A/C Compressor Switches On/Off Too Frequently
 

1987 560SL

My A/C cools VERY WELL and it's hot in Atlanta now!!! After about 5 minutes of operation, the compressor switches on and off rapidly. I bridged the connections for the Dryer Pressure Switch and the problem goes away! There are no bubbles in the site glass and my friend checked high/low pressure and it's correct.

Will a bad switch work erratically? I always thought they just failed or leaked...but I know anything is possible!!

Also, since I am way familiar with vintage cars that didn't have a pressure switch, I'd like to just bridge the connection for the summer months and replace in the Fall when I have the time to evacuate the system and change the switch. I am astute enough to know if the air isn't cooling and the compressor is engaged to immediately shut off the A/C system.

Thanks for your help!!

When my '87 AC had the same symptom, it turned out to be a somewhat hard to find ceramic resistor in the receiver/drier circuit. Look on the passenger side of the radiator following the wiring along the vertical frame toward the top of the frame, and you'll find it. Very inexpensive (less than $15) and simple to install.

unless I'm mistaken all systems will have either a pressure or a temperature switch to cycle the compressor. System isn't meant for the compressor to run all the time.