Heater just blows hot air will not give lower temp with air con switched on . air con pump is working

This is probably caused by a power failure to the DDCV ( dual climate control valve) or the valve its self has failed. Another common issue is a broken / corroded cable leading to the DCCV. You need to check power to the valve as the first step. A good auto elec will be able to check it out easily for you. If the valve has failed and when replaced it will still not work correctly due to lost power signal - this will be caused by control module, this unit can sometimes be repaired as the valve when it fails burns out the printed circuit tracks in the unit Hope this helps - good luck.