Keep Bending Heater Cable - Need Routing

[Hardway]

I pulled my heater control panel to fix this problem.  As I was reinstalling it I was making sure the cables and controls operated as expected.  I went to test this and BAM!  It bent again with little effort.  This is the cable that goes on the lower right side of panel to the vent door above the blow motor.  The door opens and closes freely and it has its spring mounted but the pushing action on the cable keeps bending it.  Before I buy any new parts can someone post up the routing of the control cable?  Maybe I am putting too many curves in it causing a build up of pressure.  Thank you!

[Patcon]

Has that cable bent before? If it has bent previously it becomes weaker and easily bent again...

[Mikes Z car]

For sure it would be weaker IMO.  I took the liberty of zooming in for a closeup and notice there is metal wear on the lever arm, I wonder if it could be bent away from the frame it is rubbing on if that makes sense?  The lever arm would need to be bent away from the viewer just a little as viewed in your picture.

 

Edited October 31, 2016 by Mikes Z car

[Zed Head]

I made a new cable from hardware store piano wire.  The hardest part is cushioning the edges of a pair of pliers so that they don't nick the steel when bending the ends.  If it nicks, it will break instead of bending.

[Hardway]

The cable has been bent before.  This would be the 3rd time I have fixed it.  I see the wear marks and I could try prying the arm away but I don't think that is my problem.  The action of level itself is smooth.  I think I am either routing the cable wrong or just need to buy a new one if it has indeed been weakened.

[Namerow]

6 hours ago, Hardway said:

The cable has been bent before.  This would be the 3rd time I have fixed it.  I see the wear marks and I could try prying the arm away but I don't think that is my problem.  The action of level itself is smooth.  I think I am either routing the cable wrong or just need to buy a new one if it has indeed been weakened.

A few thoughts:

1. Is there any chance that the previous owner replaced this cable with non-tempered wire?  If so, it will remain prone to bending like this.  How easy has it been for you to straighten the wire previously?  If your answer is, 'easy', then my level of suspicion would increase.  Like Zed Head, I made my own replacement set of cables using tempered 'music' wire.  Not a hard job, really.  I formed the ends by hammering the wire to shape over the jaws of my bench vise. 
    
2. Even if the bent wire is made from tempered stock, the fact that it's now been bent and straightened three times at the same spot may have softened or weakened the metal at the bending point (meaning that it's pooched and will never perform properly).  Metallurgists, feel free to comment.
    
3. Not sure what vintage of Z you're working on, but be aware that there was an earlier style of heater control mechanism that used thinner-gauge (1.0mm) control wires.  They didn't prove up to the job and tended to bend if there was any extra resistance in the system (due to corrosion, parts, interference or even, perhaps, mis-routing).  The re-designed system used 1.2mm wire (along with loops rather than straight-wire-and-a-pinch-screw used to secure the device end).  Note that the pictures below show the early design with the skinny control cables.
    
4. A sticky control lever shouldn't cause the load on the cableto increase.  The problem has to be friction or interference downstream of the control lever (or an under-spec wire).

 

For your possible interest/amusement, here's how my Series 1 assembly looked when I took it out of the car.  The culprit here was a frozen heater control valve (and an impatient driver or passenger who was clearly not happy with the cabin temperature!).

x

 

Below are the best pictures I have to show the original routing of the control cables.  These were taken as the assembly was being removed from the car as part of stripping the interior.  Unfortunately, for the cable that you're having trouble with they only show the end sections and not much of the middle part (notice that the device end of the cable where it mounts to the flap lever doesn't look to happy -- which may help to explain why the factory revised the device ends of the cables to a loop-over-peg design). 

x

Looking in ^
 

Looking up ^

This final picture, showing the complete assembly lying on the floor of my workshop, may give you some additional clues about the cable routing.

[Hardway]

Thank you Namerow for all the info and pictures.  My car is a 8/70 build 1971 240z series-1.  When I bought it none of the controls worked right as a previous owner had installed some cables that looked like generic choke cables from the auto parts store.  The current set of cables I have are used.  I picked them up from one of the mass parts sellers on Ebay.  Looking at the last picture you posted, I have my super long cable on the bottom right hand side when the controller is sitting the way yours is.  I thought the top RHS cable went to the hot water valve and the bottom went to the air flap door above the blower.  Is this how yours is set up?

[Hardway]

Another thought.  If I buy a new cable from MSA, it will be stronger correct?  What about using a different cable like from another classic car or motorcycle?  Taking the heater panel out is a huge pain and I would like for this to be the last time if possible.

[Namerow]

23 hours ago, Hardway said:

Thank you Namerow for all the info and pictures.  My car is a 8/70 build 1971 240z series-1.  When I bought it none of the controls worked right as a previous owner had installed some cables that looked like generic choke cables from the auto parts store.  The current set of cables I have are used.  I picked them up from one of the mass parts sellers on Ebay.  Looking at the last picture you posted, I have my super long cable on the bottom right hand side when the controller is sitting the way yours is.  I thought the top RHS cable went to the hot water valve and the bottom went to the air flap door above the blower.  Is this how yours is set up?

Hmmm...

The diagram in the FSM Supplement suggests we both may be wrong.  Here's the FSM diagram (Series 1) and parts names...

Lower Right - 41 - Temperature

Lower Left - 42 - Room-Defrost

Top Right - 43 - Compartment Air

Top Left - 44 - Hot Water Valve

 

Maybe I'm mis-reading the number labeling on the diagram, but I think it's wrong (or the parts numbering has been jumbled in the parts name list (not shown here).  The Owners Manual clearly identifies the control knob functions as:

Top Knob - 'Air flow control for heating or ventilating'

Middle Knob - 'Air temperature control'

Bottom Knob - 'Air flow control for room heating or defrosting'.

Therefore, I don't understand how the FSM diagram manages to assign Cable #44 ('Hot Water Valve') to the top lever.

 

Perhaps someone else can comment.  Which cables go where? 

Edited November 1, 2016 by Namerow
diagram added

[Hardway]

I am so glad you said this Namerow because I have stared at that same diagram in the FSM and thought the same thing.  Hopefully some more owners can post up with what they have.  In the meantime, I am planning to go to Grainger today and see what I can find regarding control cable alternatives.  I know MSA sells new ones but there maybe something else out there that will do better and I can pick it up today.

[sweatybetty]

22 hours ago, Hardway said:

Another thought.  If I buy a new cable from MSA, it will be stronger correct?  What about using a different cable like from another classic car or motorcycle?  Taking the heater panel out is a huge pain and I would like for this to be the last time if possible.

if i were in your shoes, i would buy the cables from msa and be done with it. they should be the correct wire type and fit like factory

[Hardway]

It appears MSA is sold out of the long In/Out control cable.  Something else I am seeing, in the pictures it has a loop that goes around the connection point on the in/out door.  However, mine has a screw and threaded barrel with a hole in it to accommodate the end of the cable to be inserted and tightened with the screw.  (Just like in the picture Namerow posted)  I am assuming/hoping this means the loop will go around the outside of the barrel and I can put a small washer on the screw to prevent the cable loop from slipping off.

Edited November 1, 2016 by Hardway