weak airflow through hvac system...in an 84

[Wishmeluck]

84 Bronco... blower motor is new and has all 4 speeds, the vacuum lines and diaphrams are all working as they should. I have hot, cold, and everything in between air temps. Ive also pulled the dash and fixed the big vent door by the heater core that breaks, installed a new heater core...basically most everything is new. But for the life of me, I can not seem to figure out why the air flow the blower motor puts out is so weak that even on high the air doesnt reach far enough to defrost the entire (or most) of the front windshield.

The last time I removed the blower motor to check if the squirrel cage was spinning correctly, I did notice that the air flow is generated only towards the back (closest to the motor) portion of the squirrel cage. Seems like it should be generating air the entire width of the cage, should it not?

Am I missing something? Any other ideas? Upgrades?

Thanks

 

[miesk5]

Yo Wishmeluck,
Welcome to out Bronco site!
Here is some information for you;
1986 Ford Bronco Sales Brochure




●From 1986 Electrical & Vacuum Troubleshooting Manual - Gary's Garagemahal (the Bullnose bible) by Ford via Gary


86 Section 1 - Emission Control ID & Application

86 Section 3 - Emission Related Components

86 1986 Engine & Emissions Diagnosis

1985-1986 Fuel System Adjustments by Ford via Gary

1986 Bronco Operating Guide by Ford via Gary @ 1983 Ford Bronco Manuals & Pamphlets (Scanned) picture | SuperMotors.net

1986 Owner Guide by Ford via Gary

1986 Exterior Colors by Ford via Gary

1986 Bronco Accessories Catalog by Ford via Gary. @ 1986 Ford Light Truck Accessories Brochure

1980-86 Pickup Fasteners by Ford via Gary, but mostly for front clip

1986 Bronco Rapid Specs Guide by Ford via Gary @ 1986 Ford Light Truck Accessories Brochure

1986 Color & Trim Selection Options by Ford via Gary

Haynes Red Manual for 80-95 Bronco & F Series @ Hanes guide 80-96 bko f series.pdf via member BroncMom!

See my mostly recovered site by member schwim @ Ford Bronco And F-150 Links - FORD BRONCO
It contains boo-koo component repairs, installation & parts sources.

See this Index of /Bronco/Projects in an 86 by my friend Chris B @ Index of /Bronco/Projects

 

[Wishmeluck]

Thanks Miesk. The issue isnt hot/cold, different speeds, or air not switching from vent/defrost/floor. Its an air volume issue. The only thing that isnt new is the interior/exterior hvac box itself. Ive replaced literally everything else. Its almost as though the space the air is required to flow though is so large that the volume of air the blower motor is capable of putting out simply isnt enough to create adaquate flow. Does that make sense?

 

[miesk5]

Yo Wishme,
Due to illness in my family all that I can offer for now is:
Not Much or No Heat in an 86; "...You should check the blend door to see if it's switching to hot. If you pull the glove box out, you can see the cable going to it on top of the ductwork as you move the slide. If it has NO resistance or if it binds, then the door might have broken away from its film hinge..."
&
Blend Door Replacement in 80-86; "...the air coming thru the heater core was hot. Now you're saying it's cooler by the time it makes it to the dash registers??? The only way for that to happen is for it to mix with cooler air in between. The most likely spot is at the temperature blend door (shown in that diagram). If it doesn't FULLY close off the cold side, you'd feel hot air if you remove the cover behind the glove box, but it would be cooler at whatever register you select (floor, dash, defrost). You have to pull either the heater core or the evaporator core to see the blend door. Obviously, the heater core is easier, but you don't have to open the A/C system to pull the evap. out..."
&
Door Locations pic in 80-86 w/Dash dropped; "...After lowering the column, removing the big Aluminum casting, unbolting the 2 large connectors under the brake booster & releasing them from the firewall, the 3 connectors in the R kick, & the green ground ****** there are four 7mm (T15) screws along the w/s, an 8mm (5/16") at the R end, and two 8mm screws at the brace bars above the tunnel, and the dash flops onto the floor. Then the vacuum lines, HVAC cables, & antenna cable can be released, allowing the dash to come out..."
&
Blend Door Location in a 94; 80-96 similar; "...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...."
&
Overview in 80-86; "Off - Vacuum is applied to the 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 Temp Blend Door that mixes heated & un-heated air.
In Defrost Mode - No vacuum to any vacuum "motor" (cannister), 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"

All above by banned member Steve83.

Will try to be back later.

 

[L\Bronco]

84 Bronco... blower motor is new and has all 4 speeds, the vacuum lines and diaphrams are all working as they should. I have hot, cold, and everything in between air temps. Ive also pulled the dash and fixed the big vent door by the heater core that breaks, installed a new heater core...basically most everything is new. But for the life of me, I can not seem to figure out why the air flow the blower motor puts out is so weak that even on high the air doesnt reach far enough to defrost the entire (or most) of the front windshield.

The last time I removed the blower motor to check if the squirrel cage was spinning correctly, I did notice that the air flow is generated only towards the back (closest to the motor) portion of the squirrel cage. Seems like it should be generating air the entire width of the cage, should it not?

Am I missing something? Any other ideas? Upgrades?

Thanks

Hey wishmeluck,
You are definitely in the tough part of HVAC diagnosis.
I may have missed it, but do you have A/C? If not, is it the Hi output heater?
Just need to know for airflow diag.
Also, check to see if the squirrel cage is turning the right direction. (I have seen reman units that have the pigtail wired backwards. When the fan runs backwards, some air will still go through the heater box.
Look at the angle of the blades in the squirrel cage, it should rotate in the direction that pulls air from the inside - out. (Hope that makes sense)
Run it plugged in, but out of the heater box.


If you look at the wiring diagram, blk from the motor goes to orange\blk on the harness while orange from the motor goes to brown\orange on the harness.
Very easy to mix up if someone is trying to do electrical when they should be holding the light.
Hope that helps
Cheers

 

[Wishmeluck]

Thank you all for your help. I pulled off the dash and found a few small air leaks in the HVAC box so I plugged those, but it didnt really help much. I was reading another thread that Miesk had posted on about HVAC stuff and one thing mentioned was that the generic blower motor brands CFM output is lower than the original motorcraft blower motors. I'm begining to wonder if thats the issue. The new blower motor came with the Bronco when I acquired it. After some digging it appears the PO purchased the blower motor and cage from Oriellys (it doesnt specify if its for a/c equipt vehicles (which mine has), and it spins counter-clockwise...correct me if I'm wrong, but dont our blower motors need to spin clockwise?

Anyways, Im going to ditch the cheapo aftermarket, go with a motorcraft and pull a cage off a rig in the parts yard down the road.

Thanks again for your help, will keep you posted, and wishing whoever's ill in your family a speedy recovery, Miesk.

 

[Wishmeluck]

So, turns out the airflow issue was with the cheap chinese blower motor and wheel assembly. Picture below show the difference between the two for reference (black wheel is made in china, white wheel is original with new motorcraft motor). after replacement the air volume is absolutely amazing on all settings. It did require either purchasing a pigtail adapter ($60 was the cheapest I found it for) so I opted to take a field trip to my local wrecking yard. Hope this helps someone down the road and till next time....

 

[Tiha]

Great info, thank you.

Glad you got it worked out.