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Old 07-07-2003, 12:46 PM
Arthur Dalton Arthur Dalton is offline
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,768
You are getting correct info..
The aux fan for a/c is simply a saftey circuit to aide the High Side pressure from getting out of wack under High Thermal Load by cooling off the condensor with air-flow... [ this reduces the high side pressure]..
This circuit uses a dropping resistor ans is LOW fan... if you are seeing HIGH fan in this circuit , someone may have jumpered the resistor [ guys in the South do this to give a little more flow to condenser demand]
In Hot climates , it is common to see the fan come on fairly consistently, but in cooler climates, there is no DEMAND for condensor air-flow aid as there is no high side burden due to lower Ambient temp...

In cooler climates , one will usually see the fan cycle when at idle coming off a run [ ie. at a stop light ]. This is a good indicator of proper operation in mild climate[ I actually use a high idle , hood closed , 2-3 min test for this condition].
Remember , the high side pressures change at different thermal load conditions, and the aux fan is there to keep the high side in check when called for ... it's main puorpose is to keep the high side from getting so high that the sw will cut off the compressor
due to un-checked high side pressure other words -it works in that window of pressure conditions....
On the ECT resistance thing, the ect sensor is actually a NEG
thermistor --ie- the resistance gets LOWER as the temp increases... and that lowering trips the fan module control...
Some fool with this sensor for a lower trip point, but others have had better luck with a lower thermostat... [ my preference]
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