ac clutch cycling
 

86 300 e
in order to activate compressor clutch I have hot wired it to the fuse box (always on)
I have the correct charge in the system
I have continuity through the preasure switch
The normal system is sending 6 volts to the preasure switch (not enough to opperate the clutch)
the system of course does not cycle with this set up
with the hot wire disconected the system will work sporadically.
any help would be greatly appreciated
thanks
bill

If it is short cycling with the jumper removed it sounds like it's under charged.

I would not recommend jumpering this system. The pressure switches serve to protect the system from under or over charge damage.

Good luck,

You need to have the pressures checked. This will tell you where to start looking next. If pressures and charge are OK, I would bet on the binary cutout switch on the receiver/dryer.

Low Pressure Switch
 

I'm having trouble with my compressor not coming on too ('88 260E). There are two pressure switches on the receiver/drier one has 4" leads with a green plastic body and the other is larger with spade lugs on it. I assume one is the high/low cutout and the other is for the aux fan. Which is which?

Thanks!

The switch with the leads is for the fan. The other is for pressures.

Here is a schematic of your system. The compressor clutch is controlled by a smart relay. One of the inputs to the relay is probably has a problem or the relay itself is bad. Check the imputs - things like engine speed input, overheat input etc.




http://www.acc-controls.com/photos/Misc/300eACC.jpg

Schematic
 

Thanks Dave,

The schematic is really what I needed. My repair manual does not have one.

I keep bidding on repair CD on ebay and always get outbid. It's very frustrating sometimes.

- John