12v Fridge Element

[Craig]

I'm no qualified electrician but I can read . Unless things have changed since they printed this service manual (Granted the manual is from the states), and I sincerely apologise if they have, but you'll have to take that up with Dometic PeterQ.

This is a copy from Dometic AES Refrigerator Diagnostic service manual

for any A.E.S. to operate
on any heat source the refrigerator must
receive a 12 volt supply to the positive and
negative connections on the terminal block at
all times. The refrigerator must be connected
directly to the house battery with 2 wires of
adequate capacity to avoid a voltage dr

I think the big clue is that you are only getting 8 volts at the terminal block. The following is from the same manual.

As with the first and second generation series
A.E.S. models, any time the battery voltage to
the terminal block drops to approximately 9.5
volts DC, the refrigerator will switch to a
nonthermostatically regulated gas flame to
insure the unit will still provide cooling for
the customer. As a low battery indication, the
green mode switch indicator lamp will shut
completely off during the voltage drop.

[oldtrack123]

Hi Craig
I do not know were you got that manual from but as you say it is USA ,they may do things different

BUT All the Dometic AUS manuals ,including AES,I have seen , CLEARLY state
The Fridge HEATER heater should be supplied from the vehicle battery with heavy cables via an isolator .

The AES models manuals state exactly as Chris has
THREE DC feeds
[1]from the vehicle to the 12V heater circuit
[2]A PERMANENT feed from the VAN 12V battery to the Control input terminals
[3] A signal feed from the vehicle /Alternator D+ to the FRIDGE D+
There are several good sound electrical reasons for it to be done that way
And the D+ signal plays a BIG part, one of it's function is to isolate the fridge 12V heater from the vehicle battery when the engine is not running
An reason is the heavy fridge load does not affect the HOUSE battery SOC
Reduced voltage drop in the house battery charge circuit even if it has a DCto DC charger
So perhaps YOU should take it up with Dometic ,if YOURS does not follow the recommended method for AUS model fridges

PeterQ [a qualified electrician]

[Craig]

Thanks PeterQ

[Dot]

fridge.jpeg

fridge2.jpeg

fridge3.jpeg

Do what the manufacturer says and here it is in B&W

[SteveW]

I appreciate all of the interest and help.

I feel sure I am going to be able to establish that the element is short circuited. I will pursue the issue of why the apparent heavy draw on the vehicle 12v cable did not blow the fuse or pop the circuit breaker - which ever it is when I find it.

I'll post the results when I find out.

Regards

[oldtrack123]

Hi Dot
Thanks for the Pics
They confirm my points
PeterQ
[Retired but still qualified electrician]

[Craig]

Thanks once again PeterQ

[SteveW]

The verdict is in - Guilty.

The manufacturer of the motorhome is responsible.

The power cable from the vehicle battery to the fridge begins with a 60 amp fuse at the battery end - a good thing.
The 12v heater element draws 24 amps - a heavy load.
There is another fuse box at the rear of the vehicle cabin where the 12v cable from the fridge meets the 12v cable from the vehicle battery ( the point where the Fiat wiring meets the Jayco wiring). This has (had) a 20A fuse - a bad thing.
The 20A fuse has melted in the fuse holder but not blown, however, the melting process has created a resistance across the fuse pins which, apparently explains why the voltage at the fridge end of that cable was showing 8v.

Pictur of the fuse attached.

Open for discussion.

[BruceS]

Good find!
Let's hope it wasn't helped by a fault in the fridge?
Put one of these in instead Steve.
http://www.ebay.com.au/itm/40-AMP-Manua ... 27cff07ae2
I couldn't find one in Australia like it but I got mine from an Auto Pro shop.
Saves a heap of fuses if you're trying to fault find!!! Just press the end button!

[SteveW]

It has a 35A fuse in there at the moment. A 25A went in first and quickly became hot to touch.

I intend to raise the matter with Jayco before I make any more permanent arrangement. There would be liability issues if I made a change and a fire occurred. Mind you, it's lucky that a fire didn't occur. It is a bad mistake to use a fuse that has a lower capacity than the load and I can only assume that other vehicles have the same problem. The relevant fuse box clearly identifies the fuse as being for the fridge and as being 20A. My guess is that the set up is as it was for earlier models of the same motorhome that had a single door fridge with a 175w element, whereas the 2 door fridge in the latest model has a 275w element - big difference.

Seems to me to be something that should be the subject of a recall because all others the same as mine could be at a risk of fire.

The Dometic installation manual calls for a 30A fuse. You can see that on the copy of the manual that Dot posted. (above). I would like to be assured that the Jayco installed fuse holder is rated for 30A.