E 350 Van L6-300 4.9L VIN E 1-bbl (1982)
Evaporator Drain Tube: All Technical Service Bulletins
A/C Evaporator Housing - Water Leaks to Interior
Article No. 85-11-16
AIR CONDITIONING - INADEQUATE DRAINAGE FROM EVAPORATOR HOUSING
LIGHT TRUCK 1975-85 ECONOLINE
During conditions of high humidity and high blower operation, evaporator condensate leaks into the passenger compartment from the A/C blower
housing, blower housing to evaporator housing flange and/or the A/C register outlets.
The fundamental cause of this leakage is that the blower is located downstream of the evaporator core (draw through system), resulting in a negative
housing pressure with respect to ambient. During this condition of negative pressure, air flow can be drawn through the drain tube into the housing
opposing the flow of condensate drainage out of the drain tube. Also, air leakage into the housing because of insufficient drain tube sealing can cause this
concern.
Due to improper condensate drainage, water can accumulate in the bottom of the temperature blend door frame assembly and spill into the blower
housing. If this condition occurs, insufficient sealing at the blower housing to evaporator housing flange and at the blower scroll cover to blower housing
may allow leakage into the passenger compartment from these areas.
An accumulation of water in the blower housing may result in water being blown through the register ducts and register outlets.
PROCEDURE:
Install the new check valve drain tube assembly which completely shuts off air flow through the drain tube, due to the negative pressure, yet allows water
to drain freely under all housing negative pressures encountered in service.
Due to manufacturing variations of evaporator assemblies, some units are more susceptible to condensate accumulation and will require rework of the
blend door frame and may necessitate resealing the lower housing flange.
The following three drain tube systems may be reworked as outlined in the following paragraphs.
Figure 18
Econoline Vehicles with (Production) Aspirator Drain Tube Built March 1984 through September 1984
Drain Tube Replacement (Refer to Figure 18)
