12 volt frig question.

Yeh, I'm asking in reference to our new 2019 camper frig. Why I was asking is, I was trying to figure out if the current was constant (assuming a constant voltage) or variable. From the responses it seems that a "normal" t'stat controls the 12V heater element and it is either on or off. One response indicated that some older frig's were direct wired without a t'stat and the heater element ran as long as the selector knob was set to 12V.

I thought there may be another way were the 1-10 knob set some constant voltage to the heater element, say setting 1 = 6 volts and setting 10 = 12 volts, but that does not seem to be an option.

So the bottom line is that the 12V heater element cycles on and off via a t'stat in a similar way as the 120V heater element cycles on and off.

thanks all!
bradw

NRALIFR wrote:
He’s got a new F-350 and 1062 Lance, Doug. Due to the forum issues, he probably hasn’t been able to update his signature.

I've been meaning to update my sig for a while. But now I just tried and get an error message. I'm logged in via RV.net. Anyone know how I can change it?

thanks,
Brad

NRALIFR wrote:
He’s got a new F-350 and 1062 Lance, Doug. Due to the forum issues, he probably hasn’t been able to update his signature. I haven’t either (darn it).

What about a 2001 vintage Dometc RM3663? Is the DC element direct or tstat controlled? If it’s direct, that would explain some behavior that led me to conclude that the tstat set points must be different vs. AC mode. Thx.

:):)

DC mode on your Dometc RM3663 has to be manually selected....IF selected to operate in DC Mode then Temp Set point controls the operation of the DC Element

In Auto Mode...DC has to be turned OFF otherwise it will operate on DC Mode only
Auto.....AC has priority then swaps to GAS if AC is unavailable
Will swap from Gas back to AC when AC power is restored
***Provided DC Mode is OFF

Short answer is yes. the control computer controls all 3 power sources 12/120 and Propane (Assuming it's an RV type absorpton fridge)

now some of the 12 volt "Coolers" may not have a T-Stat (these are what I call -70 boxes.. Room temp - 70 degrees is about the best they can do and some only -40)

And last but not least they now make a line of 12/120 volt like my engel. Thermostat controlled.

But the answer to your question based on what I can infer from your question is YES there is a thermostat. Or as JRR Tolking would say "one Ring To Rule Them All" (Ring = Thermostat).

Hi NR,

Try a different portal. The goodsam one does NOT allow changes to be made--but I know that one of the others does.

NRALIFR wrote:
Due to the forum issues, he probably hasn’t been able to update his signature. I haven’t either (darn it).

:):)

BFL13 wrote:
The 12v heating element on our 1991 Servel Dometic S630 fridge gets the temperature down and then holds it there, so it must be cycling to hold it there. I have not watched it long enough to see it go on and off.

The following info is just additional for my weird set-up:

The 120v element drew 350w at start-up but that quickly fell to lower 300s when it got hot. It has since rusted out and no longer works, so I use the 12v to cool down the day before a trip. Once hot, it draws 202 watts from the adjustable voltage converter I have running the 12v element according to the Kill-A-Watt. So less wattage than the 120v element, but enough to do the job.

I have to set the voltage at 15.2 volts (staying under the 15.4v limit of the fridge control) to get that 202w because of voltage drop on the 12v wires. If I set it at 13.5 I only get in the 100s for watts and it does not cool down enough. There is a big voltage drop in the skinny fridge wires to the control board, the board itself, and some in the wires to the element, not just from the OEM battery to fridge wiring I don't use for 12v mode.

Next morning before leaving, I change out the 12v wiring to the fridge from the converter to the OEM 12v wires and go on propane. ( I have an extra converter for this, which is mounted under the fridge in the "furnace room".)

It takes about eight hours or so to get the fridge down to proper zone temps from ambient, so overnight on the 12v works great.

I could run the fridge this way instead of propane if getting enough solar, but haven't done that. Propane is on from leaving home to getting back from going off-grid.

Your model does go thru the tstat. Doug

The 12v heating element on our 1991 Servel Dometic S630 fridge gets the temperature down and then holds it there, so it must be cycling to hold it there. I have not watched it long enough to see it go on and off.

The following info is just additional for my weird set-up:

The 120v element drew 350w at start-up but that quickly fell to lower 300s when it got hot. It has since rusted out and no longer works, so I use the 12v to cool down the day before a trip. Once hot, it draws 202 watts from the adjustable voltage converter I have running the 12v element according to the Kill-A-Watt. So less wattage than the 120v element, but enough to do the job.

I have to set the voltage at 15.2 volts (staying under the 15.4v limit of the fridge control) to get that 202w because of voltage drop on the 12v wires. If I set it at 13.5 I only get in the 100s for watts and it does not cool down enough. There is a big voltage drop in the skinny fridge wires to the control board, the board itself, and some in the wires to the element, not just from the OEM battery to fridge wiring I don't use for 12v mode.

Next morning before leaving, I change out the 12v wiring to the fridge from the converter to the OEM 12v wires and go on propane. ( I have an extra converter for this, which is mounted under the fridge in the "furnace room".)

It takes about eight hours or so to get the fridge down to proper zone temps from ambient, so overnight on the 12v works great.

I could run the fridge this way instead of propane if getting enough solar, but haven't done that. Propane is on from leaving home to getting back from going off-grid.

The electronic controls do switch the 12 volt element through a 30:amp relay.

He’s got a new F-350 and 1062 Lance, Doug. Due to the forum issues, he probably hasn’t been able to update his signature. I haven’t either (darn it).

What about a 2001 vintage Dometc RM3663? Is the DC element direct or tstat controlled? If it’s direct, that would explain some behavior that led me to conclude that the tstat set points must be different vs. AC mode. Thx.

:):)

If you still have the 1996 Lance, odds are the 12 volt element is DIRECT, without a Tstat. Back then, the 12 volt element was direct wired thru the selector switch. The 12 volt element on direct wired refers is ONLY for cooling when the Truck engine is on and you are in Transit. The 12 volt element keeps the existing cold in the refer and is not designed to cool the refer down. Doug