Evaporator and Expansion Valve Service

Evaporator service:
- Check water drains.
- straighten bent fins (a tool is available locally).
- A frost ring on a tube indicates a restriction. (On some vehicles, the evaporator and expansion valve can be accessed by removing the glove box.)
- The evaporator is unit replaceable.

On some E36 vehicles, condensation may cause oxidation on the evaporator tubes and fins; small, white flakes of aluminum oxide may be blown out of the vents under certain conditions. Replacement evaporators coated with polyurethane are available. See TSB 64 06 93 (3791) for details.

if moisture gets into this system, it may freeze and clog the expansion valve. The A/C system may operate normally for a while, but then stop cooling. Then, as system temperature increases, the ice melts. The system works again for a while, until moisture freeze-up causes it to stop again.

The expansion valve is unit replaceable; there are no adjustments or repairs.

The evaporator temperature sensor can be checked using the DIS, on IHKR and IHKA systems.

With the IHKS system, to check the evaporator temperature sensor, access the sensor by removing the lower trim panel and the instrument panel lower cover on the driver's side. Pull out the sensor and measure its resistance with a DVOM, or disconnect the evaporator sensor and measure its resistance, in place.

Evaporator Temperature Sensor Specifications: