Dometic fridge voltage polarity question

[VanTalk00]

I cut my Dometic DC cord to hard wire it to my 12v bus.  I thought I was being careful, but now I'm wondering if switched the wires and got the polarity wrong.  The attached photo shows the voltage I have at the fridge plug.  When I plug it in, I get no DC power to the fridge.  It works fine on AC.  I'm hoping I didn't damage the fridge if this polarity is wrong.  If it is wrong, I guess we know what happens when you give it the wrong polarity.

Can someone who has this same Dometic cord plug confirm the voltage I'm seeing in the picture?  Do I have the plus and minus wires reversed?  I submitted the question to Dometic, but it's been a while, and they haven't responded.

Thanks!!!

Jim

 

[B and C]

Normally, on 12V wires from the factory, one of the two wires has a white strip or writing on it. This is the positive wire.

 

[user 423]

Look at the wires going into the plug. Does one have a raised 'rib' on it?

If so, that one is the positive wire.

The rib will run down the whole length of the wire.

Edit: Or a white marking or writing as B and C says.

 

[MrNoodly]

Yes, ribbed to positive.

If you have ribbed going to positive, then maybe what you have it attached to is wired incorrectly.

 

[VanTalk00]

Yup, the left side is ribbed and hence should be positive.  I've got it reversed.  I'll reverse it in the morning and let you know if it behaves.

Thanks!

 

[tx2sturgis]

On the Dometic cord that you show in your picture (identical to mine) the smooth wire is the positive. 

I'm looking right at mine, tested it. Confirmed.

Ribbed is NEGATIVE.

If you hold the connector up, cord exiting at 6'oclock, socket facing you, index notch downward, the metal pin receptacle on your RIGHT is the positive pin when the cord is wired correctly at the other end.

At least, that is the way MINE is wired.

 

[B and C]

Must of been someone new making the cords that day TX. White lines, writing and ribs has always been the electrical standard for positive.

At least you identified the positive pin. A meter will make short work of getting it correct.

 

[user 423]

I'm looking right at mine, tested it. Confirmed.

Ribbed is NEGATIVE.

Even though my Alpicool is a different manufacturer, the plug looks identical to the one in post #1.

Same thing as TX2. The wire to the right contact is unribbed and is the + positive wire.

But then it does have writing on it.

 

[VanTalk00]

On the Dometic cord that you show in your picture (identical to mine) the smooth wire is the positive. 

I'm looking right at mine, tested it. Confirmed.

Ok, so now I'm not sure what to do.  Guess I need to speak with someone at Dometic.  If I swap it to test, do I do further damage?

Recall the original problem is that when I press the power button, nothing happens though I clearly have voltage all the way to the fridge using the polarity I showed in the pic.


Jim

 

[user 423]

Does it use a 'brick' (AC to DC power adapter) to operate on AC?

Or is there a separate AC cord/plug that goes directly to the unit?

 

[maki2]

When trying to get help with appliances if possible please give the model number of the fridge. When someone does that then persons such as myself can do the background research bringing up manuals, wiring diagrams, trouble shooting trees and also videos. But there are so many Dometic brand models that have been produced over the years that it is not possible to get you very specific information about your exact refrigerator without knowing the model number.

For instance if knew the model number I could potentially find you a copy of the service repair manual such as this one that was posted on the internet. The link I am posting is unlikely to be the fridge you yourself have but you can take a look at it and see the type of information that would be of value to your for figuring out your electrical issue on your own. So please, try to find the model number and I will take the time to see if I can find the service manual for your specific fridge. It will be a great document to have on hand for this issue and any other issues that might come up over the years.
https://fourwheelcampers.com/NewDometicRefrigeratorManual.pdf

 

[tx2sturgis]

This is a portable 12v compressor fridge, judging by the picture, probably a CF_30 to 40 size....just guessing.

Not a built-in absorption fridge.

Rarely are service manuals available for these chinese-made portable coolers.

 

[tx2sturgis]

Recall the original problem is that when I press the power button, nothing happens though I clearly have voltage all the way to the fridge using the polarity I showed in the pic.

Basic trouble-shooting 101: "Replace with known good"

Did it work on 12v before you cut the cigarette lighter plug? (assumption vs actual test)

Possibly there is an internal 12v fuse in the cooler? Dunno...not gonna open mine to find out.

If you have the time, you might purchase another factory cord (locally or online) or borrow one locally if you know someone nearby with a similar unit.

This would help you verify operation on 12v and the connector polarity.

 

[maki2]

This is a portable 12v compressor fridge, judging by the picture, probably a CF_30 to 40 size....just guessing.

Not a built-in absorption fridge.

Rarely are service manuals available for these chinese-made portable coolers.

I had one for a while I was going to use but sold it because I found an Engel which was a better fit size wise.  It ran fine on 12v but when they new owner tried plugging it into his vehicle it did not run. The issue was not with the fridge, the issue was the cigarette lighter plug in his car vehicle was worn out. Plus of course the manual does say the wiring should be coming directly from the battery and of the correct gauge wire for the distance.   They are very  sensitive and won't run if the battery is too low because they have an internal sensor that shuts the fridge off to keep from draining a battery too low.   So the issue might not even be the wiring and plug on the fridge. It could be the wiring from the battery or it might be the battery itself.  That makes several things to troubleshoot.

 

[tx2sturgis]

Contrary to opinions expressed here and elsewhere, there is no 100% universal 'standard' to adhere to when it comes to wiring with tracers, ribs, markings or lettering. All manufacturers and individuals are on their own when adopting whatever standard they wish to use that day, that year, or for an entire lifetime.

Probably more than 75% of the time, you will find the positive wire or hot wire as the one with the tracers, the ribs, or the lettering, but this is not the same thing as a 'standard'.

I'm not referring to different colors, like red and black, or white and black, that DO denote polarity.

Tracers, ribs, and lettering are simply there to define which conductor is which, at each end, during manufacture or modification. Unless it's a red tracer on a black wire...things like that DO usually denote polarity.

But it is always best to test. Make SURE you know what the polarity is before assuming.

 

[VanTalk00]

Contrary to opinions expressed here and elsewhere, there is no 100% universal 'standard' to adhere to when it comes to wiring with tracers, ribs, markings or lettering. 

This is a Model CFX65DZ  Dometic fridge.

I have solved the polarity problem.   I found the original cig lighter plug that I cut.  See the attached photo of a continuity test between the outer prongs (not the center stab) and the ribbed conductor.  This confirms that the rib corresponds to negative polarity, and my original connection was correct.

HOWEVER, this doesn't solve my original problem, which is that when I press the on button on DC, nothing happens.  It works fine on AC, and I've had it working on DC before, but before I reconfigured the connecting cord and thought I had messed up the polarity.

I'm not confident that Dometic will respond.  Anybody know who services Dometic in Vegas?  I'm not opposed to diving in to trouble shoot, but I don't have the wiring diagrams, disassembly notes, etc.  If anyone has opened up their Dometic, let me know.

Thanks,

Jim

 

[VanTalk00]

I had one for a while I was going to use but sold it because I found an Engel which was a better fit size wise.  It ran fine on 12v but when they new owner tried plugging it into his vehicle it did not run. The issue was not with the fridge, the issue was the cigarette lighter plug in his car vehicle was worn out. Plus of course the manual does say the wiring should be coming directly from the battery and of the correct gauge wire for the distance.   They are very  sensitive and won't run if the battery is too low because they have an internal sensor that shuts the fridge off to keep from draining a battery too low.   So the issue might not even be the wiring and plug on the fridge. It could be the wiring from the battery or it might be the battery itself.  That makes several things to troubleshoot.

This is an interesting possibility.  Maybe the longer cord created too large a voltage drop.  But it isn't really that long, and it seems like SOMETHING should happen when I press the on button.  See the post above about the polarity problem.  Think I solved that one.

Jim

 

[user 423]

How much longer is it and did you use a larger gauge?

 

[VanTalk00]

How much longer is it and did you use a larger gauge?

The original configuration was #12 from the battery for about 5 feet to the other side of the van, then spliced into the original cord, shortened to about 2 feet to the fridge.  This configuration worked fine.  Then I decided I wanted to swivel the fridge out from time to time and lengthened the shortened original cord to about two more feet, using the same original cord.  So the final config was #12 for five feet, then 2 feet of original cord, then two more feet of original cord.  Perhaps the extra splice caused the problem?

I suppose I could replace the original cord with #12, yielding, #12 for 5 feet, splice, #12 for four feet, splice, then the plug.

 

[highdesertranger]

I am assuming you checked the plug and hand both positive and negative? wiggle test? highdesertranger