heater levers

[abyars111]

I rebuilt by heater box and reinstalled it. I'm having trouble comprehending the heater & defrost cables. There are two cables on the bottom control lever, one is for the heat/defrost flapper the other closes the flapper in front of the blower wheel. When I move the lever to defrost the cable for the defrost door barely moves. It doesn't seem enough to divert air. This is on a non A/C fresh air heater. To clarify my problem, the heat/defrost cable seems to not move and all the pivoting action is on the other cable. Is there a pivot point for the bottom leaver that can break? I connected everything and the lever want move all the way to defrost.

On another note why did Ford put the second door that blocks air flow from the blower or does it work in conjunction with the defrost door to direct air flow?

[KRob]

Yes Yes, I am interested too. Mine after taking the heater box out to lay insulation isn't working well either.

[sargentrs]

Sure you've got the correct cables on the correct diaphragm? Never thought about this before but as I understand it, the heat/defrost lever just connects to the large flap to direct air flow to either the floor vent or the defrost vent or someplace in between. The heat/cool lever operates both the smaller flap and the heater control valve in the engine compartment. The only logic I can figure for that is that when you move the lever to "hot", the water valve opens to allow flow through the core and the flap opens to allow the fan to push it. When it's in "cool" position, the water valve closes and the flap closes to negate any residual heat from the heater core. However, that would totally disable air flow from the fan to reach the floor/defrost vent. That implies that the only time the fan is pushing air is when you're in "heat" mode? That explains why the kick panel vents open up directly into the cab. I vaguely remember thinking (my truck's been apart over 2 years now) that something must be wrong with my air flow because it seemed like the only time the fan was pushing air was when the heater was on. Looks like it was designed that way? http://www.fordification.com/tech/image ... heater.jpg Looking at the top left diagram of the controls cable #18518 and #18552 are both connected to the same lever. In the center of the diagram, cable #18518 goes to the heater control valve and #18552 goes to the small flap in the box. So, cable #18548 goes to the heat/defrost lever. Am I wrong?

[abyars111]

that's what I thought when I took the box apart but after looking at my levers the top lever is for hot cold only the bottom lever is for defrost & air flow, it is strange

[abyars111]

I should have taken pictures when I had it all apart yesterday. Check out Keith's pictures on this link http://www.fordification.com/tech/AC-cables.htm

These pics are for a A/C truck but the only difference is the top lever has two cables, the bottom lever is the same and serves the same purpose. I'm dealing with cables 3 &4 in his pics.

[Art]

On a heater box without AC:

The upper lever controls to the heater hose control valve in the engine compartment, so it operates a single cable that is passing through the firewall. If that lever does not operate smoothly mark where it was attached to the valve, disconnect it from the valve and try the upper lever again. If it moves freely, the valve may be sticking or stuck.

The lower lever usually is more of a problem. The bottom lever moves two cables, both of which go to the heater box. One cable controls the shutoff flapper (to turn the airflow, i.e. heat, completely off) and the other cable controls the flapper that directs the airflow up to the defroster or down to the floor outlet. I would make note of which cable goes where and then disconnect both of them. Then see if the bottom lever moves freely.

From my experience, I have found that the heater control cable routing can also affect how the cables move. The cables do not like tight radius bends, and work much better when routed so that the path and turns are as smooth as possible. I also like to oil the cables to make them operate easier and prevent rust.

Over 40+ years of time, it is very possible that somewhere along the line someone changed them around, kinked them, or who knows what...

[abyars111]

Thanks. I'm now suspecting the defrost cable. I replaced the air flow cable but not the defrost cable. I will disconnect them both and see how the lower lever moves. Thanks.

[F100 Dad]

I just rehabbed my system and found lubrication makes everything work much better. Two of my old cables had gotten so hard to move that the PO broke the ends off of 2 of the 3 cables.

Get yourself a "cable luber" (under $10 shipped on flee bay) and a can of Blaster brand dry graphite lube from Home Depot. It sprays as a liquid and then evaporates leaving the graphite behind.

Lube up all the cables from both ends. I also hit pivot rods in the heater box, the edge of the metal defroster diverter "door", and the slot in the top of that the rod moves in. I also used some on the lever pivots and roller wheels. Lastly, check your control valve to make sure it isn't bound up.

I am still thinking about what I might do address moisture getting in the control valve/engine compartment end of the temperature control cable.