H: Compressor Thermal Limit Switch - freightliner Park Smart Technical Information

H. Compressor Thermal Limit Switch: You must remove the top section of the
ParkSmart unit to access the switch.
This device is a normally closed switch. If the compressor gets too hot, the
thermal limit switch will open and the compressor will stop. Checking with a
meter you should always have continuity between the two terminals when it is
cool.
I. Control PCB Assembly:
Do not attempt to test the controller or compressor until you have
completely eliminated all other possibilities.
In parked mode, when you turn the Park Smart unit on, the compressor relay
LS 3 and blower/fan relay LS 4 will close. LS 3 will send 12 VOLT main
power from terminal 87, through the F 1 fuse, to the compressor controller
section of the control PCB assembly. LS 4 will send main power through it's
terminal 87, through F 4 and F 5 fuses to the blower and fan. If all other
conditions are ok, such as the high pressure switch, freeze switch and the
compressor thermal limit switch, the compressor controller will then send
voltage out to the compressor.
Check for 12 VOLT from the F 1 fuse going to the PCB controller pin C 1.
Also check for unfused 12 volts at pin C3 (Aux Battery Sense). If Aux battery
voltage is below 11.3 the ParkSmart unit will not operate in parked mode.
Before condemning an internal component or unit, try operating the unit with
engine running.
!!! Cluster Block units – see instructions page 34-37!!!
Ring Terminal Units – Follow steps below also see pages 38 - 41
If you have the correct voltage in you should have voltage out on the three
wires connected to the compressor. Disconnect the three wires , RING
TERMINAL UNITS ONLY! from the compressor. You will have to remove
plastic cap from the top of compressor.
Using a volt meter check each wire, positive on (blue, orange or yellow)
negative to battery ground. If you do not have a 6 volt pulse voltage out on each
wire, replace the controller. Pulse voltage means the controller will cycle to
each colored wire. You should see the voltage appear and disappear
continuously.
15