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FORD BRONCO -> CLIMATE CONTROL; heater, AC, blower motor/resistor -> Defroster
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Although we initially developed this site for 78-96 Big Broncos, information in many Links also applies to F, E Series & Cars. UPDATE; all Links via web.archive may be down; Copy orig. URL & go to http://replay.waybackmachine.org/ to search for the new archived copy
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Defroster Poor Performance TSB 98-3-18 for 92-96
Revised Defrost Nozzle TSB 88-05-16 for 87-88 Bronco & F Series
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"...The air handling system is designed to provide defrost when no vacuum is applied to any of the three air door vacuum motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak. Instead, a leak in the vacuum control circuit will send all airflow to the defroster outlets. This condition may occur during acceleration (slow leak), may exist at all times (large leak) and may happen only when certain specific functions are selected, indicating a leak in that portion of the circuit. ..." from F-150, F-250, F-350, F-Super Duty and Bronco, F-Super Duty Motorhome Chassis Workshop Manual
Source: by Ford via thedieselstop.com
A/C Switches to Defrost in MAX Mode in 92-96; "...On the newer broncos, there are colored plastic lines that go to that vacumn actuator (Miesk5 Note, it is the Vacuum Control Valve). They could be white also. they get very brittle when they get old. they will be hard plastic lines that go to the vacuum canister and possibly away from it. I had to replace those lines with rubber hose when it did the same thing. Just look for some exposed white or colored plastic looking tubes. If you fiddle with them, they will most likely break apart, then you can follow the line and replace it with rubber. You can't get those lines replaced with original, for obvious reasons..."
Source: by petlover07 at FSB
A/C Switches to Defrost in MAX Mode in 92-96; "...Well you can physically move the lever to see if the actuator (Miesk5 Note, it is the Vacuum Control Valve) is locked up for starters. And then you can start the truck (to get a vacuum source), and run a new line from a known vacuum source to the actuator."
Source: by Dan50 at FSB
A/C Switches to Defrost in MAX Mode; "...If MAX A/C only blows out the defrost registers, or if it switches to defrost during hard acceleration, this vacuum line (to the recirculate motor) is the reason. The white plastic is far more susceptible to UV light than any other color, and the gap along the edge of the hood allows it to degrade..."
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
A/C Switches to Defrost in MAX Mode; "...noticed was the white tube that connects the AC was missing. I searched around and found it was disconnected. I cut the line and reaatached it and the AC works great..."
Source: by seth15c at FSB
Air Conditioning & Heater Vacuum Diagram in 92-96; "...80-91 similar, except 87-early 88 w/factory air; The 80-86 vacuum tank is a plastic ball on the R wheelwell..."
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
Air Conditioning & Heater Vacuum Diagram in a 95
Source: by Chilton
ALL of our trucks have vacuum motors for the distribution doors exactly like Rob's diagram, EXCEPT '87-early 88 (and mine because I swapped that style in). Only those 2 years used a cable going to a compound lever for the distribution doors. ALL use vacuum for the recirc motor & ALL use cable for the temperature blend door
Source: by Steve83 (Steve, That dirty old truck) at FSB
Control Assembly Connector Location, Behind Instrument Panel Diagram in a 96, Page 2
Source: by Ford via Chilton
Control Diagrams & Overview in 78-79 & 73-79 F Series
Source: by Ford via Broncobill78 (Dave) at Ford Bronco Zone Forums
Control Overview in 80-86; "Off- Vacuum is applied to da Outside Recirc Door Vac Motor, closing that door to outside Air. Normal A/C - Outside-Recirc Door is open to outside air. The panel door directs air to the instr panel registers. The Temperature Control Lever moves a cable connected to da Temp Blend Door that mixes heated & un-heated air In Defrost Mode; with No vacuum to any vacuum "motor" (cannisters looking thangs), air Flows to Defroster outlets (& air compr clutch is engergized) Vent - Outside-Recirc Door is open to outside air, as in Normal A/C. Vacuum is applied to the Panel Door Vacuum Motor, letting air flow only to the instr panel registers. In the same way, the defroster outlets are closed by the Floor/Defrost Vacuum Motor. Floor - The Outside-Recirc Door is Open to outside air. With No Vacuum at the Panel Door Vacuum Motor. The Panel Door directs air to the floor outlets. Mix - Vacuum is applied only to Port A of the Floor/Defrost Vacuum Motor positioning the Floor/Defrost Door at mid-position. Air Flow is split between the floor & windshield. There is no vac at the Panel Door Vacuum"
Source: by miesk5 at FSB
Control Panel Diagrams & Overview in 92-96; "...In the OFF position, all doors are in the vacuum-applied position with the exception of the PANEL door. The blower & compressor clutch circuits are not energized. In the MAX A/C position, all vacuum operated doors are in the vacuum position. A/C damper inlet door (19C802) air is shut off and the passenger compartment air is recirculated to maximize cooling. Discharge is through panel register. A/C clutch & blower circuits are energized. In the NORM A/C position, outside air is allowed to enter the passenger compartment. The air passes through the A/C evaporator core (19860) and is cooled before reaching the passenger compartment. Discharge is through panel register. A/C clutch & blower circuits are energized. Ventilation is delivered through the instrument panel registers when the function selector knob in the A/C control (19980) is set in the VENT position. In the VENT position, no vacuum is applied to the OUTSIDE/RECIRC. vacuum control motor (18A318 ) and the door is open to the outside. The air coming in through the cowl is discharged through the panel registers. The blower circuit is energized, but the A/C clutch is not. In the FLOOR position, no vacuum is applied to the vacuum control motor and the OUTSIDE/RECIRC. door is open to the outside. Air is discharged through the heater outlet floor ducts (18C433) with a small amount going to the windshield defroster hose nozzles (18490). The blower circuit is energized, but the A/C clutch is not. In the MIX position, outside air is discharged through the windshield defroster hose nozzles and the heater outlet floor ducts. A/C clutch & blower circuits are energized. In the DEFROST position, outside air is discharged through the windshield defroster hose nozzles with a small amount going to the heater outlet floor ducts. All doors are in the no vacuum position. A/C clutch is engaged in ambient temperatures above approximately 10�C (50�F) & the blower circuit is energized. The PANEL/FLOOR, FLOOR/DEFROST and OUTSIDE/RECIRC doors are vacuum operated. For maximum cooling, the temperature knob should be set in its fully counterclockwise position; the function knob should be in the MAX A/C position; and the blower motor (18527) should be set for a desired rate of airflow. Even though the function knob is on MAX A/C, the temperature knob, being manually controlled, may be set to modify the temperature of the air and the path through which the air flows. Another characteristic of the MAX A/C setting is the increased noise level of the blower motor. Speed does not change when the OUTSIDE/RECIRC. door is moved to either of its two positions. The difference in noise level is that an open recirculation door exposes the passenger compartment directly to the noise. When insulated against the noise with the recirculation passageway closed, the speed appears to be less. The control knob operates an A/C switch that is attached to the backside of the A/C control by one screw and retainer tabs. Five hoses (black, white, red, blue, yellow) extend from the A/C control just below the electrical connector for the mode selector switch to the vacuum control motors and vacuum supply. The solid black hose goes to the vacuum supply through a tee-shaped A/C vacuum check valve (19A563), which attaches the A/C vacuum reservoir tank and bracket (19A566) and engine source. The white hose actuates the OUTSIDE/RECIRC. air door two-position vacuum control motor. The blue hose actuates the FLOOR/PANEL air door two-position vacuum control motor. The red and yellow hoses actuate the FLOOR/DEFROST three-position air vacuum control motor. Each end of each hose slides onto the nipple of the vacuum port to which it attaches..." SEE DIAGRAMS
Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net
Control pics in a 78
Source: by Indybronco (Lula Mae) at SuperMotors.net
Controls Overview in an 83 from Owner's Manual
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
Controls Overview in an 86 from Owner's Manual
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
Defrost Seal Nozzle & Demister Seal Location in Parts Break-Out Diagram in 92-96 w/ Nomenclature
Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net
Duct Parts Break-Out Diagram in 92-96 w/ Nomenclature
Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net
Duct Pic in 96 Bronco. Fits all 92-96 F-Series & Bronco
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
Electrical and Vacuum Troubleshooting Manual (EVTM) for an 86 (Partial); Speed Control on pages 135-139, A/C & Heater on pages 140-145, Radio on pages 127-129
Source: by Chris B (Blue, bronco boy) at telus.net
Floor Panel Door, Temperature Blend Door (Cable Controlled), Floor & Defrost Door etc. Diagrams 96 Bronco from Workshop Manual
Source: by Ford via miesk5 at Ford Bronco Zone Forums
Floor Panel Door, Temperature Blend Door (Cable Controlled), Floor & Defrost Door etc. Location w/Vacuum Line Colors in Parts Break-Out Diagram in a 96 from Workshop Manual
Source: by Ford via thedieselstop.com
Symbols in Wiring Diagrams
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
Temperature Blend Door/ Control Cable Location pic for 92-96 Bronco & F Series pic
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
Vacuum Circuit, Floor Panel Door, Temperature Blend Door (Cable Controlled), Floor & Defrost Door etc. Diagrams in a 96 from Workshop Manual
Source: by Ford via thedieselstop.com
Vacuum Control Valve Depiction in 92-96
Source: by miesk5 at FSB
Vacuum Control Valve Location in Parts Break-Out Diagram in 92-96
Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net
Vacuum Leak Test; On an idling engine check for vacuum leaks using a mechanic's stethoscope with the probe removed, or a ~3' garden hose section. Don't spray flammables on a running engine. MIESK5 NOTE; Also check: vacuum hoses; intake manifold gasket & throttle body; PCV line; vacuum reservoirs: EGR Sys Vacuum Tank & 2ndry air (coffee can); AC, heater, defroster, vent control ckt & vacuum tank (plastic ball type), under dash & lines to heat/blend/etc. doors; power brake booster; cruise control ckt, etc.... where applicable; (combined w/ Steve83's info, thnx) BEWARE OF BELTS/PULLEYS, FAN AND HOT ENGINE
Source: by miesk5 & Steve83 at Ford Bronco Zone Forums
Vacuum Line (Hose), Mini-Tube Damage Repair in a 92
Source: by JohnMcD348 at FSB
Vacuum Line Harness Pic in 80-96; "...80-96 similar, except 87-early 88 w/factory air; The 80-86 vacuum tank is a plastic ball on the R wheelwell..."
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
Vacuum Line/Hose, Mini-Tube Service in Climate Control System in a 96; "...Measure the length of the damaged area of the mini-tube vacuum hose. Cut a piece of standard 3mm (1/8-inch) ID vacuum hose approximately 25mm (1 inch) longer than the damaged area of the mini-tube vacuum hose. Cut the mini-tube vacuum hose on each side of the damaged area and remove damaged portion of the mini-tube vacuum hose. Dip the mini-tube hose ends in Tetra Hydro Furan (THF) or Methyl Ethyl Ketone (MEK). Either of these solvents will act as a sealer for the repair of the mini-tube vacuum hose. Insert the ends of the mini-tube vacuum hose approximately 9mm (3/8 inch) into the ends of the standard 3 mm (1/8-inch) ID replacement vacuum hose. Shake the service joint after assembly to make sure solvent is dispersed and vacuum line is not blocked internally. Test system for a vacuum leak in area serviced..." from 1996 F-150, F-250, F-350, F-Super Duty and Bronco, F-Super Duty Motorhome Chassis Workshop Manual
Source: by Ford via thedieselstop.com
Vacuum Line/Hose;"...The vacuum hoses used in the passenger compartment control circuit are constructed from PVC plastic material. The vacuum hoses used in the engine compartment are constructed of Hytrel. Because of the materials used, the vacuum hoses should never be pinched off during diagnosis to locate a leak. Use Rotunda Vacuum Tester 014-R1054 or equivalent to locate vacuum leaks. A wood golf tee can be used as a plug when it is necessary to plug one end of a vacuum hose for leak test purposes..." from F-150, F-250, F-350, F-Super Duty and Bronco, F-Super Duty Motorhome Chassis Workshop Manual
Source: by Ford via thedieselstop.com
Vacuum Motor Replacement in a 90
Source: by 90bronco at Maritime Off-Road
Ventilation Duct, Under Dash Diagram for 80-86; "...Pull the glove box &/or radio &/or HVAC control panel so you can look inside the dash & observe the vacuum motor & diverter door lever...If you have an 87-early 88, it's all cable (except the recirculate motor under the hood..."
Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net
Wiring Diagram in an 84 (diagram #3)
Source: by toddcomputer.com