Rear HVAC not heating - Shuttle / Caravelle / California

[Adi-66]

Pic for attention

Anyone had an issue with a T6 (17my) shuttle / caravelle / California rear HVAC unit working exactly as prescribed, chilling nicely moving air to the requested zones - all buttons on front and rear panel work and the unit responds, the 2 solenoids on the rear hvac move on command- BUT the water pipes to the unit don’t get warm so no direct heat in the rear! (45min drive this evening, coolant stable at 90’c, with zero increase in temperature of the pipes to the touch - I removed the rear 1/4 panel to gain access)

I’m thinking there must be a front rear thermostat/ diverter / splitter valve to send hot water to the rear when sufficient temp is reached?
Anyone have any suggestions to aid a fix without a dealer visit please?

Any ideas?

 

[Adi-66]

Bump

 

[n10n]

There are quite many variants depending on engine code, whether auxiliary water heater is installed, DSG vs manual etc.

Some models have a Y-piece with a thermostat (2) controlling the heat distribution with main heat exchanger (1) and additional (=rear) heat exchanger




In some other models the additional heat exchanger (2) is simply parallel to the main heat exchanger (1)




And still in other models the heat exchangers are parallel but supplementary heating (2), ie Webasto auxiliary water heater, and the associated circulation pump (4) can affect the flows:




Note that I used 132kW engine pics here simply because they were the most clearly drawn.

If the rear pipes don't warm up at all I would maybe guess your system is like the first picture and there's an issue with the thermostat in Y-piece, wherever that may be located. Alternatively I suppose the rear heat exchanger might be blocked somehow and then it doesn't really matter which type of a setup it is.

 

[Adi-66]

Hi Guys,
Sorry to Hi-Jack this thread.

I have a Shuttle (LWB and Chestnut brown, just like the OP) that also has the sticker in the door for the Webasto (ZZ9 option code - Thermo Top Evo - Part No: 5Q0.010.014.D)

Getting heat out the the cab heater is fine and takes about the usual time you'd expect for a cars engine to get hot on a cold day... it's certainly not a super fast heat delivery as I would expect with having a Aux heater fitted.

Questions:

1. I've got no idea if the thing is working or not!
2. Upon switching off the engine on a cold morning I can hear a faint Buzzing / Wizzing kind of noise coming from the area where the heater should be, this last for about a minute post engine off, then stops.
3. Is their anything I can do to check it's functionality?
4. Can it be updated via S/W H/W to make it into a Night Heater?
5. Anyone know of a Midlands based expert on all things heating in a T6 shuttle?

And on another Heater note...

The rear HVAC in my shuttle also isn't getting hot - I've stripped out the rear 1/2 panel and partially stripped the rear HVAC unit and their is water in the pipes at the rear condenser / radiator unit, all of the arms are Ok, and the lower flap moves on command from the overhead console, (but only a very small amount), moving it manually makes no difference to heat output or pipes warming etc
The coolant never gets warm no matter how long I drive for?

Question:

1. Is their a secondary thermostat that will bring in the rear HVAC circuit once the front / engine is sufficiently warm? maybe that has failed?
2. Anyone know of a Midlands based expert on all things heating in a T6 shuttle?

TAGGING IN @Robert & @mmi as from other threads you guys seem to be the experts

 

[Adi-66]

There are quite many variants depending on engine code, whether auxiliary water heater is installed, DSG vs manual etc.

Some models have a Y-piece with a thermostat (2) controlling the heat distribution with main heat exchanger (1) and additional (=rear) heat exchanger

View attachment 270000


In some other models the additional heat exchanger (2) is simply parallel to the main heat exchanger (1)

View attachment 270001


And still in other models the heat exchangers are parallel but supplementary heating (2), ie Webasto auxiliary water heater, and the associated circulation pump (4) can affect the flows:

View attachment 270002


Note that I used 132kW engine pics here simply because they were the most clearly drawn.

If the rear pipes don't warm up at all I would maybe guess your system is like the first picture and there's an issue with the thermostat in Y-piece, wherever that may be located. Alternatively I suppose the rear heat exchanger might be blocked somehow and then it doesn't really matter which type of a setup it is.

Thank @n10n I suspect its the thermostat Y Piece - i have no idea where it is physically located on the car though and I can't find any resources that show me either a coolant layout against the physical location on a vehicle.

 

[mmi]

TAGGING IN @Robert & @mmi as from other threads you guys seem to be the experts

Ahhh... it seems that editing the post doesn't trigger messaging to tagged members, anyways... @Robert

Webasto (ZZ9 option code

Are you sure about the code Z99 - it's not recognised in wiring diagram.
Would be helpful to have the heater option code from the build sheet.

Is their anything I can do to check it's functionality?

Fault codes readout would be the first step.

Can it be updated via S/W H/W to make it into a Night Heater?

Well, basically yes. However, it's 5kW is probably too much and not very efficient as it warms also the engine thus better suited as a "parking heater".

OEM Webasto Auxiliary Heater To Parking Heater Upgrade

All required components are already purchased, tested and ready for the installation. Well invested €58=£49 :thumbsup: My ODIS-E is also ready to upload new(better) firmware ;)

www.t6forum.com

Webasto Auxiliary Heater - customizing

On my 2017 T6, I have a Webasto auxiliary/water heater and Eberspacher air/parking heater fitted at factory. The remote and timer only controls the Eberspacher air/parking heater. The Webasto aux/water heater only kicks in whilst the engine is running and the outside temp is 5 degrees or below...

www.t6forum.com

Webasto Auxiliary Heater - customizing

In my panel there is only two symbols: either ventilation (blower only as in the linked picture) or cabin heating (heater symbol). The engine heating is not indicated any way in the panel. Does this make sense? Perhaps you could post a picture of your manual and symbols of the control panel...

www.t6forum.com

Is their a secondary thermostat that will bring in the rear HVAC circuit once the front / engine is sufficiently warm? maybe that has failed?

Some have, some don't. A build sheet is needed to know what's the exact configuration.

 

[n10n]

Are you sure about the code Z99 - it's not recognised in wiring diagram.

My build sheet has both Z99 and ZZ9 - looks like ZZ9 is the intended one here

 

[n10n]

Thank @n10n I suspect its the thermostat Y Piece

Is their a secondary thermostat that will bring in the rear HVAC circuit once the front / engine is sufficiently warm? maybe that has failed?

Some have, some don't. A build sheet is needed to know what's the exact configuration.

Having looked at some more diagrams it seems to me the Y-piece thermostat for additional heat exchanger is only used when auxiliary heater is not installed - and it kind of makes sense as the aux heater can provide ample water heating, there would not be much reason to limit rear circulation. Happy to be corrected though if this is wrong.

 

[mmi]

the Y-piece thermostat for additional heat exchanger is only used when auxiliary heater is not installed

The 20 above joins the into piping to rear heater - 1 below

 

[n10n]

The 20 above joins the into piping to rear heater - 1 below

Yes, additional (rear) heat exchanger may well be installed although the auxiliary heater (webasto) is not, and in those cases there's the Y-piece. For example "1.1.7 Coolant hose schematic diagram, vehicles with manual gearbox and 2nd heat exchanger" from CXEB workshop manual, items 8 & 9:

 

[mmi]

Again the 20 joins the into piping to rear heater

 

[n10n]

View attachment 274703
Again the 20 joins the into piping to rear heater

View attachment 274702

Well, happy to be proved wrong

This looks much more accurate than the workshop manual diagrams, they depicted auxiliary heater systems without the Y-piece.

 

[mmi]

Well, happy to be proved wrong

This is much more accurate than the workshop manual diagrams - those depicted diagrams having auxiliary heater without the Y-piece.

Well, not sure about being right or wrong - just put out a couple of diagrams where the thermostat was. I simply lost track about the PR-codes (it's already midnight for me).
It's just amazing how throroughly things actually have been thought - and documented.

 

[n10n]

It's just amazing how throroughly things actually have been thought - and documented.

Agreed. I suppose dealers can simply get exact correct diagrams by VIN, slightly trickier for us outsiders to parse the configurations based on PR codes, engine type and manufacturing year

 

[Adi-66]

Hi @n10n & @mmi Thank you so much for the replies.

It looks like maybe the elusive Y piece Thermostat (#9 on this image) is located near my Webasto aux coolant heater (which is under the LHS (passenger) seat area) .... I'l get the shields off and see if I can find it to replace and try to fix my rear heat issues.

 

[n10n]

It looks like maybe the elusive Y piece Thermostat (#9 on this image) is located near my Webasto aux coolant heater (which is under the LHS (passenger) seat area) .... I'l get the shields off and see if I can find it to replace and try to fix my rear heat issues.

Good luck with the search!

It sounds like the most probable cause. And apparently the illustration pretty much looks like what it should look in the real world as well:




I also tried to search my underneath photos for a match, unfortunately hadn't captured that exactly. But this is looking from from behind the gearbox towards left front wheel. I would start my search from somewhere those 3 galvanised pipes go up in behind of heat shield or maybe towards up and right in picture where the starter is.