hello i have a 259b3 tring to fix the ac it has no voltage at the compressure clutch got a wire diagram checked all relays replced fan switch.On ac relay at pin 87 there is no volate i can appy 12 volts comp clutch kicks on. when i turn the switch on for ac and the blower fan the conderser fans both run on high.My qwestion is there an ac control unit that runs the condser fans and applys power to pin 87 at ac relay.Also checked ac pressure switch and bypased it still wont turn on ac relay.Any help would be apprecated.
You have an electrical schematic. Doesn't that tell you.? Can you give a machine Serial Number please. Also if your schematic has a Cat Publication reference on it please quote that as well.
Beyond the deeper electrical diag I’ll start where I usually do…is it charged? As we all know, system low enough and it won’t close the low pressure switch. Overcharged and the high is open.