in my p38 when you press the all program button on hevac unit the fans should go up to high speed but there not any ideas what it could be the fans are workign but not clicking onto high speed and also no book with question mark on front of unit

thanks

Are you sure the system does not wait until the engine has warmed up slightly before going into defcon 5?

it does take a bit to get going!

Do the heated seat buttons work? There is a specific live that if it fails you get no program button no high speed fan and no heated seats.

the lights work on heated seats or do they physically need to be getting warm not tried will try

even with wngine warm the fans dont kcik into high speed when pushing all program button can only do it manually

anyone?

Sorry bit delayed getting back to you. If the buttons are lighting up then the ignition position 1 and 2 lives are ok.
The system as garioch43 mentioned, does wait until it reaches a safe operating temperature. This prevents the evaporator from freezing.

You really need to connect up some kit to it and look at the inputs to the hevac unit. Unfortunately even though the book symbol isn’t on doesn’t mean we don’t have any faults.

For instance if either the engine coolant temp or the Evaporator temp sender is showing -40, to the Hevac unit this isn’t a fault. To us it is because it is preventing the unit from working correctly. The Hevac unit would sit there all day long waiting for the temperature to warm up and it never will.
The serial data on the diagnostic kit can paint a very clear picture on how the system is operating.
It is frustrating because this info doesn’t fix your fault but it would be a case of peeing in the wind without knowing what Values the Hevac unit is seeing.

thanks mate