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Thermostat operation

Yahoo Message Number: 71017
From some of the questions being posed, it appears as though some may not understand what a thermostat does. The thermostat , let's say one that is 180 deg, has the purpose of keeping the engine at that minimum, operating temperature. At 175 the thermostat is closed and keeping the antifreeze/water solution circulating within the engine. At 180 it starts to open and let the radiator dissipates the excess engine heat. Typically the thermostat is fully open at 10 degrees warmer than 180(at 190 in this case ). After 190, the fan is modulated to keep the engine at the proper temp. On my ISX that operating temperature trying to be maintained by the sensor/computer is 195 degrees. The point that seems to be missed , by some, is that if you are running at a higher temperature, say 195, the thermostat is fully open, and no longer plays a part in the temperature control. The thermostat must be in place, as it's resistance to flow of water /glycol is part of the pump head , and if you remove it , you can flow much more water than required. Once you turn the A/C on, you need to have airflow over the condenser coil, which is in front of the engine radiator. The fan controller -Sauer-Danfoss takes over ( as the a/c condenser needs airflow but the engine may not ) , because at that point, the engine could be cooled, too much, by the radiator . The radiator may actually cool the water/ glycol enough that the thermostat comes into play to keep the engine warm enough. I have simplified as much as possible, but that is roughly how the system works. It gets reasonably complicated as the Danfoss takes info from the engine and a/c to optimize control. Hope this helps.

Ron Baran 09 Magna 7025