you heard many have been a relief valve as your head pressures are getting high. What concerns me is the low pressure is high. I normally don't go over 34# on the suction side and your 50+ is way over what I would normally use. This comes from too much freon in the system. If you continue to put more freon in the system on a hot day you might blow the high pressure hose.
. 50 # is too high on the suction side for the 250 on the discharge for 80 degree day. It will be higher with higher daily temperatures. I suspect you have a expansion valve not fully opening or weak compressor. If the compressor is putting out 250# on the discharge at 80 F this is within range for the system so the compressor is a low probability of being the issue. I would look at the expansion valve and or evap coil is clean with working dampers. This means you should have good strong air flow. Also don't forget dampers will prevent air flow. If you have a hot air damper open it will not allow the system to cool further.The pressures were ok before you added the freon. The popoff you heard many have been a relief valve as your head pressures are getting high. What concerns me is the low pressure is high. I normally don't go over 34# on the suction side and your 50+ is way over what I would normally use. This comes from too much freon in the system. If you continue to put more freon in the system on a hot day you might blow the high pressure hose.
