Webasto Thermo Top C running randomly and draining vehicle battery!

[dazcleveland]

Hey

We have a 2007 California T5 2.4TDi SE that we have owned since December 2008. Still love it to bits and although we rarely use it for camping now and it is starting to show it's age a bit, we have no intention of ever getting rid of it. Recently we have started suffering a problem with what I think is the Webasto Thermo Top C auxiliary coolant heater - I have read numerous posts on the various auxiliary heaters fitted to Cali's (WEbasto and Eberspacher!) and become slightly confused but think this is the culprit. The problem is the heater keeps running at random times, when the ignition is off, causing the vehicle battery to drain. Initially we didn't realise this and replaced the main vehicle battery thinking it was old and no longer able to hold a charge but on a recent holiday we noticed the heater was operating randomly for extended periods. I know it is supposed to operate at low outside temperatures to heat up the coolant quicker and relieve stress on the diesel engine but the outside temperature was never that cold. Eventually, after a long, stressful, search I managed to locate the relevant 25A fuse (No: 29) in the fuse box next to the gear lever and this has stopped it from draining the battery but with winter approaching and a couple of snowboarding trips to the Alps booked, I would like to try to resolve the issue.

I have taken it to a local auto electrician today who was able to retrieve some general fault codes relating to the heater but he advised that the only way to pinpoint the exact problem was for a Webasto specialist to connect their diagnostic kit and software to the unit itself. However, I am struggling to find anyone near us in Rutland and, in any case, he said that quite often it is not possible to replace individual parts on them so the entire unit may need replacing! It seems like my options are to travel a long distance to a Webasto specialist and potentially replace the entire unit at significant cost, keep putting the fuse in and out when required or remove the fuse permanently and run the vehicle without the pre-heater.

Therefore, I was wondering if any other owners have suffered the same issue and are able to offer any helpful advice / tips as to how they resolved it please?

I have attached a photo of the driver's door stickers relating to the heaters fitted to my Cali - many thanks

 

[sidepod]

All of this seems odd. My own experience of removing mine for a rebuild would suggest they’re not originally configured to run without the engine running.
I believe an additional kit was available to wire them so they could be run independently of the engine.

Essentially the input required to run without out the engine is a simple 12v supply which mimics the alternator output and the temperature sensor to allow initiation.

All that should be required in your case would be a simple switch in this power feed.
Any mechanic should be able to identify this and fit a switch.
All the wiring is available on the online easily.

Why it’s auto starting is a mystery but easily solved.

As far as spare parts are concerned, they’re very simple and easily removed and dismantled. All parts are available.

If the heater is running then clearly there is nothing wrong with it.

I also wired in a temp sensor override so I can start the heater regardless of ambient temperature.

 

[dazcleveland]

Many thanks for your response Sidepod. As you say, the bonus is the heater does actually work! The problem is it's operating when it feels like it! In the past, it has continued to operate sometimes for several minutes after a short journey, when the ignition has been turned off, but it was always when the outside temperature was low. I did ask the auto electrician whether it could be a faulty / corroded temperature sensor causing a permanent demand for operation but he said that would've been highlighted on his diagnostics check - I guess only a specialist diagnostic of the heater itself would confirm this.

Thanks for the suggestion about installing a switch - that would be much easier than having the fusebox permanently open and a pair of tweezers on hand to keep removing and replacing the 25A fuse as required!! Handy to know that spare parts are readily available too given a complete new unit looks like it coats in excess of £1000.

Thanks again for the info

 

[dazcleveland]

All of this seems odd. My own experience of removing mine for a rebuild would suggest they’re not originally configured to run without the engine running.
I believe an additional kit was available to wire them so they could be run independently of the engine.

Essentially the input required to run without out the engine is a simple 12v supply which mimics the alternator output and the temperature sensor to allow initiation.

All that should be required in your case would be a simple switch in this power feed.
Any mechanic should be able to identify this and fit a switch.
All the wiring is available on the online easily.

Why it’s auto starting is a mystery but easily solved.

As far as spare parts are concerned, they’re very simple and easily removed and dismantled. All parts are available.

If the heater is running then clearly there is nothing wrong with it.

I also wired in a temp sensor override so I can start the heater regardless of ambient temperature.

Many thanks for your response Sidepod. As you say, the bonus is the heater does actually work! The problem is it's operating when it feels like it! In the past, it has continued to operate sometimes for several minutes after a short journey, when the ignition has been turned off, but it was always when the outside temperature was low. I did ask the auto electrician whether it could be a faulty / corroded temperature sensor causing a permanent demand for operation but he said that would've been highlighted on his diagnostics check - I guess only a specialist diagnostic of the heater itself would confirm this.

Thanks for the suggestion about installing a switch - that would be much easier than having the fusebox permanently open and a pair of tweezers on hand to keep removing and replacing the 25A fuse as required!! Handy to know that spare parts are readily available too given a complete new unit looks like it coats in excess of £1000.

Thanks again for the info