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Starting Webasto Thermo Top Z/C


cosmin.ardelean

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Hello again.

I am having some trouble with two heaters.

I wanted to do a gift to my good friend from UK and the perfect gift for him it's a auxialiary heater. I found on internet a Webasto auxiliary heater (not W-bus or K-bus controlled) and I bought one.

The seller ensured me it can be started with +12V on Pin1. The story is complicated, in the end i received not one but 2 Webasto. When i receive the package, my worst fears came true.

One heater is BMW Thermo Top Z/C, the other one is Thermo Top C from VW. Both can be started only with the car's K-bus.

The seller does not answer to my calls anymore, so i'm on my own.

My question: what can i do to start the webasto? A new universal control unit is out of question, since the price is already high. Do you know a good priced second hand control unit?

Or do you have any advice for me?

Thank you.

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It's hard to give absolute answers to this, there's a lot of different units of these (same mechanics different software) and a lot of internet legend, some undoubtedly true, a lot of it rubbish.

As far as I've seen, a C should still be startable by grounding one pin, but not a Z.

Easiest route is to use the Webasto 1533 Oval Timer, which should start either of them. I know it has wbus output, possibly it has grounded switch output as well, but it was provided as part of the C installation kit, and will definitely start a Z in a D3, so should be a good bet.

wbus command of the heater is easy to do with a microcontroller, but obviously takes some effort if starting from zero. Mine cost sub £20 but several months of head scratching.

However, not all heaters seem to be the same, I sent one of my designs to a forum member in NZ and he couldn't ever get it to work with his Z, though it starts D3 thermotop Z with no problem, based on three units that I've tried.

I'd try using the webasto test software and a homemade interface first, to make sure the heaters actually work via wbus.

I've got a fully working aftermarket C unit that I've never managed to get the wbus test interface going.

There are a few project designs out there that will give you a headstart if you want to go that way, Try looking on the D3 owners forums?

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