| PeterFord | -- 10-14-2012 @ 8:55 AM |
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How does the temp sensor system work? Peter
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| 51f1 | -- 10-14-2012 @ 3:04 PM |
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I hope this helps: If you have a V-8, there is a thermal switch (2 terminals) in the left head (driver's side), a sending unit (1 terminal) in the right head (passenger's side) and a gauge mounted in the instrument panel. The eight requires a switch and a sender because there is no connection of the coolant in the two sides of the block (that's also why you have two water pumps and separate hoses to the radiator). If you have a six cylinder engine, there is no thermal switch, only a sending unit. The panel gauge has a bi-metallic arm connected to the pointer. It is wrapped with a heater wire. One side of this heater wire is connected thru the thermal switch and the sending unit to ground and the other side is connected to the battery through the ignition switch. With no current flowing thru the heater wire, i.e., the ignition switch in the off position, the gauge reads "hot." With maximum current flowing, i.e., the ignition switch on and the engine cold, the gauge reads "cold." With the ignition switch on, the temperature gauge reading is sent from the sending unit in the passenger's side cylinder head thru the thermal switch to the gauge. As long as the coolant temperature in the driver's side of the block remains below 200-212 degrees F (nominally 206 F), the thermal switch remains closed and has no effect on the temperature gauge reading. If the temperature of the coolant on the driver's side exceeds 200-212 F, the switch opens, interrupting the current flow, and the gauge on the panel goes to "hot." The bi-metallic arm in the sending unit also has a heater wire wrapped around it. When the arm in the sending unit is heated sufficiently by a combination of current flow through the heater and engine coolant temperature, the switch contacts in the sending unit open and close very rapidly, depending on the coolant temperature. When the contacts are open, current ceases to flow and the bi-metallic arm rapidly cools (relatively), and the contacts close again. The hotter the coolant becomes, the longer the average contact open time is and the less the average current flow to the gauge is. The heater wire wrapped around the bi-metallic arm in the gauge causes the arm to heat and deflect in proportion to the current flow. The less current flow, the higher the reading on the dash gauge (remember it reads hot when no current is flowing). Ultimately, as the engine heats (and overheats), the current flow approaches zero. When the current flow reaches zero, the gauge reads hot. I think that's pretty ingenious. Richard This message was edited by 51f1 on 11-16-12 @ 2:43 PM
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| supereal | -- 10-14-2012 @ 5:36 PM |
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The single terminal sender also contains a heating element that provides a " bias" , or reference, to the bimetal contacts. As the coolant increases in temperature, the contacts in the sender actually chatter. As the temperature goes up, the intervals increase, causing the gauge needle to reflect the change, indicating a hotter coolant.
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| 51f1 | -- 10-15-2012 @ 7:39 AM |
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I deleted this post and revised the one above to provide more explanation. Richard This message was edited by 51f1 on 11-8-12 @ 7:41 AM
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| PeterFord | -- 10-15-2012 @ 8:33 AM |
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This is the best I have seen, and it really helps. Thank you very much. Peter
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