I called David at Annapolis Hybrid Marine the U.S. distributors for the Thoosa 9000 systems. Since the Key switch did not seem to be the issue I began thinking of other things that might easily resolve the problem. One was to disconnect the B+ of the battery to hopefully reset the controller. David said that was not necessary. I then mentioned that the power contactor relay might be bad. David ask if I had a multimeter on board. Of course I did. He suggested I remove the cover to the controller box and he could guide me on making some voltage measurements. This of course means emptying out the starboard locker and squeezing my way to large frame down below in the summer heat to access the controller box. I had not had to do this in eight years of electric propulsion operation because the system was so reliable. But, now it had to be done. I then asked a question that saved me some aggravation. In preparation of my journey down below I asked how many screws hold the cover of the controller box and are they Phillips? David replied no they are Torx (star) type screws. I did not have any Tork screwdrivers on board so I would need to buy them. But, at least I had not found this out after contorting my body down below after emptying out the locker. So it was a row back to land to get a Torx screw driver set to continue trouble shooting.
At the store I had several choices of Tork tools. The first one I picked up was a compact set that folding into the handle. It looked like it would do the trick. Though something told me that maybe I had better have a backup.
So I also bought another Torx set that had a screwdriver type handle with interchangeable bits.
Good thing I did this because I found that with the compact folding set it was difficult to access and turn the screws at the rear of the case. Where as the set with the screw driver handle was much more secure and made it easy to turn the screw. But, even then I found the controller box was just a little too close to the battery charger case to use the handle. I was however able to use just the Torx bit and a pair of small vice grips to turn the screw enough to remove it.
With the controller case finally removed I gave David another call and armed with a digital multimeter I was able to start trouble shooting. There is not much to a Thoosa 9000 system. There is of course the battery bank, motor, key switch and a box holding the controller and a few other components.
But, even inside the controller box there are many components that one finds with a diesel engine system. There is a relay, fuses, connectors. The one main different component is the motor controller. In my case it is a Navitas 400 unit. Under Davids guidance I carefully connected the multimeter ground to the B- battery connection in the box. I then checked the voltage at the power relay connections. Which was the component I thought was the next culprit after elimination the key switch. I measured 55 volts which was full battery voltage on both terminals. David explained that it looked like the the relay was good because 55 volts on both terminals means the coil of the relay is not open. What happens on turn on is after the Controller does it's self check it grounds one side of the relay which then allows full battery power to the controller. This was not happening. So it was time to look at the controller. There were two status/fault lights on one side of the controller neither one was on. David then instructed me to probe two pins on the multipin connector to the controller module. There was 55 volts across those pins. This meant the controller module was getting power. So the diagnosis is the controller is bad. David mention this had happened to other units and as a result they were no longer using the Navitas controllers because of these mysterious sudden failures. Stil I had gotten eight trouble free years out of this one and could easily replace it but, I was thinking it might be best to upgrade to the new controller David mentioned. Trouble is the new controller is larger and won't fit in to the current box. He said I also needed to check if the new slightly larger box dimensions would fit in the current space. I'm pretty sure they would but, I want to make sure and while I'm at it I want to mount it so I will be able to have enough roof to use the Torx screwdriver handle to remove the cover in the future.
So a quick ten minutes of probing and the problem was quickly diagnosed. Compared to the hours I and some diesel mechanics I had hired in the past spent scratching our heads working on the diesel it was a breeze. Unfortunately, it is getting late in the season and I would be away for several weeks. So I had a few things to think about before I decide to move ahead with a new controller box which I'll share in an upcoming post.
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