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96 XLT, 5.8, E4OD, Auto 4x4, Mile Marker, 4in lift with 35's
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Discussion Starter · #1 ·
Since April I have replaced the heater core, radiator, heater hoses, water pump, and thermostat (192) and now with the really cold weather I have very little heat. Used to blow really hot and now little to nothing. Heater hoses get hot, blower motor has all the settings working. I have seen a heater control valve in line on heater hoses, but my 96 with the 5.8 doesn't have one. I guess my question is does mine have a heater control valve and is it run by vacuum or is it electric?
 

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1995 5.8, 2.5" Rough Country Lift, Extended RA's, 4.10's, 33" BFG's
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These Broncos didn't come with heater control valves but some people put them on, if you have one it'll be under the hood between the engine and heater core. Does defrost get hot? Does it at least blow warm?
 
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96 XLT, 5.8, E4OD, Auto 4x4, Mile Marker, 4in lift with 35's
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Discussion Starter · #4 ·
These Broncos didn't come with heater control valves but some people put them on, if you have one it'll be under the hood between the engine and heater core. Does defrost get hot? Does it at least blow warm?
Just got in from checking the blend door as @Rob_64-365 suggested and that is working as it should. My defrost blows luke warm and not warm enough to defrost the windshield, it's also 19 degrees and starting to snow here in Pa. I guess for shits and giggles I'll change the thermostat and see what happens.
 

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1990 EB, 5.0
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How about the vacuum line for the blend door? Those things come off all the time. Five bucks say this is somehow vacuum related.
 
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Yo Tom,
No Heat/Heat: The diverter door (panel, defrost, floor) is totally independent of the blend door (hot/cold), and it's vacuum-operated, so it'll always be slow.
Probably the temp blend door is loose & flopping around on its own. The easiest way to see it is to fully lower the glove box, pull the ~8 screws from the heater core cover, & look inside to the L (driver's side). You'll see the cable & control lever (in top L of 2nd pic) as soon as you fold the glovebox down, so inspect it first. The 3rd shows the whole cover - it's the large section in the top center with tiny white numbers inked near its bottom edge. The cables are visible, too...The diverter door (panel, defrost, floor) is totally independent of the blend door (hot/cold), and it's vacuum-operated, so it'll always be slow. Concentrate on the blend door for now. pull the cover & look at it.

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
Symptom Chart — Climate Control System
CLIMATE CONTROL SYSTEM
ConditionPossible SourceAction
  • Insufficient, Erratic, or No Heat
  • Low radiator coolant.
  • CHECK radiator cap pressure. REPLACE if below minimum pressure. FILL to specified coolant level. PRESSURE TEST for engine cooling system and heating system leaks. SERVICE as required. GO to Pinpoint Test B.
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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1986 Eddie Bauer 5.0EFI AOD Full length headers Y pipe into single 3" Magnaflow 3" factory exit
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The only things I can think of are that heat blend door being broken some how, as miesk5 is eluding to, either that vacuum not working or that blend door not rotating to let air pass over the heater core. All of which you can see function if you pull the gbox out & pull the heater core cover off.

I had a lot of debris blocking the airflow on my 86, but you just had your heater core & unlike my 86, debris is less likely to get thru in the newer broncos with the smaller vent holes. There are also the possibility of mouse nests being built in there, which does happen too, but the only way you can really tell is to pull the heater core back out, and look all in the hole with it out, and while you're in there, check the function of the blend door & make sure recirculation door isn't broken leaving it to pull in fresh cold air.

It's the old Chinese proverb "Sum-ting-wong" and you're gonna have to dig in deeper till you find that something.

If the heater core hoses going into, and out of the heater core are scorching hot (as they should be) it's not your t-stat. If your coolant is clean, green, it shouldn't be all sludged up blocking flow.

I'm gonna have to still say something with a blend door not working properly, either a mechanical failure where the door broke off from the rod internally, or a vacuum line or actuator isn't working right.
 

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1995 5.8, 2.5" Rough Country Lift, Extended RA's, 4.10's, 33" BFG's
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I believe if the blend door fails the defrost should still be hot, it was a safety feature. If the heater hoses are hot then your T-stat is probably good. Its quicker and easier to remove the heater core than it is to remove the t-stat so I would check that first, they get plugged up pretty easily
 
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96 XLT, 5.8, E4OD, Auto 4x4, Mile Marker, 4in lift with 35's
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179 Posts
Discussion Starter · #9 ·
Yo Tom,
No Heat/Heat: The diverter door (panel, defrost, floor) is totally independent of the blend door (hot/cold), and it's vacuum-operated, so it'll always be slow.
Probably the temp blend door is loose & flopping around on its own. The easiest way to see it is to fully lower the glove box, pull the ~8 screws from the heater core cover, & look inside to the L (driver's side). You'll see the cable & control lever (in top L of 2nd pic) as soon as you fold the glovebox down, so inspect it first. The 3rd shows the whole cover - it's the large section in the top center with tiny white numbers inked near its bottom edge. The cables are visible, too...The diverter door (panel, defrost, floor) is totally independent of the blend door (hot/cold), and it's vacuum-operated, so it'll always be slow. Concentrate on the blend door for now. pull the cover & look at it.

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
Symptom Chart — Climate Control System
CLIMATE CONTROL SYSTEM
ConditionPossible SourceAction
  • Insufficient, Erratic, or No Heat
  • Low radiator coolant.
  • CHECK radiator cap pressure. REPLACE if below minimum pressure. FILL to specified coolant level. PRESSURE TEST for engine cooling system and heating system leaks. SERVICE as required. GO to Pinpoint Test B.
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.
Thank you @ miesk5 for the info. I pulled out the heater core again and the temperature control door is working as it should, all vacuum lines are intact. Have circulation in the radiator. The only thing I didn't check is if the heater hoses are crossed. My buddie did them as I was getting the new thermostat if I remember right. I'm going to check them when it cools down and I warm up. Thanks again for the info.
 

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Yo,
Update!
"...
  • Insufficient, Erratic, or No Heat
  • Low radiator coolant due to coolant leaks.
  • CHECK radiator cap pressure. REPLACE if below minimum pressure. FILL to specified coolant level. PRESSURE TEST for engine cooling system and heating system leaks. SERVICE as required.
  • Engine overheating.
  • REMOVE bugs, leaves, etc. from radiator and support or A/C condenser core fins. CHECK for:
    • Operation of engine fan clutchLoose drive beltSticking thermostatIncorrect ignition timingWater pump impeller damageRestricted cooling system
    • SERVICE as required.
  • Loose drive belt.
  • REPLACE drive belt if cracked or worn and ADJUST drive belt tension.
  • Thermostat.
  • FEEL heater water hoses. If the heater water hoses are too hot to hold, the thermostat is OK. If the heater water hoses do not get too hot to hold, REPLACE the thermostat. If only one heater water hose gets hot while the other remains cool, a plugged heater water hose or heater core is indicated.
PINPOINT TEST A: INSUFFICIENT HEAT
A1 CHECK ENGINE COOLANT LEVEL
  • Allow engine cooling system to fully cool and check radiator coolant level.
Is coolant level low?
YesNo
FILL and BLEED engine cooling system. REFER to Section 03-03. RETEST system.GO to A2.
A2 CHECK HEATER HOSE ROUTING AND CONDITION
  • Check that heater water hoses are not crossed or routed incorrectly. Refer to Section 12-02 for heater hose routing.
  • Visually inspect condition of heater water hoses for pinched or collapsed conditions.
Are heater water hoses in good condition and routed properly?
YesNo
GO to A3.REPAIR or REPLACE heater water hoses as necessary. RETEST system.
A3 CHECK COOLANT FLOW THROUGH HEATER CORE
  • Start vehicle and allow to reach normal operating temperature.
  • Place temperature control knob in the full warm position.
  • Grasp inlet and outlet heater water hoses. Both heater water hoses should be warm to the touch due to coolant flowing through them.
Do heater water hoses indicate coolant flow?
YesNo
GO to A4.FLUSH heater core to remove obstructions. RETEST system. If flushing does not correct condition, REPLACE heater core. RETEST system.
A4 TEST THERMOSTAT
  • Start vehicle and allow to run for 10 minutes.
  • Feel the heater water hoses and the underside of the upper radiator hose.
Are the heater water hoses and the upper radiator hose cool?
YesNo
REPLACE thermostat. RETEST system.GO to A5.
A5 CHECK TEMPERATURE CONTROL DOOR OPERATION
  • Rotate temperature control knob from full warm to full cool and check temperature door for operation.
Does temperature door operate correctly?
YesNo
CHECK for head gasket leaks. REFER to Section 03-00 for information on cylinder heads. REPAIR as necessary. RETEST system.CHECK for binding, damaged or disconnected temperature door. REPAIR or REPLACE as necessary. RETEST system.

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 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."

By Ford
 

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Maybe an air trap. Does the recovery system function as expected? Fluid rises when hot and draws down when cooled off?
 
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96 XLT, 5.8, E4OD, Auto 4x4, Mile Marker, 4in lift with 35's
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179 Posts
Discussion Starter · #12 ·
Problem solved. I have heat again! Learned a lot from the info that I was given by @Rob_64-365, @JScatt, @Siggy89, @Narve, And most of all for the GREAT INFO he always ends up sharing with us @miesk5! Turns out that the heater hose routing for a 5.8 with the E40D is opposite of what I was looking at. I may have been cold driving my Bronco for a few weeks but was worth it in the knowledge I've gained. Thank You again Guys.
 

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1991Bronco 5.8L, w/95frontclip, 6"Superlift/SuperRunner, Deaver J40 springs, 35x12.5 K&N, 3"Bassani
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Are the heater hoses hot to the touch? Could have a blockage or air after replacing the heater core.
Also, I would do a vacuum check on the lines vs jus a visual inspection.
PS>. By chance does it have the Explorer diverter valve (upgrade) connected to the heater hose. It could be a vacuum, mechanical or electric actuated valve.
 
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