I just finished a complete rebuild on a D16Z6 which included a new oem water pump ,radiator, fan, thermoswitch, temperature sensor, ect sensor and thermostat. While driving, the temp gauge is reading between the quarter to one third mark. When sitting at idle the gauge slowly climbs and the fan does not turn on. I have let it climb to the three quarter mark and no fan. I jumpered the thermoswitch and the fan turned on, so I replaced the new thermoswitch with another and still no fan. I tested the first switch in hot water and continuity was fine. I unplugged the connector from the current switch and plugged in the original switch. I put a lighter under the switch and the fan turned on which tells me there was nothing wrong with the first switch. If I let the temp gauge climb over half-way and then jumper the thermoswitch to kick on the fan, the temperature goes back down. To me this means that thermostat is open, coolant is circulating and the water pump is working. At this point I am lost as to why the fan does not come on and am looking for ideas on what else to try. Thanks.