Dolphin Charger Temperature Fault

[snotter]

My 5 year old Dolphin Charger has quit charging. The unit is a 12V, 60 amp model that can accommodate 3 banks and runs off of 120VAC. The problem the charger is giving me is that the LEDs indicates a battery temperature fault. To try and fix it, I bought a new thermal couple (battery temperature sensor) from defender. Defender on their web site said that the sensor was compatible with the Dolphin chargers. When I hooked it up between a battery and the charger, the same temperature fault error was indicated on the display. The battery bank is good (less than 1.5 years old) and in the heat of the summer my Sterling Pro charger says it is accepting less than ½ amp when the bank is charged and the charger is in long-time float mode. The batteries are wet cells, and, for what it’s worth, I am using 4 awg wire feeding my batteries. All wires and terminals are marine grade wire sealed with adhesive-heat shrink tubing. The wires are less than 5 years old. Moreover, the boat is used on fresh water. FWIW, the Dolphin was NOT installed in the engine room—it still looks new inside and out.
Doing a quick search of the web, I did not find any evidence of my problem shared by others. Also, I could not find where to send my charger to get repaired. Dolphin has not responded to my email.
The charger is used on rare occasions when I need to charge my batteries quickly while on the hook. I do this by using the genset to run my Dolphin in parallel with my Sterling Pro. When battery acceptance drops below 60 amps, I take the Dolphin off line, leaving just the Sterling Pro on line. The Dolphin quit working sometime during the past year when I removed it to allow me to remove my old engine and to squeeze a new engine into the boat. I was the one who bought the Dolphin and installed it in the boat. I’ve never had any issues with it before.
Please help me decide whether to get the Dolphin fixed or to buy another Sterling Pro. If anyone can recommend where to send the charger to get repaired, I would appreciate it; or, if anyone has a schematic diagram they could send me, I could fix it myself.
Thanks