First I am sorry I am confusing you...According to my books your model 300 is not a compressor operated refrigeration system, it is an ammonia absorbtion system powered by a 300 watt (aprox) 110 volt a/c (elec) heater, this heater is what begins the chemical process that turns into refrigeration... below is a snapshot of my book.<span style="font-size:10pt;line-height:100%"><div align="left">HADCO DOMETIC</div>
<div align="left">HR-2 same as RM 24</div>
<div align="left">HR-3 same as RM 36C</div>
<div align="left">HR.4 same as RM 460</div>
<div align="left">HR-6 same as RM 660</div>
HR-7 same as RM 760
</span>Yours would be the three...There are three manufactures who make the products that has the Hadco name on it in their refrigeration family line...If my book is correct you can simply replace the 110v heater with a 12v and yes it would be a 12v, if the refrigeration module were sent in to be refurbished you can ask for a 12v/propane module back intead of an electric only, (12v/110v) But you would have to beg borrow or steal the rest of the hardware you would need (pilot assembly, ignitor ect) and that would be painfully tedious...To answer honestly... this is more than you probably want to do after you factor in all the "stuff" and the different bottom chasis these units came with when gas equiped.
If your unit is compressor driven then in the back there is a round black can looking thing about the size of a grapefruit...this means your unit is made by the other two guys Hadco uses...The black can will say embrako or danfoss according to my books or a stamp "made in Italy"
Since the topic in the forum header was listed as "absorbtion system" I approached the subject from that point of view...In hindsight I should have asked the S/N and then asked the millon dollar question about if this was a compressor driven 115v or an absorbtion 115v from the start like a good technician.
I got one of these to work on from a guy who had a Serro Scotty for a member of Tin Can Tourists in Az. and he wanted to stay exactly O.E.M. so I did regardless the cost and it was converted to gas/elec...If its not important to you to keep this exact fridge
because it came with your camper then I would go the Norcold suggested earlier and your thinking much better than I am.
Even if yours is the 110v absorbtion unit and you put in the 12v heater the 12v amp draw would draw down the best deep cycle battery in about 6 hours...so the advantage of converting to 12v from 110v is minimal without gas to be the primary energy source when stoped and camping...I would not want a fridge
that makes my battery go dead that fast...You really want the 12v/Propane refrigerator.
Again for the confusion I apologize to all...
P.S. Be sure of the disposal rules for your refrigerator in your area according to its type...Freon or if its Amonia... It can very flamable, caustic and poisonous, Never puncture or incinerate this type of system, respritory distress or failure can result.
The Hadco 300 refrigerator is only 110v and does not have propane nor 12v capability. I'm confused. Are you suggesting that it could potentially be converted to operate on a battery and propane? Do you know if some of these repair companies will take an old refrigerator in (like an old car trade in) and use it's nominal worth toward the purchase of a new refrigerator? If this old Hadco cannot be made into a 3-way then I want to get rid of it and buy another unit that meets my needs. I will mostly be powering the frig. with an 85w solar panel and battery or propane. In all honesty, I don't see myself camping very often in places with full hookups. . . there are too many people and that's exactly what I am trying to escape by going to primitive campgrounds off the beaten path. Perhaps if I go camping locally at the San Mateo campground during the summer I'll use the hookups there and will need 110v. But other than that, I can't imagine myself sticking with this frig. with it's current limitations even if it does work satisfactorilly on 110v.