Webasto diesel heating with ra diators

[Diane jones]

Hi all. Back again with another question. We are now looking to install a Webasto on our boat. We cant afford a new one but  friend has recommended someone who completely reconditions them. What are your thoughts on a recon. Also I have spoken to a number of people on my Marina who complain that their heaters break down a lot. Any advice from you lovely lot goes a long way

Diane

[Alan de Enfield]

 

There are two types - marine & automotive, the cheap refurbished ones you see are generally automotive ones.

 

The voltage setting on the automotive version are higher than the marine ones as a vehicle battery is normally held at much higher voltages than a 'domestic' battery bank on a boat. When an automotive one is used on a baot it is not uncommon that the voltage in the battery is too low to fire-up the Webasto, so you need to start the engine & get the alternator to give the batteries a bit of a boost.

 

The other consideration is that the auromotive version fuel pipes and exhaust are not complaint with the BSS - and in fact the automotive ones actually emit the exhaust gases - including carbon monoxide directly into the boat. 

on a vehicle the exhaust simply allows the gases to disperse under the vehicle.

 

Just check that the 'cheap ones' you have found are suitable and BSS compliant.

Check if the seller is selling them with an automotive exhaust ( a pipe with a square box in the middle) or a marine exhaust ( a circular pipe with no square box fitted))

[Kingdom Isambard Brunel]

If you do a search on this forum you will find loads of posts about Webastos, Eberspachers, Mukinis Planars, cheap Chinese diesel heaters etc. and their faults, shortcomings and the solutions.

Its a Masterclass of diesel heating and will answer all your queries.

[blackrose]

I fitted an eBay special - reconditioned automotive unit about 3 years ago and it works really well. No issues with not working at low voltages, either because my batteries never get that low or because that's a scam to make people buy new marine units (more difficult to find reconditioned marine).

 

I found my automotive exhaust could easily be sealed with a 6mm bolt, but of course other designs of automotive exhaust may differ, so you might want to buy the marine exhaust separately.

 

If you do go for a reconditioned Webasto perhaps talk to the seller first and make sure he sends you a good one. It's a bit of a gamble but it worked for me.

[Jen-in-Wellies]

Does the use of LiFePO4 batteries change things? Their voltage tends to be higher and they hold a good voltage to a lower state of charge than Lead acid. Could you get away with automotive low voltage cutoff firmware on a boat?

[IanD]

1 minute ago, Jen-in-Wellies said:

Does the use of LiFePO4 batteries change things? Their voltage tends to be higher and they hold a good voltage to a lower state of charge than Lead acid. Could you get away with automotive low voltage cutoff firmware on a boat?

Very possibly, so long as the voltage drop in the wiring to the heater is also low enough -- which is not always the case, especially with DIY installs... 😉 

[Gybe Ho]

On 09/04/2025 at 16:37, Diane jones said:

Any advice from you lovely lot goes a long way

 

1. Focus on a fitting a generously sized cable in the power supply.
2. Don't skimp on fitting a dedicated fuel filter in the diesel pipe to the Webasto.
3. Work the heater hard for short periods i.e. don't run it like a house central heating in heating top-up chuntering mode.
4. Ensure you fit the standard Webasto diagnostic sensor socket in a convenient accessible position to simplify engineer visits for when the unit fails.
5. [Optional] Find the recent thread here where a user call @T_i_m made his own Webasto diagnostic lead. With one of these you will be able to tell a visiting engineer what the problem is before booking a visit to fix the wonky heater.

Edited April 10 by Gybe Ho

[T_i_m]

5 minutes ago, Gybe Ho said:

1. Focus on a fitting a generously sized cable in the power supply.
2. Don't skimp on fitting a dedicated fuel filter in the diesel pipe to the Webasto.
3. Work the heater hard for short periods i.e. don't run it like a house central heating in heating top-up chuntering mode.
4. Ensure you fit the standard Webasto diagnostic plug sensor plug in a convenient accessible position to simplify engineer visits for when the unit fails.
5. [Optional] Find the recent thread here where a user call @T_i_m made his own Webasto diagnostic lead. With one of these you will be able to tell a visiting engineer what the problem is before booking a visit to fix the wonky heater.

All points 100% (and yes, happy to help re diagnostics etc).

[Tigerr]

My webasto ceased working when I inadvertently ran the batteries down. Even when recharged it no longer started up. Apparently that is a thing - they have to be reset and that involves a computer, and in my case a mechanic visit. Bit of a swiz I think. Plus of course the noise like a jumbo jet. 

But when it is working it seems to do the job. 

[Kingdom Isambard Brunel]

52 minutes ago, Tigerr said:

 they have to be reset and that involves a computer, and in my case a mechanic visit. Bit of a swiz I think.

I do not think that this is true.  If the battery is serviceable and fully charged, it should fire up.  Disconnect it from the power for a while and try it next day.

[Gybe Ho]

1 hour ago, Kingdom Isambard Brunel said:

I do not think that this is true.  If the battery is serviceable and fully charged, it should fire up.  Disconnect it from the power for a while and try it next day.

 A Webasto will enter a digital sulk mode after x failed ignition cycles.

[Brian422]

17 hours ago, Tigerr said:

Plus of course the noise like a jumbo jet. 

Unsurprising as it operates like a basic jet engine 😉.

[T_i_m]

21 minutes ago, Brian422 said:

Unsurprising as it operates like a basic jet engine 😉.

I don't think most narrow-boaters suffer with heater noise as mush as the Van-life folk do because most boats are a good few tonnes of steel, rather than thin ply sounding boards.

 

You only have to see the number of threads and YT vids of people trying to reduce the dosing pump 'tick' sound!

[LadyG]

On 11/04/2025 at 16:51, Tigerr said:

My webasto ceased working when I inadvertently ran the batteries down. Even when recharged it no longer started up. Apparently that is a thing - they have to be reset and that involves a computer, and in my case a mechanic visit. Bit of a swiz I think. Plus of course the noise like a jumbo jet. 

But when it is working it seems to do the job. 

Mine made a bit more noise before I ran the diesel down and added a bottle of magic stuff, Marineset16 or somesuch, ran the Wbasto and Engine for an hour or so (to clear injectors, maybe). I think it helped.

PS I bought a bottle of Redex  Diesel system cleaner, should I try the same? I might need a few bottles as I have a larger tank than a Mini.

[blackrose]

On 10/04/2025 at 11:01, Jen-in-Wellies said:

Does the use of LiFePO4 batteries change things? Their voltage tends to be higher and they hold a good voltage to a lower state of charge than Lead acid. Could you get away with automotive low voltage cutoff firmware on a boat?

 

It hasn't made much difference to me. My automotive Webasto operates down to about 12.3v and my lead acid batteries were normally above that. Now I've got lithium batteries I don't even need to think about it because they're never likely go below 12.8v. 

[LadyG]

On 12/04/2025 at 11:14, T_i_m said:

I don't think most narrow-boaters suffer with heater noise as mush as the Van-life folk do because most boats are a good few tonnes of steel, rather than thin ply sounding boards.

 

You only have to see the number of threads and YT vids of people trying to reduce the dosing pump 'tick' sound!

Dosing pump tick sound?

Why not use gravity ?

[Alan de Enfield]

 

Would gravity produce a measured dose every few seconds, or just a free-flow ?

[blackrose]

1 hour ago, LadyG said:

Dosing pump tick sound?

Why not use gravity ?

 

Because Webastos use a fuel pump that comes with the kit. Why would you want to gravity feed a heater that isn't meant to be gravity fed?

 

It's easy enough to reduce the sound of the pump if you mount it in a rubber sling. 

[T_i_m]

1 hour ago, LadyG said:

Dosing pump tick sound?

Why not use gravity ?

I guess with a different deign of heater and a guarantee that the tank would always be above the heater then you probably could. 😉

 

Or (and people are doing this), rather than use a solenoid style pump, use a peristaltic type as they can be pretty quiet whilst still managing a controlled dose.

21 minutes ago, blackrose said:

It's easy enough to reduce the sound of the pump if you mount it in a rubber sling. 

I think most of these pumps, inc the Chinese air type come with pumps mounted in a rubber holder but the rubber is way too hard to significantly reduce the mechanical coupling and hence the noise, especially when mounted to a sounding board (the side of the case or inside a locker on a van etc). And not only does the pump itself need good mechanical isolation, so do any pipes or cables.

 

Which is a problem in say a NB engine room because everything has to be fire-resistant and so likely pipes will be rigid copper and coupling pretty firm. Luckily, bolting the pump to the structure of a 20 tonne steel boat means the std rubber mount becomes more compliant (comparatively, compared with plywood van locker or tin van floor) and so I don't think it's so much of an issue to NBers?

 

I could hear the Webasto pump running on the boat whist sitting with it in the engine bay and with the heater on  (that is much quieter than the eBay pump I bought to replace the blocked Webasto) but he couldn't.

 

Do people run the blown air heaters in NBs?

2 hours ago, Alan de Enfield said:

 

Would gravity produce a measured dose every few seconds, or just a free-flow ?

Ignoring the need for the heater fuel to be pumped (as gravity may not always be an option and can vary greatly with tank level etc) I guess a constant feed pump (pressure and rate) could be fed into a flow control valve (likely using a stepper motor these days) that should still be quieter than the std pump. 😉

[ditchcrawler]

On 12/04/2025 at 11:14, T_i_m said:

I don't think most narrow-boaters suffer with heater noise as mush as the Van-life folk do because most boats are a good few tonnes of steel, rather than thin ply sounding boards.

 

It depends if you are moored opposite one when it starts at 6am in the morning

[T_i_m]

2 hours ago, ditchcrawler said:

It depends if you are moored opposite one when it starts at 6am in the morning

Can you generally hear the (exhaust noise I presume you are referring to here, not the dosing pump, that would be a loud pump!) over the engines and do heaters not have the same run_time_limits as engines / generators?