Bronco Forum - Full Size Ford Bronco Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Hi, I've checked a few threads on the heater/ac blend doors etc. but my problem seems to be different. I can hear the air trying to force the door open... then close... then open... then close etc. etc. especially when I go over bumps. I have two ?'s -- what causes the continual open/close/open sequence and should I be able to hear the air so distinctly (I thinks it's air... almost a pipsqueak farty sound). Thanks Steve
 

·
Registered
Joined
·
4,910 Posts
Did any of the threads you read mention the white vacuum line going to the vacuum motor on the passenger side by the firewall? The HVAC controls are all vacuum controlled on the '96. Check the vacuum lines.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #3
Thanks for the follow-up. Could there be an electrical problem like a short that sends the actuator into motion? The problem manifest itself mainly when I go over bumps and when I first get in and start the Bronco.
 

·
Registered
Joined
·
665 Posts
Had the same problem on my 95. It was a rotten vac hose causing a leak. Like Mikey said pass side up by firewall. Near all the A/C crap.
 

·
Super Moderator
Joined
·
26,972 Posts
yo,
Ck for any Vacuum Leak in HVAC, Emissions, Brake Booster, Systems
Or for The temperature blend door, it is operated mechanically by a A/C temperature cable (19988) attached to the temperature control knob in the heater control; see below.

to begin w/;
The 92-96 HVAC 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.

Blend Door (Temperature Control) Control Cable Replacement in a 96; Installation: Release the glove box to gain access to the retainer clips on the plenum end of the cables. Depress protruding retainer clip and pull upward to free from plenum. NOTE: Removal of the A/C temperature cable (19988) from the heater control (18549) is easiest if temperature control is removed from the heater control. Installation: NOTE: All replacement service parts are shipped in the full warm position and must remain in full warm to permit proper alignment during installation. Cables are serviced as a complete assembly only. Route A/C temperature cable in same manner as cable removed. Position temperature control knob in full warm. Install temperature control switch in heater control and position A/C temperature cable so that all three retaining tabs and the beveled gearing is properly aligned. Be sure all components are adjusted to the full warm position. Push A/C temperature cable onto temperature control switch until it is fully seated and all retaining clips are engaged. Install heater control. Working through glove box opening, position temperature blend door in the full warm position. Align A/C temperature cable to locating post, align cable assembly hardshell positioning tab with keyed area on the heater air plenum chamber (18471) and the temperature blend door actuator post aligned with the cam on the cable head. Push assembly onto plenum until retaining tab is engaged. Install retaining bracket. Rotate the temperature control knob and check for operation of the temperature blend door.


Blend Door Repair in a 96 (has Pivots vs. earlier years that has the Film Hinge); "...When I could get my hand in through the hole, I found the blend door had fallen completely out of place because the entire top of the shaft was gone. When the door is intact it is retained by the lower end of the shaft fitting into a socket on the bottom of the plenum and a depressed area on top around the actuator servo's shaft access hole..." read more
Source: by brokenford at http://www.conceptualedge.com/blend-door/

Climate Control Assembly in a 96: "...The heater is a blend air type that receives its outside air supply from the cowl inlet. The heater control (18549) is located in the instrument panel (04320) to the right of the steering column. It includes the function control knob, temperature control knob and heater blower motor switch (18578). The heater blower housing assembly includes: Blower motor (18527), Heater blower motor switch resistor (18591), A/C damper inlet door (19C802), Vacuum control motor (18A318) to operate A/C damper inlet door, Electrical harness. The heater blower housing is installed on the engine compartment side of the dash panel. Electrical wire receptacles for the blower motor and heater blower motor switch resistor are provided on the heater plenum chamber case (18A484) and a vacuum connection is provided on each vacuum control motor. heater air plenum chamber (18471), on the passenger compartment side of the dash panel attaches to the heater plenum chamber case through the panel with an air passage between the assemblies provided through an opening in the panel. heater air plenum chamber includes the following components: Heater core (18476), Temperature blend door, Floor/panel door, Floor/defrost door, Vacuum control motors and vacuum hose harness (19C827). The vacuum control motors and their vacuum lines operate the floor/defrost and floor/panel doors. The temperature blend door is operated mechanically by a A/C temperature cable (19988) attached to the temperature control knob in the heater control. The function control knob is used to select the functional setting of the heater system. The settings are: VENT, FLOOR, OFF, MIX and DEFROST. Power is supplied to the blower motor when the function knob is in any position except OFF. Airflow Control: Outside air is supplied to the system through the cowl top grille. This air supply enters the heater plenum chamber case where the blower motor directs some or all air through or around the heater core depending upon the setting of the temperature control knob. Airflow through the heater air plenum chamber is determined by the setting of the function selector knob in the heater control. The outlets through which air may be distributed into the passenger compartment are shown in the following illustration. Temperature Control: Depending upon its position, the temperature blend door in the heater air plenum chamber directs a given amount of air through the heater core to provide a desired amount of heat. If the amount of air directed by the blend door through the heater core is reduced, less heat will be directed into the passenger compartment. Conversely, a fully open blend door, in response to a fully WARM setting of the temperature control knob, will provide maximum heat into the passenger compartment. Blower Motor Control: Three of four operating speeds (LOW, MEDIUM LOW and MEDIUM HIGH) are controlled by a heater blower motor switch resistor connected in series with three of the operating positions and the ground. The MEDIUM LOW and MEDIUM HIGH positions on the heater control are identified by dots on the control. With the heater blower motor switch in its LOW position, current flow in the ground circuit passes through three of the coils in the heater blower motor switch resistor. In MEDIUM LOW, current flows through two coils. In MEDIUM HIGH, current flows through one coil. In HIGH, current flow in the motor ground circuit bypasses the heater blower motor switch resistor to provide maximum speed. Recirculation/Fresh Air Control: The vehicle heating system draws outside air into it and distributes this fresh air throughout the passenger compartment in all positions except OFF. If the vehicle is equipped with air conditioning, outside air is distributed throughout the vehicle in all positions except OFF and MAX A/C. In these positions (OFF, MAX A/C) the A/C fresh air inlet door is in the closed position and air within the passenger compartment is recirculated throughout..."


Outside Recirculate Door Vacuum Motor (White) (Part of Vacuum Harness), also called the Vacuum Control Valve) Location in Parts Break-Out Diagram in 92-96 - this is the hose JohnD repaired as noted above by Mikey350
& hizootiemizark

Source: by Ford via Steve83 (Steve, That dirty old truck) at SuperMotors.net

HVAC Vac line colors in 92-96; (of course,a PO or shop may have replaced colored lines w/black or other colrs)
Black = from engine source to vacuum check valve & to vacuum reservoir tank & to Control Panel;
White = actuates the Outside/Recirc air door two-position vacuum control motor;
Blue = Mix (actuates the FLOOR/PANEL air door two-position vacuum control motor);
Red = Floor Flow
& Yellow = Panel, (actuate the FLOOR/DEFROST three-position air vacuum control motor).


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.
On COLD ENGINE only, use propane torch w/rubber hose attached, UNLIT or spray carb cleaner, when it gets to the the leak the RPMs will rise.
Also check: vacuum hoses; intake manifold gasket & throttle body; Tree Location pic in a 94 5.8 Source: by joelb23 at SuperMotors.net; PCV pic by Bbronco311. Vacuum Reservoirs: EGR Sys Vacuum Tank & 2ndry air (looks like a coffee can in earlier years) Depiction & Location in Parts Break-Out Diagram in a 96 w/Ford part numbers by Ford via miesk5 at http://www.broncolinks.com/gallery_i...6TABTAB5.0.jpg; Thermactor Air Bypass Solenoid (TAB, AIRB, AM1) w/Pink vacuum line & Air Bypass Valve (AIR BPV) & Thermactor Air Diverter Solenoid (TAD, AIRD, AM2) w/Yellow vacuum line & Air Diverter Valve or Air Control Valve (ACV) see my site @ http://www.broncolinks.com/index.php?index=416 & EGR Vacuum Regulator (EVR); also called EGR Vacuum Solenoid & EGR Valve Position (EVP) -
MIESK5 NOTE: EVP is used on all years except for 95 5.8L California models & all 96, they use the DPFE Sensor instead of EGR Valve Position Sensor (EVP) etc, see my site @ http://www.broncolinks.com/index.php?index=146. AC, heater, defroster, vent control ckt & vacuum tank (plastic ball, or an irregular box glued to the evaporator cover), under dash & lines to heat/blend/etc. doors; & HVAC vacuum reservoir; Vacuum Tank pic, Ford part number 19A566; on side of evaporator housing by Ford via miesk5 at FSB. Carbon Canister (Charcoal Canister, Vapor Canister, Evaporative Emission (EVAP) Canister for the Evaporative System (see http://fullsizebronco.com/forum/atta...1&d=1315917794. & Line to & the power brake booster, Master Cylinder & Booster Location pic in a 93 by Steve83

Is the Check Engine Light (CEL) on while engine is running? CEL warning indicator comes on when the electronic engine control system is not working properly. The check engine warning indicator comes on briefly when the ignition switch lock cylinder is turned to ON, and should turn off when the engine starts. If the check engine warning indicator does not come on when the ignition switch lock cylinder is turned to ON or if it comes on while the vehicle is moving, the system is malfunctioning or a previous owner or shop removed the bulb or bulb is burnt out; less likely is a bad CEL ckt. Have it scanned for Code for free at a part store or DIY; heat the engine up; idle until temp gauge is in normal range you usually see and when it warms up; shift thru all gears incl Reverse anyway. Then turn off all accessories/lights, etc. Make sure A/C is off and transmission is in Park (automatic). Do Key On Engine Off (KOEO) portion first. The engine temperature must be more than 180°F for the KOER Self-Test. Look Codes up in my broncolinks.com site using the new Search function if in a hurry today. And Post em here according to KOEO & KOER
Source: by miesk5 at FSB see HOT LINKS at http://fullsizebronco.com/forum/showthread.php?t=201323
 
1 - 7 of 7 Posts
Top