Air Conditioning (Alfa 33 907 Series)

April 20, 2020 14

Another obstacle was the hiring harness. Since the car had a front end accident the part of the wiring harness that drives the condenser fans was missing. Moreover I found out to my surprise that the harness had been unprofessionally "repaired" during in the past; many of the cables were cut out, some replaced with completely unsuitable cables, no color coded cables used and many rolls of stickly vinyl tape used.

Since this is a high standards restoration, the harness was recreated using new cables and connectors. These are really affordable items which can be easily found at a local automotive electric shops.

Alfa 33 907 Series Air Conditioning > AC Wiring Harness Repair

This is the connector which acts as a bridge between the evaporator and main harness. Notice the amount of vinyl tape wrapped around the harness; as soon as the PVC tape was unwrapped, a real mess was hidding. Cables were cut and twisted together (not even soldered!), unportected by PVC tape and on top of that some of these cables had melted insulation. This means that during the past a serious electrical fault occurred in the donor car.

Relay and fuse holders.

Wiring in the relay holder is in good condition.

These connectors and wires will need some attention.

The best approach will be replacing the cables or the spade connectors with new ones.

Traces of current overloading. This has to be rectified.

This is the heater fan switch connector. Luckily no fault here.

New cables will replace the old and melted ones.

Cloth tape along with new spade connectors and relays. The harness from the donor car did not have any relays, so new ones were bought from the Alfa dealership.
Notice the nuts on the left; these are special nuts from Alfa which are fitted on the square holes on the chassis used to attach various components.

This is the electronic thermostat which has the primary role of regulating AC operation based on the temperature setting on the control panel and the temperature reading from the frost sensor (clamped on the evaporator tubing).
When the values from the two sources are equal then this device stops operation of the compressor and condenser fans; as temperature on the evaporator pipe increases then the thermostat triggers compressor and condenser fans and the system cycles again. This process of A/C operation is called cycle on/cycle off.

Trinary Valve. This is actually a triple-switch based on the refrigerant pressure.
If the pressure on the system is normal then it allows operation of the AC compressor and left side fan. When the pressure on the system rises (due to high ambient temperature or when there is no proper air flow on the condensers eg. during traffic) it triggers the right side fan to help the system lower its pressure and increase the cooling effect.
In addition, it serves as a minimum/maximum pressure switch in the case of a malfunctioning subsystem of the A/C unit (compressor or condenser fan) and it is installed on the filter/dryer.

This is the evaporator harness after the restoration with every connector explained.

This is the main harness after the restoration with every connector explained.
The condenser fans wiring will be created when the main wiring is installed on the vehicle.