RV Pro Article September 2007

In the August issue of RV PRO, we ended with the cooling unit being exposed and ready for servicing. Let's move on to preparing the cooling unit for reconditioning.

Releasing Pressure

At this point it should be noted that customized tools are needed to discharge and charge the cooling units. All other tools needed are common hand tools.

If the boiler pack and refrigerator fins have not been removed from the cooling unit, remove them at this time. Of note, be sure to wear eye protection for the following steps.

If you are not sure if the unit still has a charge, take the cooling unit to a no-traffic, well-ventilated area and invert the cooling unit. To do this, follow --..,

these steps:

Slightly loosen the service stem. (At this point you will need the Ford RV customized tools).
Connect the customized Ford charging wrench to the service valve on the cooling unit.
- The site glass in the Ford Formula Board (FFB) must be empty.
- The vent and discharge valves on the FFB must be open.
- Empty the charge, if any, into the FFB.
If there was not enough pressure in the cooling unit to force the liquid into the site glass, close the service valve, remove the Ford charging wrench, and proceed to next step.

Deurethaning

If a leak is suspected, check for signs while deurethaning. Pressure washing the entire cooling unit is necessary because it removes the urethane, loose paint, dirt, and rust from the unit. Urethane is removed by using a pressure washer with a high-pressure stream of water.
Typically. 1,700 pounds is adequate, but we recommend using one that deli vets 3,100 pounds of pressure or greater. The greater the pressure, the cleaner the unit, and the less time involved. Using a "0" tip provides a fine stream of water. This works best for cutting off the urethane. Rotate the unit in all positions to assure 100 percent urethane removal. When completed, allow cooling unit to dry.

Phase One: leak Check
Of note, eye protection should be worn for this procedure. Follow these steps:
- Attach the discharge line from the Ford leak check manifold to the Ford charging wrench. Now attach the charging wrench to the cooling unit and pressurize the cooling unit.
  - Check for leaks using Fords W.A.P. leak check formula.
  - If no obvious leaks are present, increase nitrogen pressure.
  - Check for obvious leaks by repeating the above steps until leak is found or you have reached the maximum pressure, as instructed in the training.
  - If no leak appears, skip to Phase Two leak checking.
    
    Phase Two: leak Check
    Of note, again, eye protection should be worn for this procedure.
    Follow these steps:
    - With the nitrogen still in the cooling unit, bagatize the unit.
    - Leave the unit overnight.
      - The next morning, check for ammonia odor or yellow discoloration.
      - If a leak is detected, mark the leak and discharge the nitrogen pressure before moving to the next step.
      - Repair the cooling unit by welding the leaking area (as demonstrated in the picture on page 50).
      While some in the industry are recommending replacing the entire evaporator! boiler in the cooling unit, we do not practice this procedure. We believe that it's not necessary, that it's an extra expense and that it involves extra time.