EDIT--it turned out you can't swap them--they are not the same and it would fry things if you applied 120v to the 12v element----------------------UPDATE 25 Jan--12v is cooling down the freezer.UPDATE 2, 26JanI found my 120v heating element that was not working to be rusty and it and the 12v element beside it are both rusted to the coil pipe (or whatever the assembly is supposed to be like ????)I was poking with a screwdriver and it cracked open or made? a fault in the 120v heating element pipe that is rusty dark. the 12v element beside it looks identical but is shiny--maybe never used.It would be easy to swap the wiring so that the 12v element's two wires went to the terminals on the board that the 120v element's wires go to now. Only thing would be to eliminate the 20 amp fuse on one of the 12v elements wires.But--are these two elements the same so I can do that?Photo shows the 120v on the left of the 12v element which is the shiny one to the right of the photo.

Applying 120 volts to a 12 volt resistance heater may let out the magic blue smoke.

The 12v works at the moment. It pulls 9.7 DC amps according to the Trimetric. The manual says it can't do an initial cool-down, only good for keeping it cold for 4 to 6 hours --but that is battery saving advice I think.I was thinking they are the same metal part-look the same, but one just has less power on its wires when getting 12v instead of 120v. I don't use the 12v , so if it fries no loss.I can't move them so I don't know how I would replace that 120v one. I think maybe they drop into that sleeve boot thing but now are rusted in there. Not sure how it is supposed to work to change them.I could just try it and see what blows up or doesn't, but first I hope to hear from somebody who knows fridges.

When I changed my 120 v element I noticed the same thing. I had to spray the element with PB blaster and work it back and forth with a needle nose pliers because the rust was so bad. It eventually came out and I cleaned the hole out with emery cloth before installing the new one. I believe you can remove the 12v element and install the new 120 v element in its place if you can't get the old element out but can't see how a 12v one would work off 120 volts. Do you use the 12v element?

Thanks, I will see if I can shift the 12v one at all with some spray there. My question is whether the 12v element is only 12v because that is what it is being fed, or does it have a part inside it that is 12v that would fry on 120v? I doubt wire gauge is an issue here?Is it like a cigar lighter in the dashboard? Those things get red hot on 12v and ISTR are about 20 amps. This has a 20 amp DC fuse.EDIT--I broke off that 120v one where it is cracked. It is a hollow brass tube, with white hard material inside with some sort of ? threaded like a bolt--rings anyway--part down it. I guess the two wires going in the top end attach to this inside piece somehow.I can't move that 12v one even after spraying it. Can't get the bottom part of the 120v out of the sleeve/boot.I must decide whether to try the 12v on 120v (but without that 20 amp fuse) or just have 12v and gas as options. Perhaps I can do the pre-trip day's cool down on gas, switch to 12v on converter overnight, then back to gas for camping next day. (Only use the 120v for pre-trip cool down at home--always on gas for camping)

Jus tusing math to calculate wattages between the two elements, I would say they are not the same resistance.

Swap 12v for 120v Fridge Element? UPDATE 2 | Good Sam Community

BFL13
Explorer II
Jan 27, 2019
Gjac wrote:
BFL, it will come out but it takes a lot of work. Using long needle nose pliers and a pry bar tool I made to go underneath the element and a lot of PB blaster or Kroil oil it took me several hours to work the element back and forth(only about a 1/16 of an in at a time) while prying up on the bottom of the element with the bar. There is not a straight shot at the bottom so I had to bend a steel rod to the right angle to get in there.

Good to know, thanks. I am afraid to try all that in case I break the cooling (whatever it is called) pipe that goes by there, which would mean no operation on gas or electric.

I think I have solved the problem for now, so no need to risk it.
Gjac
Explorer III
Jan 27, 2019
BFL, it will come out but it takes a lot of work. Using long needle nose pliers and a pry bar tool I made to go underneath the element and a lot of PB blaster or Kroil oil it took me several hours to work the element back and forth(only about a 1/16 of an in at a time) while prying up on the bottom of the element with the bar. There is not a straight shot at the bottom so I had to bend a steel rod to the right angle to get in there.
BFL13
Explorer II
Jan 27, 2019
I like that relay idea.

This morning freezer temp is in the cold zone where it is supposed to be at -20ish C and under 0F. Fridge is also where it belongs just above freezing. (But so is ambient)

The element is on (212 watts) so can't tell if it is cycling from that spot check just now. Later observations for that.

Anyway, there it is -- the 12v initial "pull-down", which is not supposed to work according to the owner's manual.

Looking good for replacing my irreparable 120v setting with the 12v set up using the second converter with 120v input. (I cannot swap the 12v element out either --it is stuck in there despite spraying)

EDIT--it has been a few hours and no change in temperatures except fridge is now at 3C, which is below ambient. It has bottomed out for sure at the proper temps. However, I have not caught it with the element off. It is about 8C/45F out where the element is in back of the fridge, so maybe it has to stay on instead of cycle--not a clue. Was 203 watts
CapnCampn
Explorer III
Jan 27, 2019
Would it be worth it to use a relay to switch power to the element? Use the power from the board to turn the relay on utilizing the thermostat controls, then use the relay to run power direct from the converter to the element. Seem like that would bypass the voltage drop in the board, and get you the higher voltage (whatever you dial in) to the element.

CC
BFL13
Explorer II
Jan 27, 2019
So far after 10 hours on 12v, freezer temp down to -13C and fridge temp not budged--still at 6C ambient. We'll see in the morning whether this works at all. I know it usually takes a day, even on 120v. Only takes a few hours on gas though.
BFL13
Explorer II
Jan 26, 2019
Update 2

Second converter on fridge "terminal block" instead of the regular wires from the house battery bank. This was the easiest connection.

Started with converter set to 15v. 193 watts warmed up. Very slow to get the freezer to cool down any. Checked the voltage at the element pigtails 14.3v. So that is 0.7 drop across the terminal block and PC Board. About 13.5 DC amps draw (using AC watts and DC v)

Cranked the converter to 15.3 (under the 15.4 limit) and pigtails now 14.6, 202 watts warmed up. Freezer coming down in temp much better now. Acts like there is a threshold to get it really going.

Anyway, next thing is to wait for it to bottom out and cycle before declaring victory. Not there yet.

If this works I then need to find a place to mount the second converter (under the fridge has a place) and pass wires up through I hole I need to drill. Should be ok.
BFL13
Explorer II
Jan 26, 2019
pianotuna wrote:
Hi BFL13,

Be careful. My board is rated at 15.4 volts--but I don't want you letting out the magic blue smoke.

---------------

Terminology Note: This owner's manual uses "PC Board (lower)" "PC Board" and "Power Supply Module" to mean the same thing at the back of the fridge. It also uses "PC Board" to mean the eyebrow controls inside on the fridge you use to operate the fridge. I have been using "PC Board" to mean the power supply module at the back of the fridge. It gets its 12v from the "Terminal Block" at the back of the fridge where 12v wires come in from the house battery. I have voltage drop at that terminal block and also in the power supply module. I can by-pass the terminal block for when on second converter if necessary.
----------------

Same with my board at 15.4 (which was also the 5er's Norcold limit)

I need to disconnect the "fridge" 12v from house batts when powering the board from the second converter and that converter is on inverter. I have realized that puts the second converter on the house batteries, and don't want that loop. Also don't want the house batts floating at 15v.

Means an extra step going from 12v to gas, but no big deal. Have to do some wiring and rig second converter so it won't fall out onto the road. Leave the Kill-a-Watt in the mix too, so I can tell from the watts if the 12v element is on.
pianotuna
Nomad III
Jan 26, 2019
Hi BFL13,

Be careful. My board is rated at 15.4 volts--but I don't want you letting out the magic blue smoke.
BFL13
Explorer II
Jan 26, 2019
MrWizard wrote:
unless you need a new control board

at least it keeps you busy and out from being in DWs way

The control board seems to work properly on gas. I did have to replace the DC fuse on it when I fumbled something the other day.

If I get the converter to supply the board, I will have to parallel it with the regular connections from that 12v connections thing where there is some voltage drop. That way I can still run the fridge on gas when not doing any converter 12v mode. Voltage drop is not a problem in gas mode.

If I ever get this 12v mode working right, I may never use it, but at least I will have the option.

Ha--the secret is to have vital work to do in the RV so you can't get to the honey-do work just at the moment :)

EDIT-- no 120v mode means you can't run the fridge off inverter and make it up with solar to save propane. If I get this 12v mode working via second converter, I could run that converter (since not connected to house batts) on inverter and make up with solar as an option in some scenarios.
MrWizard
Moderator
Jan 26, 2019
unless you need a new control board

at least it keeps you busy and out from being in DWs way