VW Passat 1998 A/C heating won't start. Please help!!!

[nacid]

Hi,

I have a VW passat 1998 reg. the a/c compressor's gone and it doesn't cool. That does not bother me and probably I will change the compressor in the summer. The problem is that the heating was fine till few weeks ago. Now when you start the car, the climate control module flashes for 15s and the fans do not work at all. Sometimes if I have not used the car for a few days the fans start, and the heating is fine. When I switch the engine off and start it again no more heating :).

Vag-com says f129 pressure switch problem but how come sometimes the heating works, sometimes not?

Could it be a sensor somewhere or the climate control module itself?

Please help as I’m gonna freeze in the car soon :))))

Nick

[adamss24]

CHECK THE COOLANT PRESSURE SENSOR AND THE HIGH PRESSURE SWITCH FOR CORODED DAMAGED CONECTORS/WIRES. THE COOLANT TEMP SENSOR MAKES THE ECU THINK IS COLD OUTSIDE AND SHUTS THE AC COMPRESSOR OFF. HEATING IS A DIFFERENT THING FROM AC SYSTEM, THEY COME TROUGH THE SAME VENTS BUT THEY ARE DIFFERENT SYSTEMS. THE MODULE FLASHES AT START UP BECAUSE THERE ARE FAULT CODES IN THE MEMORY.

[nacid]

CHECK THE COOLANT PRESSURE SENSOR AND THE HIGH PRESSURE SWITCH FOR CORODED DAMAGED CONECTORS/WIRES. THE COOLANT TEMP SENSOR MAKES THE ECU THINK IS COLD OUTSIDE AND SHUTS THE AC COMPRESSOR OFF. HEATING IS A DIFFERENT THING FROM AC SYSTEM, THEY COME TROUGH THE SAME VENTS BUT THEY ARE DIFFERENT SYSTEMS. THE MODULE FLASHES AT START UP BECAUSE THERE ARE FAULT CODES IN THE MEMORY.

My ac compressor does not work. I am not worried that it does not blow cold air. the problem is the heating starts just from time to time. any idea what could it be?

[adamss24]

Cold/hot temp motor flap. If you have a Vag com you could cycle on and off all the AC/heating components. I asume that the blower works ! Read what i said in my post and it may fix your AC or go to dealer and pay hundreds of quid to fix. Also with vag com you could see if the temp sensors, high/low pressure switches, and temp sensors(they are about 3 of them !) all are within spec ! Also remember that AC system should be turned on at least once a week in the winter to prevent damage to the compresser.