Retrofit Telestart T90 on T5GP ThermoTopC: recognized, but does not start

[Peterb84]

I have added a T90 telestart to my T5.1 (2011) with Climatronic to enable warm starts in winter . However it does not actually start the ThermoTopC coolant heater...

What did I do:
I bought a used T90, and connected it according to VW drawings:
pin1 to +12V
pin2 (W-bus) to T6au/1 of heater,
pin 6 to GND.

I also had to code the heater module to 001031 (was 000031). And magic happens! In VCDS I can see that it is recognized! See screenshots (only German version has the label files for my heater): Status Funkfernbedienung changes with dis/connecting the T90 on the power supply (pin1).
I had found on another forum: https://www.vwvortex.com/.../starting-aux.../post-113961419 , that one does not need the keyfobs (which are a bit expensive...), but the telestart can also be started with pin3 en pin4:
pin 3 = output for heater start (also shown on this forum in the large auxiliary heater upgrade topic)
pin 4 = input for heater start

This indeed seems to work: upon applying +12V on pin4, half a second later I get +12V on pin3 (checked with LED). I also see traffic on the W-bus: voltage drops from a constant +12V to 0V for a very short period (seen on scope).

Problem:
Unfortunately, the heater does not start.. The heater is working fine otherwise, for example by starting using VCDS: Module 18 - Basic settings - CH1 - button ON. There are no fault codes, diesel tank filled just above the red, battery voltage is 12.8 - 14V (on charger).
I do not see a reaction in the measurement blocks upon applying voltage to pin4 neither. Everythings stays off.

Question:
Any clue why the heater does not start then? Or how could I further diagnose this (with VCDS, scope, but without Webasto diagnositics)?
Every help is much appreciated.

 

[oldiebut goodie]

As far as I know ThermotopC does not use W-Bus. It operates purely on 12v signal. The T90 should be able to give this .
All my Telestarts are in the workshop and am just going out so can't double check which wire from Telestart but easy enough to find with a meter. ( Pin 3 I think )

 

[Peterb84]

As far as I know ThermotopC does not use W-Bus.

That would be very surprising.. In fact, I tried that first, and did not work. I then found that VW branded ThermoTop use special (VW specific) W-bus, and therefore bought a VW telestart to connect to the famous pin1 (at heater). As such is also documented in the VW ErWin flow diagrams.
The T90 module is recognized, as written aboven, and I get the confirmation signal out of pin3 (at T90) as well. Just no heat. ;-)

 

[oldiebut goodie]

Still found no mention of W-bus for T5 installation of Telestart in the VW T5 documentation for Thermotop C. (The Telestart that was fitted to these was the T60 not the T90.)
What controller are you using at present to start the heater? That should tell me whether you have W-bus start or not.

 

[Peterb84]

Interesting, thanks for looking. I actually have no controller; I start with VCDS (basic settings), and it starts upon engine start in the cold. No timer or such.

I found a T5 manual on TTC retrofit, with T91, for up to 2012: https://www.butlertechnik.com/downloads/VW_T5_2004+Amarok_2012_D_Climatronic_installation_manual.pdf

In there it looks like simply connecting as I have described in my first post.

However, I also found a T5 manual on TTC retrofits, with T91, for 2012 or later: https://www.vwt4forum.co.uk/attachments/1321086a_vw_t5_tdi_2012_aufrustung-_insel-pdf.208586/
Although my van is 2011.. With CAAC engine. Supposedly T90 and T91 are interchangable, so I assume the diagram is valid for my hardware.

Apparently there is an additional relay needed that enables StA which is connector MV. I just do not know what that is.. Apparently needed though for telestart? Or not on my 2011 van

 

[oldiebut goodie]

In that manual both of the connections are shown as using 12v not W-bus. The 1533 timer shows the green/white being connected to the 12v output and so does the Telestart connection. ( W-bus connections are usually on a yellow wire ) I don't speak German so am going on how it is shown only.

 

[oldiebut goodie]

Following on:

StA and MV are the vehicle coolant pump and fan ( I think )

Looking at the wiring diagram again - everything is triggered by 12v not W-bus as I said originally. green/white carries the 12v signal either from VWU ( the 1533 timer ) or T91 ( the Telestart ) to start the vehicle's pump etc. via relays K1 and K2. The W-bus is used to fire up the heater but the vehicle side must be put into operation first with the 12v signals. That is how I see it in that wiring diagram. I presume that the heater will not fire up as the operating conditions on the vehicle side isn't being met.
(It all appears to be signal cables after the relays also.)
I only work on the air heaters so these old water heaters are a learning curve for me.

 

[Peterb84]

Alright, I found some more documentation that I had downloaded before. Specifically for ThermoTopC and VW T5 and T91 telestart. You should not add relays or such, and the signal (from R149 = telestart to J162 = ThermoTopC) is W-bus according to VW themselves:



Also attached are installation manuals for the T91 to the ThermoTopC on a Climatronic T5 and T6. Both show simply connecting them on the X1/pin1 and T91/2, without adding relays.
So I am pretty sure now my wiring is OK and complete.

Perhaps it is something simple but non-trivial like an error on the HVAC module (I removed the rear control temporarily), or not having set the Climatronic to max heat or something..

 

[Scottish Scrutineer]

Problem:
Unfortunately, the heater does not start.. The heater is working fine otherwise, for example by starting using VCDS: Module 18 - Basic settings - CH1 - button ON. There are no fault codes, diesel tank filled just above the red, battery voltage is 12.8 - 14V (on charger).
I do not see a reaction in the measurement blocks upon applying voltage to pin4 neither. Everythings stays off.

IIRC, does the fuel tank not need to be above 1/4 tank for the fuel burning heater to operate?

 

[oldiebut goodie]

The relays should already be present I would have thought, not something that you have to add. The diagram in post 5 shows them on the vehicle side.

As above.
Fuel level may well have a bearing on a non-start on coolant heaters, as I said I work on the air heaters.

Ideally you need to be using Webasto Thermotest rather than VCDS then you may gain an idea as to what is happening. You can then see if the Telestart is talking to the heater.

Of course your T90 might not be giving the correct W-bus command for your heater as your heater was operated by the T60 originally. They are not all the same - I have a box full that will not start certain heaters as they send the wrong commands.

 

[Peterb84]

More diving into the Parking heater upgrade (1321086a_vw_t5_tdi_2012_aufrustung-_insel-pdf.208586), I found that the MV is a solenoid, which is added (in the parking heater upgrade) to the water circuit to prevent the warm-up of the engine, and the heat only goes to the cabin heat exchangers:

Upgrade VW T5 Comfort Kit – Island Circulation
To increase the heat input after upgrading the supplementary heater to a parking heater, we developed an island circuit.
With an island circuit the upgraded heater VW T5 with Climatronic behaves like a serial heater.
NOTE: For island circuit, the motor will NOT be preheated
Part No.: 1321085A
G1-Price: 126,05 Euro

However, I actually want to warm up the engine, so I do not need the solenoid bypass. This solenoid is furthermore completely stand-alone, so it cannot prevent starting of the TTC by a remote T90/T91 start signal.

So back to the issue at hand, I indeed believe I will never find out without Webasto diagnostics, which I am not willing to spend on this.
Perhaps the VW information of the diesel tank fill should not be in the red is incorrect, and it should be above a certain value. Just as well it could be various other conditions not met.. Or the wrong signal being sent by T90 and I should have had a T91 or T100HTM instead (although I doubt it, as VCDS says 'recognized').. Or something else..

 

[Scottish Scrutineer]

I am increasingly certain that the fuel burning heater needs to know that there is more than 1/4 tank of fuel to enable it to run. Usually the feed pipe from the tank doesn't go to the bottom, so to avoid it drawing air, it is disabled below a certain fuel level. If there are repeated failures to run, it will lock out, so I'd suggest adding more diesel before you try it again.

 

[Peterb84]

I am increasingly certain that the fuel burning heater needs to know that there is more than 1/4 tank of fuel to enable it to run.

Will try that first. I would have expected that it would not start from VCDS - Basic settings - ON then as well. Although that started even with diesel in the red, so perhaps the VCDS "expert" start bypasses some conditions.

 

[oldiebut goodie]

If you connect to the heater with Thermotest via W-bus you can then test whether the heater can be turned on with W-bus signal alone bypassing everything else.

 

[Alied]

Stupid question but does the coolant heater on a T5.1 need to be flashed with different firmware like on the T6 in order to work as a parking heater?

 

[Peterb84]

Stupid question but does the coolant heater on a T5.1 need to be flashed with different firmware like on the T6 in order to work as a parking heater?

Guess not, that is a ThermoTop Evo, not ThermoTop C. And T6 uses T91 LIN telestart, which is totally different from (w-bus) T90/T91.

 

[eugene]

@Peterb84 did you manage to sort the Telestart?
I don't know if it's been said before - the pin on the webasto side is different for T6 and T5. For T6 it's pin 2 and for T5 it's Pin 1.

 

[Peterb84]

@Peterb84 did you manage to sort the Telestart?
I don't know if it's been said before - the pin on the webasto side is different for T6 and T5. For T6 it's pin 2 and for T5 it's Pin 1.

Not yet. I think it might be fuel level related, or another electronic check.
On my T5.1 it is pin 1, and the signal is not the issue, as the communication is working shown by the VCDS status information.

 

[TomSab]

I have same problem do you solved this?
I try buy webasto ECU 7E0815071A and 7E0815071C and no possible start heater via remote...in kufatec site is possible remote install upgrade heater!
I have T5.1 2014 try coding engine,webasto,climatronic and no possible start webasto via remote...

 

[TomSab]

Try 4 units Telstart and thermo test run webasto with wbus I understand what block webasto