some good info there George Anna,
for others looking on, some more tiny pieces of information on what that controller may be.
http://www.alternativasolar.com/catalog/index.php?cPath=24_29&osCsid=9c733b1a7cc4b347602898c87dc6a4ffhttp://www.casolar.net/LineaEnergiaAlternas.phpsome translation: (thanks bable fish)
In English
Controller. Measurer for systems Photovoltaic Model CMCX.12-15-20 Description: The controller of load with voltameter, model CMCX-12/15/20F provides in efficient form the protection and signaling adapted for photovoltaic systems that operate with batteries, as much for the apparatuses connected as to the batteries and the same users. In load control he in series consists of a limitor by relay towards the solar modules and another one for disconnection of the loads fed by low voltage of battery. He includes luminous indicators of normal battery, battery low and module in load, fuse, of protection when coming out and selector to inhibit the disconnection by low voltage. The expanded scale, voltameter (10 to 15 volts) this divided in colors to facilitate the user to determine the state of load of its battery (ROJO= low battery, AMARILLO= load A battery average. VERDE= battery with acceptable load). The controller - measuring it is lodged in an attractive aluminum cabinet enameled in black, in whose in front the functions above described are indicated with clarity, besides being the fuseholders, selector of disconnection for cables until caliber 10 with or without connectors. Characteristics: - Nominal Voltage 12 volts. - Current principle of solar modules: 15 amp. - Current principle to the fed loads: 20 amp. - Permissible maximum Voltage: 22 volts. - Levels of operation voltage (batteries seal with lead-acid). - Disconnection of modules (loaded battery): 14.8 + 0,2 volts. - Reconexión of modules 12,9 + -0.2volts. - Disconnection of loads by low voltage of battery: 11.8-0.2 volts. - Reconexión of loads (automatic): 13.2 + -0,2 volts. - Interrupting to select to the automatic disconnection by low voltage (normal) use of emergencia. - Fusible type 3-Ag to the loads in bayonet fuseholders. - Protection against transitory of voltage by Varistor (MOV). - Voltameter with expanded scale of 10 to 15 volts. - Precision -5% of the scale.
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this controller looks to me like.. (others, please jump in if you see different)..a shunt type controller. sometimes called a "bang bang" controller. it goes on if the voltage of our battery drops below ~12.7 to 13.1 volts and have pv power available. and turns off at ~14.6 to 15 volts...no wonder they don't like to provide the specs!
your test measurements show that the controller that gets hot was running as it should..a bit high with the voltage drop (still gonna loose a tad more before we get to the bank) the voltage output and bank readings would be good to have as well. the one we thought was running right (the cool one) was off both times you checked it. can't be sure on that one until the battery drops below ~12.7 volts. we really would have liked to see both of them running both times you checked. that is a hysterical amount of hysterics (voltage spread) built into those controllers!
also, please confirm both controllers are going to the same battery bank.
your measurements at night show us that we are NOT shorted back to the modules while off. thats GOOD!
was thinking you might get your "talkative" friend to bring out some leads off that defective fuseholder for a nice blade fuse holder external to the controller. could probably get any audio/tv shop to do that. i would stay with the 20 amp fuse. it would not hurt to put another inline fuse for each module as well rated at 12-15 amps.
i'm not here to sell you anything but you can do a LOT better than those controllers..a nice temp corrected pwm multi stage controller (just one) would put you way ahead of what you are running now, your batteries will thank you for it and there is even a chance of reclaiming those that are scheduled for retirement.
pretty good "bang for the buck" or "pop for the peso" with this one.
http://www.altestore.com/store/Charge-Controllers/Solar-Charge-Controllers/PWM-Type-Solar-Charge-Controllers/Morningstar-Charge-Controllers-PWM/Morningstar-SUNSAVER-SS20L-20A12V-Charge-Controller/p801/kind regards, dave
edit: "..it would not hurt to put another inline fuse for each.." should read ..it would not hurt to put another inline blade style fuseholder for each...those spring loaded type inline holders are trouble!
further edit: i see a terminology mistake here calling that a "shunt" type controller..more like an on/off series controller that leaves our pv circuit open when off.