12v woes on Dometic fridge

[hiram6]

I've pulled my Dometic fridge and have it sitting on a workbench cleaning and refurbishing it. Since I've owned the Westy, it has always only worked on AC, never on propane or 12V.

I hooked up a 12v source to it and began checking for voltage at various points along the wiring, found one or two questionable connections and cleaned them up. After cleaning up the wiring, I now get heat from the 12V heating element. It warms up enough that I can feel the tube getting hot where it exits the top of the insulated stack, but it never gets hot enough to heat up the fins

Left it hooked up to a battery for 24 hours, battery was hooked up to a battery charger. 24 hours later, it still had heated no further, and, more importantly, the interior of the fridge was still the same as room temperature.

I'll move on to troubleshooting propane later, but would like to have the 12V function working. I've looked at all the threads in the stickies, I've done a search. I've printed off and followed Frank Condelli's fridge how-to, but I'm not finding anything on how to troubleshoot 12V beyond just confirming that voltage is getting to the right place.

Any help? Do I just need a new heating element?
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1985 Westy, 1.9L automatic (Daisy)
1996 Mazda Miata
1998 Jeep Grand Cherokee 5.9 Limited

You can't lie around on the beach and drink rum all day.................unless you start first thing in the morning.

[crazyvwvanman]

There are 4 white wires coming out of the heat box, 2 for 12 volts and 2 for 110v. Make sure you have the right 2 for testing with 12 volts. Connect them to a charged battery and measure the current amps the 12 volt heater is drawing. Should be about 8 amps.

The 12 volt wiring before the actual heater wires tends to get cooked over the years because people leave the fridge set for 12 volts and drive it that way for years and years without realizing it. By directly connecting to the 2 white wires you can determine if the heater itself is at fault. The 12 volt heater is a separate part that can be replaced easily enough with the fridge out.

You need to hook BOTH wires up to the battery. You can't rely on anything else for the ground side, only the actual heater 12v wires. Use a 20 amp fuse for safety sake during testing.

Mark

[1621]

Perhaps my 12v function is toast, but I've never had success in cooling the interior of the fridge on 12v alone. I've always used it simply to maintain temperature while underway until I get to a spot to use either 120v or propane.

Slightly off topic but 12v Dometic related and something you may consider while the fridge is out:

If you have an auxiliary battery and have lost the ability to automatically cut 12v power to the Dometic when the engine is off, consider adding a relay to the wiring in order to prevent accidentally draining your aux. battery. I did this after frying my last battery forgetting to turn off the 12v feature.

The relay sits atop the fridge, and the wiring only took a few minutes to complete.
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'85 Westy

[hiram6]

I did the direct to 12V test for the element while I had it removed from the stack. It got HOT!!

What I should have done was tested how hot it got once I reconnected to the fridge wiring, maybe it doesn't get AS hot once it's getting current through the various connections and switches on the fridge.

I'll throw the multimeter on my bench test set-up and see if it's drawing the 8 amps. Haven't done that yet.

Good call on setting up the relay, I eliminated the factory relay set-up when I changed to a Yandina set-up for my aux battery.

When I say the interior of the fridge didn't get cold, let me clarify, the aluminum fins inside the fridge are room temp according to my IR thermometer.
_________________
1985 Westy, 1.9L automatic (Daisy)
1996 Mazda Miata
1998 Jeep Grand Cherokee 5.9 Limited

You can't lie around on the beach and drink rum all day.................unless you start first thing in the morning.

[crazyvwvanman]

The fridge can get COLD running on only 12 volts. Mine makes ice on the fins after many hours of driving. The trick is to correct all the poor connections along the way and run it from a well connected power source. If the heater element gets low voltage you should expect low performance. I eventually ran 2 test leads out from the terminal block where the 2 white wires screw down. This let me measure the voltage across the heater element while running the engine. I also put an led on the stove front that glows when the fridge element has 12 volts on it, hooked to the 2 test wires. Then I can see at any time when the fridge element is drawing 12 volts. Mine sees more like 13.5 volts when engine is running and works great.

Mark

[Vanagon Nut]

I recently wired up my Dometic to 12V. It gets cold no problem.

There is a set screw that holds the element into the small tube. Is it present?

That element needs to be up against the metal to transfer heat properly. Pic shows 182A (12V/AC elements in one package) but gives you an idea.

I eliminated the fridge relay (I like living on the wild side ) Doesn't seem to make any difference to fridge performance on 12V.


Neil.

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1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[hiram6]

Neil, I do have the screw to tighten it down, and it does seem like the tube the element slides into is nice and snug up against the larger tube. And of course on mine I have a separate tube for the AC heater, which works fine.

When I connected the element directly to a 12V battery, it got DAMN HOT very fast. When I reinstalled it into the tube, and connected it through the fridge wiring, it seems like I lost something, I need to get home tonight and check for the 8 amps draw, and also check each connection in sequence to see if I'm losing juice somewhere. If the heating element isn't getting a strong 12V I would imagine it would still heat, just not to the best of it's abilities. Might be what's happening to mine.

Chasing electrons and grounds. The mantra of a Vanagon owner!

[Vanagon Nut]

hiram6

Do you have the Dometic service manual?

The fridge wiring diagram is likely on the fridge itself, but the manual has that and more.

Powered disconnected, double check that all the wires at the wire block on fridge are screwed down.

Are all the wires in the right place on wire block?

Is the fridge switch on panel connected properly?
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN