International Lancia Forums

Last autumn, I have refilled the aircondition of my Thema V6 '92 (S2) with R413a because the power of a/c was very low. After that, I had the impression that everything would be o.k.

Meanwhile, it is warm outside and the power of the a/c is not enough to cool the car down. After starting the car, the compressor works for one minute, then stops for 15-20 seconds and works again for 15-20 seconds, stops for 15-20 seconds, works for 15-20 seconds etc.

The return line from the evaporator to the compressor ist cold (water condenses on it), so it seems that it is enough refrigerant inside. But why stops the compresser even the air is still to warm? Blocked evaporator vent? Malfunctioning pressure or temperature sensors?

Another problem: The air is blown always in "VENT"-position, even if I press any other button (the LED changes, but not the air). In "AUTO"-mode the LED shows the windshield-position, but blows the air also in "VENT"-position. If it is colder outside, everything works fine again.

I have already tried to use the diagnostics of the a/c unit by pressing "AUTO" and "VENT" at the same time (and relasing the "AUTO" button first), but no effect.

Any ideas?

The problem of the air always coming out the Vent and nowhere else is most likely caused by the servo motor that moves the vent not working. There are three servo motors in the system and I have had 2 stop working (in 2 cars). They can be fixed though as the problems is either due to the small variable resistor being dirty, or the contacts between the gearbox/electronics section of the motor and the actual motor. With a bit of careful cleaning and/or soldering I got both motors working again - much cheaper than replacing the motors. If you do pull them apart take care to mark the positions of all the gears and the variable resistor shaft - otherwise things wont quite work as expected when you put it all together again.
There is also a small motor which drives a small fan to blow air over the temperature sensor - this tends to get clogged with dust and can slow or stop the fan which could also affect the output of the a/c.
hope this helps

Where can I find the fan that blows air over the termo sensor?

Christian

If you remove the a/c control unit, radio housing and the instrument binnacle you can get a good view of the motors that control the heater and vents. They are mounted on a bracket, which is fastened by 2 (3?) screws, in the centre of the dash. The fan that blows air over the temp sensor is mounted on this bracket and has a tube running from it to the sensor for air to travel through. It is easiest to remove the bracket as one piece (with all three motors attached).
Bear in mind that my car is right hand drive - not sure how easy it is to get at on a LHD car.

The low power problem of the a/c was caused by three points:
1. The poll filter was totally blocked by dust and dirt.
2. Because the poll filter was blocked, the ventilation fan caused a negative pressure and sucked the rotten seal of the ventilation fan case into the fan. The seal has been spread in small black particles into the passengers room. Because of this, there was no seal at the ventilation fan case anymore and the fan drawed a second stream of air from the engine room.
3. The pre-sieve of the drier was partly closed by dirt. So, not enough refrigerant could pass the drier and the evaporator (i.e. the pressure before the drier was much higher than behind the evaporator). The a/c specialist simply removed the pre-sieve of the drier.

First, I have replaced the poll filter (30 Euro). Then, I closed the ventilation fan case with a 15mmx20mm rubber string bought at an industrial store (3 Euro) and fixed it with sticking tape. Finally, the pre-sieve of the drier has been removed and the a/c system has been filled with 1,06 kg R413a again.

Now, the a/c is working really fine! (But I still have the air distribution problem: always blowing all the air in "VENT" position - mightbe the allknown stepper problem).

Best regards,

Daniel