341 / 342 - Webasto Thermo Top only starts with shore power

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Webasto Thermo Top only starts with shore power

Printed From: myHanse.com
Category: Hints & Tips
Forum Name: 341 / 342
Forum Description: 341 / 342 Hints and Tims
URL: https://www.myhanse.com/forum_posts.asp?TID=15544
Printed Date: 26 March 2026 at 21:48
Software Version: Web Wiz Forums 12.06 - https://www.webwizforums.com

Topic: Webasto Thermo Top only starts with shore power

Posted By: OnkelHugo
Subject: Webasto Thermo Top only starts with shore power
Date Posted: 09 March 2026 at 08:46

The Webasto Thermo Top heater on my 341 only starts when the boat is connected to shore power. I suspect the issue is either a dirty glow plug or a problem with the wiring.
Can anyone tell me where the heater is actually connected?
Since the cables run inside the cable duct, I can’t trace them back.

Replies:

Posted By: Arcadia
Date Posted: 09 March 2026 at 09:17

Is it possible that Hanse did not want the heater draining the batteries. Also be aware there is a low voltage cut off designed into those units.

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Leon / ARCADIA
2018 Hanse 588
Sag Harbor, NY

Posted By: Brufan
Date Posted: 09 March 2026 at 14:33

1st Consider rusty connections or cables. Hanse cabling is always on the thinner side. Just the minimum for the loads. If any oxydation occurs cable cannot do its duty anymore.
2nd If ok, check battery state of health. Maybe they are outdated/worn.

Then, 3rd check glowplug

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Bruno

hanse 355 - 57

S/Y Spicy Ginger

White hull, 2 cabins, Volvo D1-30, Selden rig, removable mainsheet track system, Simrad (now B&G)-Jefa autopilot.

Posted By: Martin&Rene
Date Posted: 09 March 2026 at 16:25

Brufan is correct. From memory, Webasto heaters need 10.5v at the heater. So check to see difference on battery and on shore power. This problem told me I needed new batteries and prompted my installing a Sterling alternator to battery regulator

If heater fails to start, I think there are error codes given by flashing lights on the control panel. (look for manual online) which can identify problem.

My heater is in back locker, so not ideal, so definitely clean connections. The other end of wiring will just be at your controller.

There is often a comment that it is not good practice to run them at a low setting for long periods as they can get a build up of muck, so give it a full power blast.

I am holiday now, back home next week when I can look at manuals and hopefully back on the yacht in the next 3 weeks to look at installation

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Martin&Rene Hanse 341 Dipper Wheel steering, 3 cabin layout, normally based in Scotland