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Old 08-26-2007, 08:53 PM
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Join Date: Aug 2007
Posts: 14
88 560SL ACC problem

The Acc on our 560 "kinda" works. The outlets give off COOL air but not "COLD" air. A friend has a 560 and his ACC "WORKS". We live in central Fla. and need the Acc to be able to drive to the store and back without requiring a shower when we get home!!!
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Old 08-26-2007, 10:18 PM
Join Date: Oct 2004
Location: NC
Posts: 2,988
Three things to check.

1) Monovalve. You should be able to feal this click when you go from heat to AC. But just because it clicks it doesnt mean its OK. You may also have a bad diaphram. The only way I know to tell is to pull the 4 screws and look. This is a 20 min job and about $30.00 worth of parts for a diaphram replacement.

2) AC Charge. Are you running R12 or R134. R12 will be colder than R134. Nothing you can do except go back to R12, which will mean flush and new oil unless you know Ester oil was used.

3) AC undercharge. This is most likely your problem. Have an assistent that you trust put the car in park and hold 2000 RPM with doors and windows open and AC on. You should see no bubles or very few bubbles in the sight glass. Make sure the glass is clean and the compressor is running. The sight glass can be cleaned with a pencile eraser.

John Roncallo
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Old 08-27-2007, 10:43 AM
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Join Date: Mar 2006
Location: Upstate NY
Posts: 212
John is on target.
Try this: With the A/C on and engine warm, lift the hood and check to see if the AC compressor is "engaged". If so, check the large AC line on the driver side parallel to fender. Touch a metal area to see if it is ice cold. If so check the rubber hose on the firewall on the passenger side that comes from the monovalve and goes into the firewall. If that is hot your monovalve is open and may be bad. This will cause heat and AC in the interior exchangers giving you mmedium warm air.
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