propane refrigerator not getting cold

Just some general questions:
1 - -  This is model 3136 3-way correct;

2 - -  Does the Fridge get good and cold on 120VAC?
            If yes, then issue is with propane heat source.
            If no, the cooling gas "ammonia" may have leaked out.
3 - -  Has the trailer been stable and fairly level for the past 3-4- days?
            Extreme trailer left/right or tongue up/down can disrupt the ammonia distribution.
4 - -  Have you observed the Propane Flame . . . does it change size as the flame control knob is
             changed from high to low, low to high (remember to press knob in while changing flame setting.

If:
    2    =   Yes, OK on 120VAC
    3    =   No, just normal storage or driving.
    4    =   Yes, seems to be getting more propane at high setting

Then, you might try cleaning the burner assembly,  Service Manual reference: