The D2 Forums

Yes, that one that eventually fails and makes a horrible noise, so we disable it.

It doesn't seem to make any real difference other than the heater takes a bit longer to be effective in winter and the "Rest" function does very little.

BUT, I recall long ago and (to use Parliamentary language) in "Another Place" there was an intimation (maybe by MJ?) of a relatively easy solution, IIRC using A6 parts.
Is that now a long-forgotten dream or might it still happen? And for that matter does anyone care any more?

It wasn't an easy solution unfortunately , as it requires a lot of design and fabrication to fit the various bits in the D2 space. There are numerous other models which use a water-blending solution including Audis and BMWs at least, probably others. A combination of C6 / C7 pump and valves seemed possible, but alas due to the long 'vid I never managed to make a design for it. With the advent of accessible metal 3d printing it might be more feasible now though, as it needs some weird-sized very tight bends which simply don't exist to buy.

I did find that the D3 unit is materially the same as the D2, just with different pipes and wires on the exterior. I have a D3 unit in S8LOL, but sadly that only lasted a few months before the pump also died and it blows hot all the time, so the D3 unit is no more robust.

When mine decides to cook its occupants over the summer I may try and find time to redesign it...

Thanks MJ, intrigued as to why the D3 unit failing makes the HVAC blow hot though.

On both my original (PF) and current (FL) S8s just disconnecting the wiring to the pump has no major side effects.
I assume the unpowered D2 pump doesn't cause an excessive obstruction or diversion.

They all eventually fail hot, some sooner than others. The valves no longer close properly and so hot coolant is always flowing through the cores regardless of what the HVAC is set to. I've been through several valve blocks in mine to try and solve it, with varying degrees of failure. I hoped a d3 block being newer would still be working, but it made it about 6 months and did the same thing. Its sometimes ok in the summer if you start the car and immediately set it to 18c, then the valves mostly stay shut. On long summer journeys though, I will clamp off one of the heater hoses from the engine as otherwise the cabin is unbearable.

The pump assists with flow, thats about it. No pump just means it takes ages to get cabin heat - in mine, its about half an hour before its hot, and then you can't turn it off again!