Fridge melting fuse on 12V

[VXman]

Hello all,

Thought I'd post here as I was reading a post from 2018 which had popped up when I was researching my issue and was impressed with some knowledgeable answers with similarities to my situation.  Link to that thread below,

Anyway - my situation. I have a Burstner Lyseo on a Fiat base 2021.Owned from new. It has a Schaudt Elektroblock EBL 119. the fridge is a Thetford AES absorption fridge which only uses 12V when the engine is running.

On a trip in Europe in October I noticed the Fridge would stop working while travelling. I later noticed the 20amp fuse near the Leisure battery was melting. What became a pattern was that the fridge would be ok for a while when we set off but later in the journey the voltage of the leisure battery would dip drastically and eventually the fridge would flash and error. It was fine on Gas and 240.

I am a little confused to how the fridge is set up. I was led to understand that when on the 12V the fridge takes it's power from the starter battery/alternator. In fact  Burstner manual states that there is a 20amp fuse for the fridge next to the starter battery for the fridge. This is true and this 20 amp fuse is fine. The Burstner manual doesn't mention the 20 amp fuse next to the leisure battery or an additional 1amp one in the same place. However, this 20 amp fuse is clearly drawing a lot of current when the fridge is on the engine is on. I have asked Burstner about the purpose of these 2 fuses but they are not being very helpful.

So, really have 2 questions

1. What is the purpose of the 2 X 20 amp fuses (Starter and Leisure)

2. What could be causing the melting of the fuse and the failing of the fridge on 12V.

 

Suggestions I have had so far are a) broken 12V heating element, b) cheap fuses with poor connections, c) the fitting of a battery master drawing additional power from the leisure battery (it was wired into the fridge supply on the EBL.)

 

 

Edited November 22, 2023 by VXman

[onecal]

Hi

Check to see what amps it is drawing in operation after checking all your connections and pins (this does include the fuse pins) and all earths (especially engine earth etc') Check also main wiring for damage and check to see if the 20A fuse is rated correctly (check handbook) It may be a 25A ? Do not increase your fuse amperage until everything is fully checked by a good auto electrician.  I would personally return it to the dealer and have it corrected as you say it's a 21 vehicle . Did some come with compressor fridges? You need to check as wiring is a little different . 

Regards 

Edited November 22, 2023 by onecal

[onecal]

Hi

Just an additional note , have you actually checked your habitation is receiving power from the alternator  when as you say running ?Again I would return it to the dealer you purchased it from since it's a 21 reg 

Regards

[Derek Uzzell]

This July 2021 forum thread discussed a gas-related problem with Paul's Thetford fridge.

I don't think Paul provided feedback subsequently as to whether/how the issue was satisfactorily resolved, but I note that the dealership that supplied the Burstner was 100 miles away.  

[Alanb]

I do not have details specific to the Burstner conversion, but I do have have a Schaudt Electroblock 119 diagram, so I will start from there.

1. The diagram shows 2 off 50A fuses, which should be close to the starter and "leisure" batteries. The batteries are shown to be linked via a separate split charge relay, which is labelled "Battery cut-off relay".  It may be that the function of this relay has been replaced by a B2B.

2. The EBL 119 contains a "Refridgerator relay", and a "Fridge relay". Both relays are controlled by the D+ connection. The Refridgerator relay connects a 20A fused supply from the starter battery, which inputs at Block 2 pin 1,  to Block 1, pin 1, for an absorption (non AES) fridge.

The Fridge relay connects the above 20A fused supply to Block 1, pin 4, for either an AES, or a compressor fridge, but when the engine is not running, an alternative supply is taken from the "leisure" battery via an EBL mounted 20A fuse.

It was this 20A fuse that was reccomended for removal when an AES fridge was fitted, in order to prevent draining the "leisure" battery.

The D+ input is at Block 2, pin 2. while a starter battery negative is connected at Block 2, pin 4 and linked to Block 1, pin 3, for connection to the fridge. The converter may have taken a shortcut, and connected the fridge directly to a negative point.

Schaudt show a 2A sensor fuse for the "Leisure" battery.  This connects to Block 2, pin 5. It is possible that this has been superseded by a 1A fuse. Checking voltage on control panel with fuse removed and replaced should be a simple test.

@VXman has not made any reference to 50A fuses. I am wondering if the 20A fuse at the "leisure" battery fulfills this role?   Also how is the connection to the starter battery for charging the "leisure" battery fused (missing 50A fuse above). Should be close to the starter battery, and that applies whether or not a B2B is fitted.

As regards fridge 12V current, not easy to measure unless a clip on DC ammeter is used.  Look at the fridge rating label for Watts at 12V.  Divide watts by 12, to obtain current in Amperes (A), then multiply by 14,4/12 to compensate for alternator charging voltage. That will give the theoretical maximum current carried by any 20A fridge fuse.

Alan

[onecal]

We await the OP reply?