Heater System: Other Ford Econoline E350

Blower Switches

Control panel mounted front and rear blower switches have 4 positions: low speed, 2 intermediate speeds and high speed. Rear blower switch can be overridden by blower switch on instrument panel. Auxiliary switch also has an OFF position. When function selector switch is in OFF position, blowers will not operate.

Note. Function selector switch positions are indicated by standard function icons.

Function Selector Switch

The function selector switch can be placed in OFF, vent, floor, mix and defrost positions. The position of function selector switch determines whether function doors are open, partially open or closed. Function doors direct airflow to selected outlets. The 3 vacuum motors and doors are outside/recirculated air, defrost/panel and defrost/floor.

FUNCTION SELECTOR MODES

Note. The function selector switch does not affect the temperature blend door. Any desired temperature, from full cool to full warm, can be set regardless of which function control mode is selected.

OFF

In OFF mode, full vacuum is applied to outside/recirculated air and floor/defrost vacuum motors. Vacuum is not applied to panel/defrost vacuum motor. Blower motor is off. Temperature can be adjusted as desired. Recirculated air is directed to floor outlets.

Vent

In vent mode, outside air is allowed into system. Vacuum is not applied to outside/recirculated air vacuum motor. Full vacuum is applied to panel/defrost and floor/defrost vacuum motors. Airflow is directed to panel outlets. Blower motor speed and temperature can be adjusted to desired settings.

Floor

In floor mode, outside air is allowed through system. Vacuum is not applied to outside/recirculated air vacuum motor. Full vacuum is applied to floor/defrost vacuum motor. Vacuum is not applied to panel/defrost vacuum motor. Airflow is routed to floor outlets. Blower motor speed and temperature can be adjusted to desired settings.

Mix

In floor/defrost mode, outside air is allowed into system. Vacuum is not applied to outside/recirculated air and panel/defrost vacuum motors. The panel/defrost and floor/defrost vacuum motors receive partial vacuum, allowing equal outlet airflow. Blower motor speed and temperature can be adjusted to desired settings.

Defrost

In defrost mode, outside air is routed through system and out defroster outlets. Vacuum is not applied to outside/recirculated air, floor/defrost and panel/defrost vacuum motors. Blower motor speed and temperature can be adjusted to desired settings.

TEMPERATURE CONTROL SWITCH

Temperature control switch is part of a temperature control module, attached to control frame with 2 screws. The module contains a printed circuit board and a linear potentiometer. The potentiometer switch is mechanically coupled to potentiometer wiper.

The temperature blend door actuator contains a reversible electric motor and a potentiometer. The potentiometer wiper is connected to the actuator output shaft and moves with the output shaft to indicate position of temperature blend door.

Battery voltage is applied to ends of each potentiometer. The voltage available at each wiper indicates position of the potentiometer. The actuator wiper voltage is sent to the control module and matched with the wiper voltage of the module potentiometer. The printed circuit board then drives the actuator motor in whichever direction is necessary to make the actuator wiper voltage agree with the control wiper voltage.

BLOWER MOTOR INOPERATIVE

Turn ignition on and blower switch momentarily to each position. Check for voltage and ground at blower motor connector. If voltage and ground are present, test blower motor. If voltage is not present, check fuse No. 13 (15-amp) at instrument panel fuse panel and fuse No. 13 (50-amp) at engine compartment fuse box, replace fuse(s) as necessary. Check function selector switch and wiring. If ground is not present, check blower resistor, blower switch and wiring.

BLOWER MOTOR ONLY RUNS IN LOW

Check blower switch. Check wiring for open circuit. Check ground circuit for open circuit. Check for open blower motor resistor.

BLOWER MOTOR ONLY RUNS IN HIGH

Check for open blower motor resistor. Check for open thermal limiter. Check blower switch.

AIR FLOWS FROM WRONG OUTLETS

Test vacuum check valve. Check for vacuum leaks and inoperative vacuum motor. Check for correct vacuum hose routing. (Scheme 4)

INSUFFICIENT HEAT

Ensure cooling system is operating properly. Check heater system hoses and core for coolant flow. Test vacuum check valve. Check temperature control switch. Check wiring between temperature control switch and blend door actuator.

ERRATIC FUNCTION MODE SELECTION

1. Check for vacuum source at engine manifold and vacuum canister. Ensure check valve is installed correctly. Check for leak at vacuum controller. Ensure all vacuum hoses are correctly routed and connections are tight. (Scheme 4)
2. Check vacuum motors and vacuum hoses for leaks and kinks. Check all mode doors and blower motor for binding and foreign material.

BLOWER MOTOR

Unplug blower motor harness connector. Using a jumper wire, connect battery voltage to blower motor connector Orange/Red wire terminal. Connect a second jumper wire from ground to blower motor connector Orange/Black wire terminal. Replace motor if it does not operate at high speed.

BLOWER MOTOR RESISTOR

Note. Blower motor resistor controls medium-high, medium-low and low blower speeds. Blower motor resistor resistance test specifications are the same for both main and auxiliary systems.

Remove blower motor resistor. See BLOWER MOTOR RESISTOR R & I under REMOVAL & INSTALLATION. Measure resistance between indicated terminals. (Scheme 3) See BLOWER MOTOR RESISTOR RESISTANCE TEST table. If resistance is not as specified, replace resistor.

BLOWER MOTOR RESISTOR RESISTANCE TEST

Scheme 3

BLOWER MOTOR SWITCH

Remove control panel from dash. See CONTROL PANEL under REMOVAL & INSTALLATION. Check for continuity in all switch positions. See BLOWER MOTOR SWITCH CONTINUITY table. If continuity is not as specified, replace blower motor switch.

BLOWER MOTOR SWITCH CONTINUITY

FUNCTION SELECTOR VALVE

Place function selector switch in specified position. (Scheme 4) Using a vacuum gauge, check for presence or absence of vacuum as specified. If test results are not as specified, check for kinked or broken vacuum lines. If vacuum lines are okay, replace function selector valve.

Scheme 4