How do i turn my ach25 heater/ cool on with no control

check for faulty heater control module or vacuum controlled heater tap.

check the control module that controls the coolant flow through the heater core.

Heater core is partially plugged or the control valve for the heater is not working.

Hello! There is a Technical Service Bulletin TSB # NTB07-017 which calls for the replacement of the Heating and Cooling unit...I would suggest having the dealer inspect the unit when you bring their attention to this Bulletin #...There are several reasons that you do not have heat...Blocked heater core...Defective door controls...Or simply a bad thermostat...When the engine reaches operating temperature is the upper radiator hose hot an hard?...With the heat control turned to high are both heater hoses hot?...This would eliminate the thermostat and a blocked core if the answer to both questions is yes...That leaves the heat/cooling control unit and a trip to the dealer with the TSB # is in order...Guru...saailer

I’m happy to help further over the phone at https://www.6ya.com/expert/david_6df67de3b14de867

automatically. even if the motor is off.

I have the same problem, I think the door inside the heater box gets stuck when you turn it to hottest setting. Try going 1/2 or 3/4 to hot and see if it recovers without turning off the truck.

You likely have a restriction in the heater coolant hose circuit - perhaps a coolant control valve not fully opening, or a kinked hose.
Insufficient coolant volume is flowing to keep the heater core hot.
Try back flushing the heater core system with a garden hose to check flow.

CHANGE THE THEMOSTAT AND CHECK THE ANIFREEZE,WHEN THE JOB IS DONE

It could be the heater core inlet hose or connection. Since you normally have coolant flowing thru the core, when you set the system to cool, the valve closed and increased the pressure on the inlet hose for the heater core. It's less llikely that the valve itself is leaking.

left to right...
1. empty
2. e flashers
3.horn, brake lights
4.clock, trunk light, inside light, radio
5. rad. cooling fan relay (AC only)
6. right side running lights
7. left side running lights
8. right high beam and indicator
9. left high beam and indicator
10. right low beam
11. left low beam
12. reverse,turn signal and inst panel
13. main and transfer fuel pumps, auxiliary air reg., ox sensor heater
14. license plate and glove box light
15. wipers
16. rear defogger
17. heater blower (no AC)
18. cig lighter
19. rad cooling fan (no AC)
20. Heater blower (AC)
21. rad cooling fan (AC only)
22. empty
23. Ox sensor, idle stabilizer,seat belt warning relay, (Digifant only, control unit, idle boost control, idle boost valve)
24. inst panel lights, heater control lights
25. reading lamps
26. empty
27. empty
28. empty

Hope this helps...;-)