r-mm

While I diagnose a possible servo or CCU issue I have set my driver side mixing flap to full cold, connected it in that position to its servo then removed the electrical connector to that servo. Confirmed that the passenger side servo still moves when CCU temp adjusted, driver side does not.

However I will find that while driving, I will sometimes get unwanted heat thru the driver's side dash vent. I do not know the condition of the heat dump valve - it may very well be stuck as I used to hear it make its little metallic springy-clack-slap sound when I close the driver's door but presently do not. However I thought that heat dump working or not having the mixing valve closed was supposed to result in no heat.

Any thoughts?

Pics are hard in that area but here's what I got confirming both sides are full cold (bellows compressed, actuator rods pressed toward the exterior of the car on each respective side)

JohnK964

With the flap set for CCU ull cold I’d look at the tube at your feet my passenger side had a huge hole in B it lots of heat 🥵

r-mm

I found some great diagrams J Andreas posted a while back, and now believe I understand the system better. I do believe a sticky heat dump valve can force at least some heat past the closed flapper. Mine is coming very clearly through whichever vents I have selected on the CCU so I don't think its a leaking tube so much as unwanted heat arriving at the mixing chamber via a sticking dump valve.

Does anyone know what the minimum number of removals necessary is to get at the dump valve on the left-driver side?

Peteinjp

Funny- I occasionally have unwanted heat from the passenger side..... nothing to do with the HVAC though still quite confusing and definitely related to a dump valve of some type Keeping my flapper closed has absolutely no effect- may even make things worse. Looking for a diagram online but it seems no one has been able to effectively document the system.

Rocket Rob

Peter - check the heater tubes in the footwells. If they leak, they will allow a lot of heat into the cabin. These are upstream of the HVAC flaps & servos.

https://rennlist.com/forums/964-foru...ebox-area.html
https://rennlist.com/forums/964-foru...-problems.html

Peteinjp

Thanks Rob, actually my comment was tongue in
cheek- I was referring to my better half sitting next to me in the car- and in jest.


Pete