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    Updated: 25-Apr-2006

     Back in May of 2000, Janet and I had invited some two hundred friends and family members to our home for a bon voyage party. The event was a huge affair with tents, a live band and plenty of food. The party marked our last hurrah on land - our house would be cleaned out the following day - so we emptied the refrigerator and freezer, cooking everything to prevent throwing it away. It was a real feast. Now as we motored through the Dismal Swamp Canal aboard Charbonneau two years later, I was envisioning another feast. Only this time we would be serving food to complete strangers as fast as we could cook it because Charbonneau's refrigeration system had inexplicably quit working. Unless I worked fast, all our frozen food - a full six-month's stores - would spoil.

     The day before, our cold plate refrigeration system was the cornerstone of cooling bliss. It had worked flawlessly for the previous 12,000 miles, right up until this morning when I flipped on the breaker and nothing happened. While cruising, we run the system for 90 minutes each morning to 'charge' the cold plates. The temperature inside the box then stays at an acceptable level until the following morning when we repeat the process. Now, more than 24 hours since the last run, it was a race against the clock to find and repair the problem before our food thawed.

     I should acknowledge that I was mechanically inept prior to cruising. After two years of cruising, my skills have improved markedly. In fact, I've come to thoroughly understand most systems on our boat; my education usually peaking right after they fail. This, however, would be my first lesson in refrigeration repair.

     Our Crosby refrigeration system -- a traditional ½ horsepower water-cooled, belt-driven DC motor and compressor with two holding plates -- is located underneath the galley sink and pushed as far outboard as possible. The sight glass and service valves are accessed through a cabinet door under the sink. Reaching the business end of the system, the motor and compressor, requires squeezing my 190 pound body into a 15" x 12" opening in the galley's countertop. It is a very tight fit.

     Cruising is often defined as fixing your boat in exotic locations. I disagree because it didn't seem very exotic as I hung upside down, suspended through that small opening in our galley's countertop. The view from where I precariously dangled offered no sunset views, no swaying palm trees, and no peaceful anchorages. All I saw were twists and turns of copper refrigeration tubing connected to various pieces of equipment I'd never seen before. Nigel Calder's book, Boatowner's Mechanical and Electrical Manual, helped me identify the parts. That was important so I could cuss and call each piece by name as they took turns bloodying my knuckles. Running through my mind were questions like, "Why wouldn't it run, which hidden part holds the secret to this motionless beast, and will I die upside-down, stuck in this little hole?"

     The symptoms were simple. The unit remained motionless with the breaker in the 'on' position, but there was a slight current draw showing on the electrical panel's amp meter - around 5 amps where 45 amps is normal at start-up. I also heard a faint 'thump' near the unit each time the breaker was switched from off to on. While I was troubleshooting the system, Janet called down from the helm saying, "The water pump seems to be working and the discharge water flow looks normal. Maybe the amp draw is from the water pump." I agreed and continued my inspections while she steered Charbonneau along the narrow, tree-lined canal. Adding it up, I had a lifeless motor and a faint thumping noise. Not much to go on, but at least the water pump was working.

     Experience with previous equipment failures led me to check for blown fuses or loose wiring connections first. Hoping for a simple solution, I checked the one 7½-amp fuse mounted on top of the system's wiring control box. The fuse was intact. It was time for the multi-meter.

     Progressive tests with the multi-meter showed acceptable voltages from the electrical panel to the control box and at each connection point inside the box. I continued to follow the circuit from the control box to the motor and found 13.2 volts at every test point, indicating no discernable voltage drop between the control box and the motor. All the connections looked good and showed no signs of corrosion at their terminals. So why wouldn't it run?

     Telling Janet what I'd found, she suggested I dig out the owner's manual. Like most men, reading the instructions had yet to occur to me. I was encouraged when I saw that my actions were in line with those described in the troubleshooting guide. I did, nevertheless, find one test I hadn't tried - bypassing the high pressure shutdown switch.

     The wires providing DC power for the motor are routed through a high pressure shutdown switch. This switch interrupts power to the motor if a high pressure condition exists. It could also interrupt power if the switch were faulty. I needed to test the motor by bypassing the switch. Fortunately, the switch was wired with easily disconnected male and female connectors. I disconnected the two leads and linked them together with a short piece of 12-gauge wire, effectively bypassing the switch. With the jumper wire in place, I crossed my fingers and pushed the circuit breaker to the on position - no luck. I checked for power at the makeshift jumper and found the motor was getting the full 13.2 volts. I felt I was getting closer to discovering the problem, but our food was also getting closer to thawing.

     The voltage readings were normal at every junction from the circuit breaker to the motor and the pressure switch appeared to be working; yet the motor wouldn't run. I dreaded the thought of working on the motor while being inverted and stuffed inside that small opening. Removing the motor and then working on it was a better idea, but not by much. I postponed the inevitable by investigating the 'thumping' noise first.

     It turned out that the faint thumping noise was coming from the unit's solenoids. Reading some more, I learned that the solenoids regulate power to the unit, operating like valves opening and closing depending on the box's temperature and thermostat settings. Our unit has two -- one for the refrigerator and one for the freezer. Using the multi-meter I found them to be working fine and engaging the circuit, indicating that the box temperatures were below the thermostats' minimum settings. It was another dead end.

Consulting the boating bible - Nigel Calder's Boatowner's Mechanical & Electrical Manual

     Taking a break, I surrounded myself with every how-to book on the boat and refocused my attention on the motor. What had I overlooked? Electrically, the only things left unchecked were the motor's commutator and the two brushes. The commutator is a ring of copper bars connected to the motor's armature and field windings, which turn the motor when magnetically pushed or repelled by an electric charge. The graphite brushes pass that electric charge to the system by 'brushing' against the commutator. I know that's a mouthful; I had to read three different books before I understood the process. But it was important to understand how power was applied to the motor once the wires disappeared into the motor housing.

     I decided to start with the brushes because I could remove and inspect them without removing the entire motor. The unit's two graphite brushes are reached via two access panels located on opposite sides of the motor housing. Each access panel has two screws, top and bottom, holding a cover in place. By loosening the lower screw a half turn, I found I could remove the top screw and then rotate the cover to reach the brush housing. Each brush was pressed against the commutator by a spring device, which was held in place by a locking spring holder.

     Removing the brushes, while upside down, was tedious work. I looked like a large fish with its tail hanging from a pelican's mouth - my feet kicking in the air as I tried to climb further inside. Once inside, the first spring holder was easily released by pushing it in and sliding toward one side; however, since the spring was no longer under pressure, it suddenly took flight. After spending several worrisome minutes tracking down that first errant spring, I was much more cautious with the other side.

     The next step, with both the springs and their holders removed, was to remove the wires connecting the brushes to the motor housing. Each brush has a wire molded into its body and was connected to the motor via a small screw terminal. There were two wires on this terminal; the one leading from the brush and another leading from the power input leads. The design was identical for both brushes.

     The trick was to remove each brush wire while not disturbing the power leads. It was a trial and error process, but I found that the power leads were terminated with a ring connector and the brush wires used a spade connector, open on one side. This allowed me to loosen each terminal screw a few turns and carefully slide off the brush wire, leaving the power lead attached. The brushes simply slid out of their housing after these wires were disconnected. Once both brushes were removed, I went searching for the spare refrigeration parts carried aboard for just this occasion. It also gave me a chance to let the blood drain from my head back down to the rest of my body.

     Graphite brushes are worn away over time by their constant contact with the spinning commutator. The brushes I removed looked a little worn, but it was hard to tell just how much until I compared them with the new ones. When placed side by side, it became obvious that this could be the problem. The old brushes were only a third the size of the new ones. I had learned from rebuilding previous motors that brushes should be replaced before they have worn away half their surface area. These were well past that point. Armed with new brushes I climbed back into the hole.

     Replacing the brushes was a reverse of the removal process. Each brush was inserted into the long slot that holds it in place. Being careful to not crimp the brush wire unnecessarily, I inserted the spade connector underneath the small screw terminal and tightened it. I then placed the spring in its place, perpendicular to the brush. With the spring in place, I attempted to reinsert the spring holder. It took several tries to install the spring holder. The technique required placing equal pressure on both the top and bottom of the spring while inserting the holder; tiresome but doable even while inverted with a small flashlight in my mouth. After completing both sides, I checked my work, closed the access panels, tightened the lower screws and replaced the top screws removed earlier.

     Once again I crossed my fingers and reached for the circuit breaker. I heard the 'click' of the breaker and was immediately surrounded by the sweet sound of the belt turning, the motor rumbling, and water coursing through the cooling lines. It didn't match the serene sounds of the Dismal Swamp Canal that Janet had been enjoying from the cockpit, but it sounded like a love song to me. I had solved another mechanical mystery aboard Charbonneau.

     Our refrigeration system doesn't seem as incomprehensible now that I know a condenser from a receiver from a filter/drier and can identify the other parts attached to them. The troubleshooting process was straightforward and helped me recognize which elements of the system were working and which required closer inspection.

     Don't fret the next time your marine refrigeration system refuses to work; you're probably more qualified to fix it than you think. Take your time, be methodical, and follow each possible avenue for the failure. You may ultimately need to call in a professional, but most problems are within your grasp and resolving them is a gratifying facet of cruising. This particular repair was accomplished with four simple tools: multi-meter, screwdriver, flashlight, and mirror. I imagine every boat would have those tools aboard.

     Though happy to have the problem solved, a small part of me wished I had failed. After all, not fixing the refrigeration system might have resulted in one heck of a cookout. As I put my tools away, my face was still a mixture of bright red from hanging upside down and black streaks from working with the graphite brushes. But when the sense of accomplishment settled in, I broke into a huge dimple-to-dimple smile and yelled up to Janet, "Let there be ice!"