1976 Dometic Fridge Cooling Issue

Discussion in 'General RVing' started by sp, Apr 11, 2006.

  1. sp

    sp Senior Member

    So we have narrowed this issue down to the following based on SH and Boz's info: Now i need to try the most likely solution first cause i don't have alot of time. Which would you try??

    The last two trips I've had a problem with the fridge staying cold the whole time. I fire up the propane the day before we leave and it is around 40 degrees when we are ready to go (overnight). I drive to the campground(s) (3 1/2 hrs and 1/2 hr trips) and the temp goes up. I level the unit and let it sit and the temp still is high (~4hrs). I switch to electric, which never seems to cool properly from day one about 3 years ago now, and it gets cool but not enough (over night). I switch back to propane and in a few hours it is at 40 again. There isn't a complete pattern of when it does this.

    (This is for non electronic controlled refers). Sounds like it could be your themostat has gone bad. To check the t-stat you need an extra person. you take the t-stat metal tube out from under its hole @ the fins in the refer and put it in some icewater. The heighth of the flame should change. if it doesn't change it out.

    To check the "Heating Element", first (as Kirk suggested) unplug the AC cord. Remove the two wires from the control board leading to the heating element. Set your meter to OHMs, at it's lowest setting, (Rx1 for analog meters). Attach your leads to the wire ends and note your OHM reading.

    Or, You might also have your LP pressure checked, This requires a special guage called a "monameter". Any shop can do this, and it only takes a few minutes. A high LP pressure creates to much heat, and can cause the cooling unit to crystalize, blocking the plumbing.
     
  2. Kirk

    Kirk Senior Member

    1976 Dometic Fridge Cooling Issue

    Steve,

    I really hate to say this as it isn't good news, but to me it sounds like the cooling unit is loosing its refrigerant, or it is plugging up. Either one would require a new cooling unit. Since it does cool, just not enough, it is very unlikely that the problem is either propane or electric. The propane supplies more heat to make the system work so it should work best. If it is low on ammonia/water mix or partially plugged up, or both, then you would get cooling but it would be very sensitive to leveling and it would not be able to keep up when temperatures get warm. It might help to supply extra ventilation by putting a fan in the opening at the base to blow more air across the coils. In the long term I suspect that your 30 year old refrigerator is reaching the end of it's life.
     
  3. sp

    sp Senior Member

    1976 Dometic Fridge Cooling Issue

    Kirk,

    My friend owns a heating and cooling business and he is bringing over his monometer to test one of the two items listed. Then we will try the ice water trick to check the thermostat.

    If i was a betting man my money would be on the thermostat being messed up or shot. I'm a little thick headed so I'll try everything I can before giving up. :blackeye:

    sp
     
  4. ARCHER

    ARCHER Senior Member

    1976 Dometic Fridge Cooling Issue

    I believe most of these RV type fridges have a useful life of approx 8-10 years if used on a regular basis. If left to sit for months at a time, it is not good for them, as things kinda get hard inside the pipes due to sitting. I just replaced one last Dec, due to cooling unit going bad, and it was not much more to get a new fridge in lieu of replacing cooling unit.
     
  5. Kirk

    Kirk Senior Member

    1976 Dometic Fridge Cooling Issue

    "I'll try everything I can before giving up."

    That just makes good sense, as long as you balance what you spend to repair the present unit aginst the age of the refrigerator and the fact that it might fail again next month.
     
  6. sp

    sp Senior Member

    1976 Dometic Fridge Cooling Issue

    Kirk, I here you loud and clear on that one. Archer, what did you pay for the new one?

    thanks,
    sp
     
  7. ARCHER

    ARCHER Senior Member

    1976 Dometic Fridge Cooling Issue

    SP,
    It wasn't cheap. With labor to remove the old one, cut the inside hole and little wider and install it the total costs was around $1,495.00. I went from a three way to a two way also, so saved a little there and it did just fine while traveling down the road using LP. I had always been somewhat afraid to use LP while driving. I turned it off each time I stopped for gas and all worked fine and the fridge stayed a lot cooler than the old DC current from the old 3 way. Next time (if there is one), I'll buy and install myself to save about $300.00 labor. ;)
     
  8. sp

    sp Senior Member

    1976 Dometic Fridge Cooling Issue

    Thanks Archer. I knew they were up there but did know they were that high.

    Here's the latest. My friend is comming over to go thru it with me tommorrow afternoon so I figured I'd get it going to see how it acted.

    7am fired it up on cooling #4
    5pm took therm that read 67 f,room temp, and placed it in fridge.
    5:10pm checked, 54 f
    7:30pm 32 F then put it in freezer
    7:45pm freezer 18 f put it back in fridge
    10:50pm fridge 29 f and turned it down to cooling # 3

    Will check it in the morning.

    sp
     
  9. sp

    sp Senior Member

    1976 Dometic Fridge Cooling Issue

    The latest:

    The pressure ranged from 11" to 11.7" as we cycled the thermostat up and back.

    The flame rose and fell as we cycled the thermostat up and back.

    The temp settled out as 35f after adjusting the therm down to a lower settting.
     
  10. Kirk

    Kirk Senior Member

    1976 Dometic Fridge Cooling Issue

    SP

    That sounds to me as though it is working properly? Perhaps it got well? If it were me I would keep it operating for a few days and keep a close eye on the temperature. If it continues to work, I don't think I would spend any money, just keep and eye on it. With a refrigerator that age, watching it is always a good idea. We keep a small thermometer inside of ours all of the time, even when new. It is mounted on the door where we see it almost every time we open it. Just a good practice to know what is happening and you do have to increase the setting when in really hot weather. That is quite normal.

    It might be that something had blocked, or partially blocked one of the cooling tubes and that it has cleared now. If it keeps working, just use it!
     
  11. Kirk

    Kirk Senior Member

    1976 Dometic Fridge Cooling Issue

    OOPS
     
  12. s.harrington

    s.harrington Senior Member

    1976 Dometic Fridge Cooling Issue

    The refer should be 36deg F and freezer should be 10 deg F. It is usually best to run your refer set on #3. Sometimes if the t-stat is bad it will still work right between 0 and 1.
     
  13. ARCHER

    ARCHER Senior Member

    1976 Dometic Fridge Cooling Issue

    Temp also depends on what you have loaded in it and the air circulation. I find when I have a lot of stuff in the fridge, the temp runs between 38-40 degrees, but several degrees lower if I have less stuff in the lower part of the fridge. Also, don't forget to defrost once in a while. The temp will go up pretty quickly when the door is open, so don't be surprised if it gets over 40 right after you open it or right after Momma puts leftover (warm) stew, etc., in it.
     
  14. benwd

    benwd New Member

    1976 Dometic Fridge Cooling Issue

    I have heard that if the fridg is removed and placed upside down for a few days that blockages in the cooling system can be cleared. I've never done this or seen it down so it's not personal experience.
     

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