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Old 04-23-2017, 12:18 AM   #1
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Dometic 12v wiring question

Checked the wiring on my 3 way Dometic fridge, 12v is all wired up correctly except for the 12vD+ which is the sensor wire which goes to the alternator, this is not connected so never used the 12v to run the fridge. When I did connect it to a 12v power supply from house batteries the fridge switched over automatically when the AES button was pressed but only lasted 10 seconds and fuse blew, changed the 15amp fuse same thing 10 seconds and blew again, any ideas please.
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Old 04-23-2017, 07:30 AM   #2
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Post the model # of your fridge, it will help members give you feedback.....
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Old 04-23-2017, 02:51 PM   #3
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Quote:
Originally Posted by fonzie View Post
Post the model # of your fridge, it will help members give you feedback.....
Here we go, model is Dometic RM4605. 186 litre
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Old 04-23-2017, 04:43 PM   #4
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OK I will take a try at this. This fridge is 12vdc/240vac/LPG. The 12vD+ when connected to vehicle trailer plug, is sensing if the tow vehicle is running and if it is, then switches to DC automatically. Since you are just hooking up your lead to your trailer battery, maybe it draws the voltage down lower than 12 volts and fuse burns to prevent killing battery. Hook up a 12 volt charger to your battery, have a multimeter and monitor voltage drop, if voltage stays above 12 volt and fuse does not blow after a period of time then that would be your issue....it needs to be hook up to your towed vehicle though the trailer connector....hope it helps......



From the manual:

12V OPERATION
AES will select the 12V mode of operation as soon as the
vehicle engine is running (detected by the alternator connection
of the fridge D+).
If the 12V DC goes down below 9V DC, the system will shut
down completely

http://www.dometicrvcentre.com.au/do...nager/item/117
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Old 04-24-2017, 06:50 AM   #5
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Just another note, when you do this test make sure the trailer is not connected to shore power, otherwise the AES will try to go between shore power supply and DC power supply...I think?
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Old 04-24-2017, 08:24 PM   #6
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Quote:
Originally Posted by fonzie View Post
OK I will take a try at this. This fridge is 12vdc/240vac/LPG. The 12vD+ when connected to vehicle trailer plug, is sensing if the tow vehicle is running and if it is, then switches to DC automatically. Since you are just hooking up your lead to your trailer battery, maybe it draws the voltage down lower than 12 volts and fuse burns to prevent killing battery. Hook up a 12 volt charger to your battery, have a multimeter and monitor voltage drop, if voltage stays above 12 volt and fuse does not blow after a period of time then that would be your issue....it needs to be hook up to your towed vehicle though the trailer connector....hope it helps......



From the manual:

12V OPERATION
AES will select the 12V mode of operation as soon as the
vehicle engine is running (detected by the alternator connection
of the fridge D+).
If the 12V DC goes down below 9V DC, the system will shut
down completely

http://www.dometicrvcentre.com.au/do...nager/item/117
Thanks for the replay fonzie, just had one more go at diagnosing the problem, change the fuse again( 3rd fuse in 2 days) and this time had only blown it once doing it this way and no more blown fuses,what i did was wire the 12vD+ wire direct to the house(trailer) battery and not to the 12v main feed wire into the fridge, the 12v side of the fridge has never been used and the 12vD+ has never been connected to any 12v source untill now(only ever used LPG or land power) i checked the voltage at the wire coming out of relay to the fridge it was 13.2v as the solar panels were charging the house batteries, when i switched the fridge on to AES( no land power connected) the voltage went down to 11.6v and stayed around there, when i checked the voltage at the house batteries it was 12.6v with the fridge still on, does sound right to you,
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Old 04-25-2017, 04:33 AM   #7
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watts to amps at 12v question

Quote:
Originally Posted by savi18 View Post
Checked the wiring on my 3 way Dometic fridge, 12v is all wired up correctly except for the 12vD+ which is the sensor wire which goes to the alternator, this is not connected so never used the 12v to run the fridge. When I did connect it to a 12v power supply from house batteries the fridge switched over automatically when the AES button was pressed but only lasted 10 seconds and fuse blew, changed the 15amp fuse same thing 10 seconds and blew again, any ideas please.
Just checked the data on my RM4605 Dometic fridge and at 12v the input is 275 watts to the heater element, now at 275 watts at 12v the amps are 22.9amps that is using watts to amps calculator, the fuse fitted is only 15 amp should this be higher say 20 amp fuse to accommodate the higher amperage,

Ps:The fridge has behaved it self today as per my post above.
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Old 04-25-2017, 05:24 AM   #8
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For the voltage difference between battery at 12.6 and 11.6 at refrigerator would be normal as there is voltage lost in the wiring between the two. In the attached manual it does say the the fridge has a 30 amp fuse supplying the heater. So it seems that you have it working properly........also according to the wiring diagram, you should have a 3 amp fuse for control board and 30 amp fuse for 12 volt dc heater and no 15 amp fuse is shown....


connection marked “Connect to Vehicle 12 Volt DC Battery”

This connection supplies the 12 V DC heating element.
The (+12V) and (-) poles have to be connected directly to the
vehicle battery. (Via a suitable connection to the tow vehicle
when fitted to a caravan.)
Do not use the chassis for the return lead.
This 12 volt DC vehicle battery terminal is supplied and fitted
with a 30 amp fuse situated at the rear of the refrigerator.
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Old 04-25-2017, 11:33 AM   #9
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If your rig is a trailer, then you shouldn't use the 12V cooling option for the fridge which is why the wire wasn't connected. The current load to run the 12V heating element is much more than can be provided from the tow vehicle's charge line to the trailer. If your rig is a motorhome, the 12V fridge heater would be effectively drawing directly from the alternator when the motor was running and it would work without problems.

If you want to cool the fridge on 12V and it's a towable, you could do it by running a #8 or #6 wire from the alternator back to the rig for the fridge 12V heater circuit. You might also have to install a heavier ground wire between the two vehicles.

Phil
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Old 05-18-2017, 05:03 AM   #10
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Quote:
Originally Posted by fonzie View Post
For the voltage difference between battery at 12.6 and 11.6 at refrigerator would be normal as there is voltage lost in the wiring between the two. In the attached manual it does say the the fridge has a 30 amp fuse supplying the heater. So it seems that you have it working properly........also according to the wiring diagram, you should have a 3 amp fuse for control board and 30 amp fuse for 12 volt dc heater and no 15 amp fuse is shown....


connection marked “Connect to Vehicle 12 Volt DC Battery”

This connection supplies the 12 V DC heating element.
The (+12V) and (-) poles have to be connected directly to the
vehicle battery. (Via a suitable connection to the tow vehicle
when fitted to a caravan.)
Do not use the chassis for the return lead.
This 12 volt DC vehicle battery terminal is supplied and fitted
with a 30 amp fuse situated at the rear of the refrigerator.
Still blowing fuses(15 amp) checked over the electrics today and wiring to to fridge goes through a 50 amp small relay, when i disconnect the 12+ from the relay to the fridge heater element the fuse does not blow even with a 5 amp fuse fitted, so this means no problems from the relay back through the fridge circuit/board, what i think is happening is the electrician who wired up the fridge(and i think done here in NZ) has run the fridge 12+ from the house battery through the fuse panel(with a 15 amp fuse) then to the relay, not realising the fridge draws 275 watts at 12v which is approx 22 amps so to many amps for the 15 amp fuse, there is a white Dometic fuse box near the fridge and i think is fitted with a 30amp and 3 amp fuse to protect the fridge main board, why the electrician fitted a further relay i dont know, when i do fit a 20 amp fuse it does not blow and the small 50amp relay gets only slightly warm also the 12+ wiring from the relay which is only around 1 foot long to the fridge heater element gets very very slighly warm which is i think normal considering its running approx 275 watts(22 amps through it).
Your views please,
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Old 05-20-2017, 03:33 PM   #11
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