Climate Control-Heater Hot Water Control Valve- Inconsistent Closure-Vacuum Signal?

[MikeC]

My climate control hot water valve is not consistently shutting off the hot water supply to the A/C box when I set the controller for maximum cooling (18 deg C).

Generally it will initially operate with the hot water valve fully closed with the 18 degree setting but if I then increase it a few degrees and then try to go back to 18 degrees the valve wont reclose. But if I switch off the engine and restart it with the CC set at 18 degrees C the valve will close again.

There should be plenty of vacuum available as I did this with the with the engine idling.

I've replaced the hot water control valve with a Gates valve , which was operating freely when tested and I've reset the hot/cold air mix doors.

Is there something I'm missing, such as a poorly adjusted microswitch somewhere that forces the hot water valve closed when maximum cooling is called up?

 

[BlackVXGTS]

18 degrees is right at the bottom of the cold range which may (or may not) have something to do with your problem. Do you get the same situation if you set the CC to 19 degrees?

 

[MikeC]

I did a few more tests and at an ambient temperature of 26 degrees the valve closed at start up and held closed until the cabin temperature was raised to 22 deg C- then it opened and wouldn't reclose when the cabin temperature was reduced again, even down to 18 deg C.

This action repeated, the valve would only close after an initial engine start, wouldn't reclose when the cabin temperature was reduced with an operating engine. The valve shut off vacuum signal may be intermittent or switched off when the engines operating I'm running the car around with the throttle cover off so I can keep an eye on the valve position.

With hot weather starting around here I want the valve to close and keep hot water out of the airbox whenever I call for maximum cooling- if that means I have to set the cabin temperature at 18 degrees C then so be it. At the moment it's looking like I will have to start with an 18 deg setting and not touch it again until I shut the engine down.. The VQ cooling system operating with modern refrigerants is marginal at the best of times.

Does anyone know if there is a micro switch (maybe on the air mix door?)that tells the climate control to shut off the hot water valve or is the valve close signal generated within the climate control module.

I've noted some desperates have locked the water valve closed with wire ties over summer but I hope I don't have to resort to that.

 

[91SS]

Not sure if statesmen set up is the same as my SS but the problem,may be related to heater not fully closed.

With my manually controlled heater dial there is a rod from back of dial to linkage on flap of heater box on drivers side next to console between it and footrest. You will see a yellow plastic retaining clip. Now that clip can be carefully opened and replaced on rod on a position on rod which fully closes heater tap in engine bay. Even if L3 set up doesn't have exact set up it may have something to do with it.

Mine wasn't closing heater valve consistently because of this, from memory switch was sometimes making sometimes not and noticed heater valve sometimes open on fully closed dial.

Remember too our models didn't have the coldest AC......and with retro fitting of newer gas they are slightly less efficient even with VP condenser.

 

[MikeC]

Not sure if statesmen set up is the same as my SS but the problem,may be related to heater not fully closed.

With my manually controlled heater dial there is a rod from back of dial to linkage on flap of heater box on drivers side next to console between it and footrest. You will see a yellow plastic retaining clip. Now that clip can be carefully opened and replaced on rod on a position on rod which fully closes heater tap in engine bay. Even if L3 set up doesn't have exact set up it may have something to do with it.

Mine wasn't closing heater valve consistently because of this, from memory switch was sometimes making sometimes not and noticed heater valve sometimes open on fully closed dial.

Remember too our models didn't have the coldest AC......and with retro fitting of newer gas they are slightly less efficient even with VP condenser.

Thanks. I found the clip/switch/vacuum line you referred to in a VP Commodore manual. There is nothing similar on the VQ CC airbox.

If the problem re appears I'll have a look at the mixing door flap motor. There might be something adjustable like that switch in it but it's a horrible bit of gear to access. I've previously set the flap motor to the fully cold position ( fully clockwise- air flap door covering the heating coil) with the 18 degree C setting on the cabin temp gauge.

At the moment I'm getting the heating valve to close fully with a cabin temp setting below 20 degrees C and the air distribution control set to vent&console or bi-level. The valve closure operation seems to be consistent as I run the cabin temp setting up and down between 18 and 32 deg C. I can live with those parameters if they stay.

I've fitted a new compressor and condensor in the past year and the airconditioning is pretty average compared with what I can remember from when I first drove the car in 1995. I used to work dairy plant Christmas shutdowns along the Murray back in those days and the VQ was a real refuge from the 40 deg C heat. Still we'll never get R12 refrigerant again, so we have to live with it.

 

[91SS]

I had mine retro fitted in 2004 after compressor o ring leaked, with a new condenser in 2009. Remember AC tech mentioning that gas fill must include orfice after modification whatever that means but yeah drop off from 1994.

Sounds like you have factory manuals. With my set up the rod actuator must activate the switch to fully close heater tap only on last click of temperature control......So your electronic set up may have something similar....may be that the fully closed tap must only occur when temperature is set to 18 degrees . So possibly with electronic set up and less efficient gas thermostat is picking up anomalies and hence inconsistent performance.

Food for thought perhaps with factory manual as a guide.

Good luck.

 

[MikeC]

I had mine retro fitted in 2004 after compressor o ring leaked, with a new condenser in 2009. Remember AC tech mentioning that gas fill must include orfice after modification whatever that means but yeah drop off from 1994.

Sounds like you have factory manuals. With my set up the rod actuator must activate the switch to fully close heater tap only on last click of temperature control......So your electronic set up may have something similar....may be that the fully closed tap must only occur when temperature is set to 18 degrees . So possibly with electronic set up and less efficient gas thermostat is picking up anomalies and hence inconsistent performance.

Food for thought perhaps with factory manual as a guide.

Good luck.

Thanks. I've had at least one orifice tube replaced in the last 10 years - they have a strainer incorporated in them from memory which I thought might be blocked -I assume the replacement orifice tube was selected for the current gas (probably 134a at the time).

It could well be that the different gasses and component age have allowed the original CC computer settings to drift. A manually operated microswitch like you have that could be adjusted to definitely close off the heater valve and would be nice but I don't think one exists in the VQ CC system.

I've even contemplated putting a manual ball valve in the long heater hose above the injectors- and shutting it off for summer.

I do have a set of factory manuals and if the heater valve closure problem persists I'll have to plug away looking for solutions. There is no excess cooling margin in the VQ to cover any hot air leakage past the mixer doors.