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Discussion Starter #1
question on the 96 Bronco shoukd the AC pump pretty hard. Cold air comes out but just doesn't cool the truck at all because its doesn't pump out to hard. Is that just the way it is or is it worth getting checked to see if the fan isn't working properly or maybe a bad evaporator.

Thanks
 

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96 XLT 5.8 E4OD 4in lift with 35's
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Mine was doing the same thing and I found a piece of the duct hose under the dash wasn't hooked up or came loose. I also changed the blower motor.
 

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95 Bronco, 351W, E4OD, 4.56 gears, 35x12.50x15 Patagonia MTs.
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327 Posts
Check and see if your vents actually change, or if its stuck on defrost? The vacuum lines tend to fail, both my fords had split lines going to the recirculation/MAX AC damper.

My evaporator coil was filthy, and still barely noticed the airflow increase after cleaning it. I doubt that's the issue unless it has a mold blanket in there.
 

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Discussion Starter #4
Mine was doing the same thing and I found a piece of the duct hose under the dash wasn't hooked up or came loose. I also changed the blower motor.
Did you notice a significant difference of air flow after. Like I said its cold coming out but what us coming out has no power behind it and it doesn't cool the cab at all. Also forgot to mention when idling there is a notice in how cool it is. So if sitting at a light the air turns kinda warm...once we start driving the air gets cold again.
 

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Discussion Starter #5
Check and see if your vents actually change, or if its stuck on defrost? The vacuum lines tend to fail, both my fords had split lines going to the recirculation/MAX AC damper.

My evaporator coil was filthy, and still barely noticed the airflow increase after cleaning it. I doubt that's the issue unless it has a mold blanket in there.
When you fixed the lines did you notice a difference.
Check and see if your vents actually change, or if its stuck on defrost? The vacuum lines tend to fail, both my fords had split lines going to the recirculation/MAX AC damper.

My evaporator coil was filthy, and still barely noticed the airflow increase after cleaning it. I doubt that's the issue unless it has a mold blanket in there.
When you fixed the lines did you notice a significant difference?
 

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Discussion Starter #6
Check and see if your vents actually change, or if its stuck on defrost? The vacuum lines tend to fail, both my fords had split lines going to the recirculation/MAX AC damper.

My evaporator coil was filthy, and still barely noticed the airflow increase after cleaning it. I doubt that's the issue unless it has a mold blanket in there.
Checked to see if vents change and they do not...air comes out of vents but if I switch to defrost the air still comes from chest high vents...if i change to floor still comes from chest high vents...i do t feel any air coming from floor or defrost when i switch to those.
 

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Yo Kp,
"...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

MOST COMMON LEAK is under hood, passenger side for the hose to fOutside Air/Recirculated Air Door Vacuum Motor
162541


as described here;
A/C Switches to Defrost in MAX Mode Vacuum Line Repair in a 92; "...began pulling out the tubing. To my surprise, the tubing that inside the plastic tubing was like new..." read more
Source: by JohnMcD348

Section 12-03A: Air Conditioning System, Manual A/C-Heater
1996 F-150, F-250, F-350, F-Super Duty and Bronco, F-Super Duty Motorhome Chassis Workshop Manual​
DIAGNOSIS AND TESTING
Pinpoint Tests

Vacuum Leak Diagnosis

The air handling system is designed to provide defrost when no vacuum is applied to any of the three air door vacuum control motors (18A318). 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 (small 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.
The vacuum hoses used in the passenger compartment control circuit are constructed of polyvinyl-chloride (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 Leak 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.
PINPOINT TEST A: IMPROPER AIRFLOW FROM OUTLETS
A1 CHECK SYSTEM AIRFLOW


  • Start engine and place heater blower motor switch in HIGH position.
  • Check system airflow in each function selector setting to determine which position(s) have incorrect airflow.
Is airflow from the defroster outlets for all function selector settings?
YesNo
GO to A2.GO to A13.
A2 CHECK VACUUM SUPPLY HOSE
  • Check vacuum supply hose to be sure it is connected to both the engine manifold and the A/C vacuum check valve.
Is hose disconnected?
YesNo
RECONNECT hose. RETEST system.GO to A3.
A3 CHECK VACUUM SUPPLY HOSE FOR LEAKS
  • Disconnect vacuum supply hose from engine manifold fitting and from A/C vacuum check valve.
  • Plug one end of hose and leak test with vacuum tester.
Does hose leak?
YesNo
REPAIR or REPLACE as necessary. RETEST system.CONNECT hose to manifold fitting. GO to A4.
A4 TEST VACUUM CHECK VALVE
  • Test A/C vacuum check valve for correct installation by removing the reservoir hose and the control assembly source hose (one at a time) from the A/C vacuum check valve and check for vacuum. Engine must be running for this test.

Is vacuum available at both check valve ports?
YesNo
RECONNECT both hoses. GO to A6.GO to A5.
A5 INSPECT VACUUM CHECK VALVE
  • Inspect A/C vacuum check valve for an obstruction and/or proper operation. Airflow through the A/C vacuum check valve should be in the direction toward engine (engine connection side is marked "VAC").
Is A/C vacuum check valve plugged or obstructed?
YesNo
REPLACE A/C vacuum check valve. RETEST system.GO to A6.
A6 LEAK TEST VACUUM CHECK VALVE
  • Remove A/C vacuum check valve from vehicle.
  • Connect two hoses and a tee-fitting to outlet ports of A/C vacuum check valve.
  • Connect vacuum tester to tee-fitting.



  • Pump 50.5 kPa (15 inches) vacuum on the A/C vacuum check valve and observe vacuum tester gauge reading. If vacuum loss exceeds 3 kPa (1 inch) per minute, remove A/C vacuum check valve from tester and plug vacuum hoses. Pull a vacuum with the tester to be certain hoses and tester are not cause of leak.



  • If tester and hoses do not leak, A/C vacuum check valve is cause of problem.
Does A/C vacuum check valve lose more than 3 kPa (1 inch) vacuum in one minute?
YesNo
REPLACE A/C vacuum check valve. RETEST system.REINSTALL A/C vacuum check valve. GO to A7.
A7 CHECK VACUUM RESERVOIR
  • Connect vacuum tester to A/C vacuum reservoir tank and bracket.
  • Pull a vacuum on the reservoir and observe gauge reading. Reservoir must hold a vacuum.
Does A/C vacuum reservoir tank and bracket leak?
YesNo
REPLACE A/C vacuum reservoir tank and bracket. RETEST system.CONNECT hose to A/C vacuum reservoir tank and bracket. GO to A8.
A8 CHECK SUPPLY HOSE FOR LEAK
  • Disconnect and plug BLACK supply hose at A/C control.
  • Disconnect other end of supply hose from A/C vacuum check valve and leak test hose with vacuum tester.
Does supply hose leak?
YesNo
REPAIR or REPLACE hose as necessary. RETEST system.REMOVE plug and RECONNECT vacuum hose. GO to A9.
A9 CHECK CONTROL ASSEMBLY

  • Disconnect A/C plenum vacuum harness at in-line multiple connector near A/C control.
  • Plug all vacuum hoses except BLACK.
  • Connect vacuum tester to BLACK hose.
  • Select each function position, apply 50.5 kPa (15 inches) vacuum and check for vacuum drop. Vacuum drop should not exceed 3 kPa (1 inch) vacuum per minute for any function position.
Does vacuum drop exceed 3 kPa (1 inch) vacuum per minute?
YesNo
NOTE function position(s) where vacuum drop occurs. GO to A10.GO to A11.
A10 LEAK TEST CONTROL ASSEMBLY
  • Remove A/C plenum vacuum harness from A/C control.
  • Connect vacuum tester to control assembly supply port which indicated a leak in step A9.
  • Select function position(s) noted in step A9 and apply 50.5 kPa (15 inches) vacuum after selecting each function position. Vacuum drop should not exceed 2 kPa (1/2 inch) per minute.
Does vacuum drop exceed 2 kPa (1/2 inch) in one minute?
YesNo
REPLACE function control switch. RETEST system.GO to A12.
A11 CHECK SUPPLY HOSE
  • Disconnect BLACK supply hose from A/C vacuum check valve.
  • Connect vacuum tester to supply hose and operate tester as if pulling a vacuum. If tester can pull a vacuum, hose is plugged. If tester pulls a partial vacuum, hose is restricted.
Is hose plugged or restricted?
YesNo
REPLACE supply hose. RETEST system.GO to A15.
A12 LEAK TEST JUMPER HARNESS
  • Plug one end of vacuum hose that indicated a leak in step A9.
  • Apply 50.5 kPa (15 inches) vacuum to hose and observe vacuum gauge reading. Vacuum should not drop.
Does vacuum drop?
YesNo
REPAIR or REPLACE vacuum jumper harness as necessary. RETEST system.CHECK connection of vacuum harness to A/C control for leak. REPAIR as necessary. RETEST system.
A13 EVALUATE SYSTEM
  • Repeat steps in test A1.
Is airflow in step A1 correct for each function position?
YesNo
GO to A14.GO to A15.
A14 ISOLATE LEAKING VACUUM CIRCUIT
  • Repeat step A1 and accelerate engine speed for each function position.
Does airflow go to defrost during acceleration?
YesNo
GO to A19.GO to A15.
A15 REVIEW VEHICLE HISTORY
  • Check vehicle service records for past service reports.
Did system function properly prior to this complaint?
YesNo
GO to A18.GO to A16.
A16 CHECK VACUUM HOSES
  • Check each vacuum hose to be sure it is not plugged.
Is hose plugged?
YesNo
REPAIR or REPLACE as necessary. RETEST system.GO to A17.
A17 CHECK VACUUM HARNESS
  • Check to be sure that all vacuum hoses are correctly color coded.
Are the vacuum hoses correctly color coded?
YesNo
GO to A18.REPLACE vacuum harness.
A18 CHECK VACUUM CIRCUIT
  • Check vacuum circuit for pinched or kinked vacuum hose(s).
Is a hose pinched or kinked?
YesNo
REPAIR or REPLACE as necessary. RETEST system.GO to A19.
A19 CHECK VACUUM CIRCUIT CONNECTION
  • Check each vacuum hose connection to determine if it is partially connected or disconnected.
Is a vacuum hose connection disconnected or partially connected?
YesNo
RECONNECT hose. RETEST system.GO to A20.
A20 CHECK VACUUM HOSE
  • Disconnect both ends of vacuum hose in suspected circuit.
  • Plug one end and leak test with vacuum tester.
Does vacuum hose leak?
YesNo
REPAIR or REPLACE as necessary. RETEST system.GO to A21.
A21 CHECK VACUUM CONTROL MOTOR
  • Check vacuum control motor for leaks with vacuum tester.
Does vacuum control motor hold vacuum?
YesNo
GO to A22.REPLACE vacuum control motor. RETEST system.
A22 CHECK VACUUM CONTROL MOTOR INSTALLATION
  • Check attachment of vacuum control motor to damper door.
Is motor arm attached to door or door crank arm?
YesNo
CHECK for binding or damaged damper door. REPAIR as necessary. RETEST system.CONNECT vacuum control motor arm to door and/or crank arm and CHECK operation. RETEST system.
PINPOINT TEST B: HEATER DOES NOT CHANGE TEMPERATURE
B1 CHECK COOLANT LEVEL

  • CAUTION: Engine should be fully cool before removing radiator cap. If the engine and cooling system are not fully cool, use extreme caution when removing radiator cap. Excess pressure within the radiator can result in hot coolant and steam escaping from the radiator with enough force to injure or scald persons standing near the vehicle when the radiator cap is removed. Use a shop towel around the radiator cap when opening the radiator cap. Turn the radiator cap only to the first release point. Step back and allow system pressure to release before fully opening the radiator. When system pressure has been completely released, remove radiator cap with shop towel still wrapped around the radiator cap.
  • Remove radiator cap and check coolant level.
Is coolant level in the radiator low?
YesNo
REFILL radiator with coolant to proper level. RETEST system.GO to B2.
B2 CHECK THERMOSTAT
  • Start engine and allow to run at least 10 minutes.
  • Carefully open radiator cap and observe coolant for evidence of circulation. Slightly increase engine idle speed if necessary.
Does coolant show evidence of circulation?
YesNo
GO to B3.REPLACE thermostat. RETEST system.
B3 CHECK HEATER HOSES
  • Check heater water hoses for kinks.
  • Check that heater water hoses are not crossed.
Are heater water hoses kinked or incorrectly routed?
YesNo
REPAIR or REPLACE as necessary. RETEST system.GO to B4.
B4 CHECK FOR HEATING SYSTEM BLOCKAGES
  • Start engine and allow to reach normal operating temperature.
  • Feel heater water hoses.
Do both heater water hoses become too hot to hold?
YesNo
GO to B5.If both heater water hoses become too hot to hold, GO to B5. If only one heater water hose becomes too hot to hold, a blockage is indicated. CHECK heater water hoses for obstructions. REPAIR or REPLACE as necessary. RETEST system. If heater water hoses check as OK, blockage is in the heater core. FLUSH engine cooling system. If flushing does not clear blockage, REPLACE heater core. RETEST system.
B5 CHECK TEMPERATURE CONTROL DOOR OPERATION
  • Rotate temperature control knob from the full cool position to the full warm position and check operation of the temperature control door.
Does the temperature control door operate correctly?
YesNo
CHECK drive belt for proper tension or signs of slippage and wear. REPAIR or REPLACE as necessary. RETEST system.CHECK temperature control door for a binding condition. Also CHECK the A/C temperature cable for connection to the temperature control door and A/C control. REPAIR or REPLACE as necessary. RETEST system.
 

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95 Bronco, 351W, E4OD, 4.56 gears, 35x12.50x15 Patagonia MTs.
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327 Posts
When you fixed the lines did you notice a difference.


When you fixed the lines did you notice a significant difference?
Yes, but I didn't have your symptoms either. My issue was intermittent, and the vent would redirect to defrost with the engine under load for extended periods of time. The air always blows very cold in my bronco, unless the engine bay is getting warm/heat soaked due to a lack of airflow.

My F350 has low air flow due to a failing fan, but it still blows cold. The F350 fan also makes noise, it's pretty obvious it's eating what's left of the brushes and or the squirrel cage has something in it.
 
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