Freightliner HVAC unit discharge Temperature sensor voltage > normal

Did you change the gray or the black sensor?

 

You were right with the gray sensor! Check voltage at the sensor at pins 1 and 2, should get 5v. If you dont, pull back the front a/c controller and check your pins at connector A8 and B6. You can also ohm those wires from the controller to the sensor. they shouldnt be more than .8 ohms tops

 

Have you physically checked voltage at the sensor? Fault codes can be weird.. Things like an open in the harness can cause a high voltage code. The only thing it can be is an open in the harness, or the front control unit can be bad. The only things that can cause a voltage high code is either an open, or a wire shorted to a power source. Here is what I would do
1. check voltage at the sensor between pins 1 and 2, should be 5v
2. disonnect and remove the CDTC sensor and ohm the sensor between pins 1 and 2- it has a very high resistance accross the sensor
3. plug the connector back in the sensor, remove the front controller and disconnect the connector on the back of the controller. measure resistance between pins B6 and A8 and it should match the reading on the sensor. If the reading matches the sensor, the front controller is bad. If the reading doesnt match, there is a short in the a/c harness between the front controller and the cdtc sensor

 

my 07 Freightliner century gave a code SID -14 4 Relay Diagonal 1 it is intermittent. Does anyone know what this means?

 

My Freightliner is showing a diagnostic code for HVAC
SPN 52331 8
FMI 7
The heater in the bunk works just fine the heater in the cab does not work

 

This is very old post BUT shot in the dark where are these 2 sensors located Gray and Black Ones ?