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Dometic 3 way fridge not working on 12v?


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When you do 

Remember safety always disconnect first any AC input to your motorhome before testing

Then check with your meter the Heater for 12V DC supply as per photo attached for a 12v supply when the engine is running 

Remember 

The coupling relay and the three-way fridge relay are enabled directly by the D+ signal (or engine ignition key). The coupling relay recharges the service battery through the alternator with the engine running. The fridge relay powers the three-way fridge at 12V, with the engine running. - Both relays are excited when the ignition battery exceeds 13.4V and automatically de-excite when the engine is turned off or the battery ignition voltage is below 12.5V.

Please do not confuse with other terminal strips on other fridge models, as yours has an AC 220 V supply on the right  as per photo attached 

Regards

Fridge block connections on old fridge .png

Edited by onecal
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Well spotted One Cal ! If you looked at the other previous post terminal strip diagram , one could easily assume the three connections on the right were DC One (A) to the ground heating element DC and (B) to the plus heating DC.If the (AC)wire was live this could have been a very dangerous situation on testing for the OP.-original poster

J

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10 hours ago, onecal said:

When you do 

Remember safety always disconnect first any AC input to your motorhome before testing

Then check with your meter the Heater for 12V DC supply as per photo attached for a 12v supply when the engine is running 

Remember 

The coupling relay and the three-way fridge relay are enabled directly by the D+ signal (or engine ignition key). The coupling relay recharges the service battery through the alternator with the engine running. The fridge relay powers the three-way fridge at 12V, with the engine running. - Both relays are excited when the ignition battery exceeds 13.4V and automatically de-excite when the engine is turned off or the battery ignition voltage is below 12.5V.

Please do not confuse with other terminal strips on other fridge models, as yours has an AC 220 V supply on the right  as per photo attached 

Regards

Fridge block connections on old fridge .png

YES I agree. This reinforces what I wrote in an earlier post. Unfortunately the terminal strip in the photo is not the one shown in the Dometic manual, which is relatively inaccessible on top of the fridge.

Alan

Edited by Alanb
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Yes but this is the photo the Author sent of his fridge connector block and wiring 

Sometime the wiring may have been changed , so it's important to be able to read and understand the wiring in front of you as presented to you and never assume it's the same as diagram or indeed other similar appliances  This may help in  preventing a serious accident 

So extra care is needed 

Regards

Edited by onecal
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Hi, the multimeter came and I tested all the fuses in the box behind drivers seat. All fuses tested ok and all where getting 12.48v except the 15a 'AUX' which had about 13.6v and when engine running 14.65. I tested the red and the white wires to the fridge element before and after engine on and got about 0.05v both times. The purple I got 0.21 both times. I tested them by putting the black probe to a bolt in body then red probe to the connector block screw. (if this is wrong let me know). however, I don't think I am getting any power to the fridge. (the main engine battery was 12.89v before starting then 14.44v after. I also switched the fridge to the 12v setting.

 

Edited by antony driffill
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I would check your wiring for good connections on the block in the photo you provided 

If you look where I edited it the violet fridge supply wire does not look so good You may need to make and break

(re do the connetion)  Also Check those earths (Black/White)

The fuse box may need to be fully checked and tested for resistance (it may be corroded at the rear) 

There is a lot more that can be wrong , but check the basics first 

Regards

 

Edited by onecal
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There should be power shown if you put the + probe on the violet cable and the black probe on the white/black  terminal screw as your control has power , try using the same terminal screw when checking the red cab (engine running)

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Hi, I have checked the connector- no issues, tracing the wires, they seem to cross under the floor to under the dining seat where the water heater is, joining that wiring and then through into the fusebox behind the drivers seat. There is power to each of those fuses, but could the problem be inside that fuse box leading away to the fridge?

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 as the controls are working (apart from the 12v indicator)  the electronics must be getting a power supply which should be  via the violet cable , unless a different electronics power supply (or earth connection) has been added .

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Not sure which type of tester you have , but have you tried testing for voltage at the terminals  with the fridge  turned both on and off . It could also be worth trying a different earth point for the black probe , try the metal cabinet of the fridge.

Edited by Labby
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