Cruise control instalation and alternative parts.

[Robsey]

It will indeed be a latched function.

It is a kill switch function.

Only the Select (Increase) and Resume (Decrease) buttons on the stalk will be able to re-engage the cruise function.

And only when the clutch, park/neutral, brake light valves / switches are set or released to allow it.

[maxstu]

It will indeed be a latched function.

It is a kill switch function.

Only the Select (Increase) and Resume (Decrease) buttons on the stalk will be able to re-engage the cruise function.

And only when the clutch, park/neutral, brake light valves / switches are set or released to allow it.

So a good safety feature or not? I did Google latch function. Ended with immediate brain fade. Not the kind of details my limited brain easily absorbs.
Sorry!

[Robsey]

In wikipaedia speak.

A latching switch is a switch that maintains its state after being activated. A push-to-make, push-to-break switch would therefore be a latching switch – each time you actuate it, whichever state the switch is left in will persist until the switch is actuated again.

Such as the headlamp light switch.

Momentary switches require continuous compression. They will switch on when the user compresses the switch and will remain on only for as long as there is pressure on the switch. Once the pressure is removed they will switch off.

Such as the horn push on the steering wheel.

All the switching functions from the brake switch, vent valves, clutch switch act to turn off the cruise control, so that the driver regains full control of the throttle again.
Yes - they are all "good" safety features.

All the pedal operated switches turn off the cruise control to give you back control.

Cruise will stay off until you operate a stalk switch (set or resume) whilst you ensure that you are not operating any of the pedal switches.

[maxstu]

Im feeling a bit stupid now! Thanks for making it understandable for me. Will connect to handbrake light. I take it is a simple splice into the wire coming from G5? 

Regards
Stuart 

[Robsey]

I am suspecting not.

From what I can tell, the switches for the clutch and brake circuits are switched live.

That is, either switch will apply battery voltage to cruise control unit pin 3 when you press the pedal.

The handbrake on the other hand would be switched ground.

So I would be tempted to use a relay in that case.

Using the usual relay notation.

Pin 30 is supply voltage - you could use the wire from G2 or G5 to give ignition live voltage.

Pin 87 is switched output -
logic tells me to wire this at the junction between the brake light switch and the vent valves. As close to the vent valve as possible.

If wired too close to the brake switch, it may result in the brake lights coming on when you apply the handbrake.
Unless you fit a diode to prevent voltage back feeding from the relay to the brakelights.

Pin 86 is relay coil +
You could connect this to pin 30.

Pin 85 is relay coil -
You could connect the handbrake wire to this after the warning light, before the switch.

When you apply the handbrake, this would connect the pin 85 wire to ground, and trigger the relay.

When active, the relay will join the fused supply to the brake light circuit just before the vent valves.

I am making the assumption that applying 12 volts to the valves allows them to vent off and thus release the vacuum pressure from within the cruise actuation vacuum pipes.

[tobydog]

It will indeed be a latched function.

It is a kill switch function.

Only the Select (Increase) and Resume (Decrease) buttons on the stalk will be able to re-engage the cruise function.

And only when the clutch, park/neutral, brake light valves / switches are set or released to allow it.

So a good safety feature or not? I did Google latch function. Ended with immediate brain fade. Not the kind of details my limited brain easily absorbs.
Sorry!

If you don't understand the safety implications (latching among others), why are you investing your time in something you don't understand? Perhaps you could explain why you need cruise control?

[maxstu]

I am suspecting not.

From what I can tell, the switches for the clutch and brake circuits are switched live.

That is, either switch will apply battery voltage to cruise control unit pin 3 when you press the pedal.

The handbrake on the other hand would be switched ground.

So I would be tempted to use a relay in that case.

Using the usual relay notation.

Pin 30 is supply voltage - you could use the wire from G2 or G5 to give ignition live voltage.

Pin 87 is switched output -
logic tells me to wire this at the junction between the brake light switch and the vent valves. As close to the vent valve as possible.

If wired too close to the brake switch, it may result in the brake lights coming on when you apply the handbrake.
Unless you fit a diode to prevent voltage back feeding from the relay to the brakelights.

Pin 86 is relay coil +
You could connect this to pin 30.

Pin 85 is relay coil -
You could connect the handbrake wire to this after the warning light, before the switch.

When you apply the handbrake, this would connect the pin 85 wire to ground, and trigger the relay.

When active, the relay will join the fused supply to the brake light circuit just before the vent valves.

I am making the assumption that applying 12 volts to the valves allows them to vent off and thus release the vacuum pressure from within the cruise actuation vacuum pipes.

Thanks very much for the information. A brilliant and clear assessment. That's exactly how l like to read auto electrics.

[Robsey]

Thank-you for your kind words.

I still find the way Volkswagen do things a little confusing.

My opinion is - that as long as you have the brake pedal switch and the off switch on the stalk, you should be okay. (On auto models).
On manuals, I would expect the clutch switch to be used in the same way as the brake switch, to prevent the engine from revving when changing gears.

To keep things simple, I would not worry myself about adding "another inhibit switch" either at the autobox relay or handbrake.

As said before - the whole idea is to prevent cruise engaging by accident.

In a Robsey geeky way of thought - the ideal way to do this would be to isolate the inputs from the stalk switch.
And the easiest way to achieve that is to put an on/off switch in the ignition live feed between the fuse box (G2 or G5) and the cruise stalk switch (pin 4).
A standard latching switch, such as a rocker or toggle switch would do.

[maxstu]

Robsey,
You are a star, mate. Many thanks.

And guess what l did in my initial self briefing over a year ago? An additional illuminated latching switch for night time driving would be beneficial.
Unknowningly, I was ahead of myself.

If it's good enough for you to suggest then lm on it.

Regards
Stuart

[Robsey]

Here is an intriguing question...

If you got the black wire that splits off from pin 1 of the cruise control unit...

And connected this to the illumination pin of your switch...

Would it illuminate the switch to say that the cruise control is engaged.??

Just a thought?

I am making an assumption that ECU pin 1 becomes live (12volts) when cruise is engaged.
Or more accurately, when the vacuum pump is active.

[maxstu]

I don't have a latch switch to hand. Will order one soon though. Ive still to test CC in the real world. But can test later today Pin 1 and report back

[maxstu]

With ignition on and cruise control switched OFF at indicator CC arm then no power coming from module pin 1.
Switch indicator CC arm to ON and 12 volts
from ECU module pin1 all the way to pump.
The system has no ACCEL or DEC mode. So simply get to speed. Switch ON and select SET.
The VSS monitors speed and advances or retards vacuum bulb to maintain an average speed. In theory!

[Robsey]

Sounds like it is a goer then.

Excellent work dear chap!

It confirms that you could put a green tell-tale light on the dash switch or the dash itself to let you know when cruise is working.

Just like all modern cars.

The bottom left green is the planned cruise-control tell-tale on my dash - whenever it gets fitted...
Or should I say - if the van ever gets finished.

[maxstu]

Mostly thanks to you Robsey. But would the tell-tale need regulating? I did the same test with engine running and current from module Pin 1 was same as alternator charge at around 13.4v.

[maxstu]

Sorted out a few snags today.
The pinchbolt holding the homemade plate on top of the brake lever grazed the steering when rotating the offset column. Cutting 5mm from it's thread solved that one.
Before the cut....


After the cut...



I then made a test lead to check vacuum throughout the system. Connected it to pump and used a small 12 volt battery as a power source. It held the bulb in the hold position for over 30 minutes. So another tick.

Test loom....


Battery....


Bulb in hold position....


Road test coming shortly.