Hot/Cold knob not moving

[MH77280Z]

Hi guys,

My hot cold knob at the center console is stuck. It is in the middle and when I try to push it towards the right hot point it just springs back, it seems like the flap or door whatever it moves is stuck. 
 

I have the center console arm rest out and want to see if I can get it fixed while I have it out. 

what should I check and can it be fixed easily without removing too many things. I don’t believe it is a vacuum issue. It is just a mechanical thing stuck I believe? Any help greatly appreciated…

[SteveJ]

It could be the watercock at the heater core. I sprayed mine down with silicone lubricant while I worked the slider back and forth. It moves smoothly now.

[Zed Head]

I had that problem.  The control wire is bent.  Somebody moved it too fast or it was stuck in the sheath and they forced it.  Take it apart and you'll see.  If you're careful you can straighten it out and it will work again.

Edit - actually I just remembered that I bought a new piece of wire at the hardware store and bent the ends to make a new control wire.  The straightened wire worked but it wasn't smooth when the fixed bent part entered the sheath.  Still had a small kink in it.

Edited May 7, 2022 by Zed Head

[MH77280Z]

The wire seems ok to me. It is not bent. The place where it hooks into is stuck. What is that part? I will be looking at it a bit more closely tomorrow during daytime and take pictures. It is some sort of module.

[S30Driver]

As Steve said, it is connected to the watercock, as the slider is moved, it opens or closes the flow thru the heater core.

Edited May 8, 2022 by S30Driver
spelling

[SteveJ]

Which end? If it's the end away from the panel, it's likely the water ****. See if you can take a picture.

https://www.totalzparts.com/product/datsun-260z-280z-heater-water-****-control-valve-1974-081975-nos-oem/

https://zcarsource.com/rebuilt-vacuum-heater-****-for-heater-control-valve-for-the-1974-78-starting-in-august-of-1973-datsun-260z-and-280z/ (AC version)

[MH77280Z]

10 minutes ago, SteveJ said:

Which end? If it's the end away from the panel, it's likely the water ****. See if you can take a picture.

https://www.totalzparts.com/product/datsun-260z-280z-heater-water-****-control-valve-1974-081975-nos-oem/

https://zcarsource.com/rebuilt-vacuum-heater-****-for-heater-control-valve-for-the-1974-78-starting-in-august-of-1973-datsun-260z-and-280z/ (AC version)

Yes end away from the panel. I will post some pics shortly.

[Zed Head]

On mine, the bent part was right behind the knob itself.  Behind the panel.  You have to remove the panel to get to it.

[Zed Head]

Borrowed this from an eBay ad.  Can't remember exactly which one but this was the location.

[Namerow]

Just to clarify what SteveJ, S30Driver and ZedHead have said, you most likely have two issues:  1) your water control valve is seized; 2) with the result that your 'TEMP' control cable wire has bent at the point where it connects to the control lever.  If you have an early car ('Series 1'), this is almost certainly what's happened.  Some pix and comments follow:

• The control cable wire for the early Z's ('Series 1') was undersized (1.0mm dia) and therefore prone to bending if anything in the assembly got stuck or balky.  In later versions ('Series 2', etc.)  the cable diameter was increased to 1.2mm.  The cable sheaths were upsized to match.
   
• The Series 2 design incorporated numerous other detail changes to the heater control system's mechanicals in an effort to make it more robust:  revised lever frame, levers, and finish knobs; revised control cable wire ends (loop-over-peg).
   
• Lawn mower control cables can be a good replacement.  Alternatively, try tempered-steel 'piano wire'.  Otherwise, non-tempered wire from the hardware store will probably be ok, unless something gets stuck again and you try to operate the controls at sub-zero temps.
   
• Unfortunately, your water control valve and/or its actuator lever have probably seized.  The probable reason is that the valve has a leaky seal. White stains on the outside of the heater plenum box are a clue.  NAPA (but not Nissan) used to offer a replacement seal, but it's been NLA for years.  So, if your water control valve is leaking you'll need to buy a complete new control valve.  If you don't fix this problem, the old valve will leak coolant onto the floor whenever it's left in the 'COLD' position.  Also, the actuator lever will probably start to stick again, too.
   
• I suspect that problems with the water control valve stem from PO's who run their cooling systems filled with straight tap water.  A stuck water control valve responds nicely to an overnight soak in a de-liming product like 'C-L-R'.   If the seal is ok, then you may be good to go. However,
   
• The older-design water control valves were said to also suffer from internal leakage, leading to a situation where the valve isn't able to fully block coolant flow even when it's set to the 'off' (cold) position.  That certainly wouldn't help if you plan to drive a Series 1 car on hot summer days. 
   
• Make sure you also free up the water control valve's actuator lever.  Lubricate its pivot pin and grease the sliding surfaces.
   

These are some pix that I took when rebuilding the Heater system for my Series 1 car:

 

 

Below:  Top side of Lever Assy
Note: Control cable on the left side (TEMP) had been removed when this photo was taken)

Below:  Bottom side of Lever Assy (photo #1 of 2)
Note:  The bottom control lever (DEF/ROOM) and the associated left and right bellcrank plates had been removed before this photo was taken)

Below:  Bottom side of Lever Assy (photo #2 of 2)
Note:  In this photo, the DEF/ROOM control lever, bellcrank plates, and cables are in place.  However, the control lever's centre actuating pin had snapped off so the bellcrank plates had nothing to engage with.


Below:   Water Control Valve, c/w actuator lever assy (actuator cable has been removed)
Note:  Control valve's actuator rod can be seen here.  Actuator lever may need to be freed up and lubricated if it, too, has become frozen because of corrosion.


Below:  Water Control Valve's actuator lever assy
Note stains.  Presumably caused by leakage from the Water Control Valve.  They look like calcium deposits.  If they are, then my car's cooling system must have been filled with straight water at some point (probably during the time when it lived in New Mexico).

Below:  'TEMP' actuator cable with bent wire (photo #1 of 2)
Note:  Here, the cable is fully extended and the bellcrank has been rotated about 45 degrees CW from its centred position.

Below:  'TEMP' actuator cable with bent wire (photo #2 of 2)
Note:  Here, the cable is fully retracted, but the bellcrank has not been rotated CCW any further than its centred position.

 

Edited May 8, 2022 by Namerow
add photos

[MH77280Z]

Ok u guys are right.

there are 2 wires connected to this dash knob. The silver thicker one goes to this orange module. What is this orange module?

also there is a thinner wire in the black wire sleeve that probably goes to the watercock. It was bent. I held it with my hand and moved the lever and it did moved back to the cold. So it is a thinner wire and needs replacement.

Also while I pulled the old carpet out I noticed a slight coolant in the front passenger bay towards the rear? So what does it mean? I have a leak somewhere? Will moving the knob to cold prevent further leaks? If I left it like this.

pardon me if my understanding is a bit weak and I am repeating something.

 

[MH77280Z]

Correction water was under the seat in the rear passenger area and I did not notice much in the front pan. May be some moved to the back while the old carpet absorbed some.