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<blockquote data-quote="SNAKEYE" data-source="post: 15951259" data-attributes="member: 22534"><p>There is a switched ground wire mod to manually switch the fan on as long as the switch is left in the on position. A certain wire coming from/going to the ECU is tapped into and run to a switch conveniently mounted where the driver can reach it, and then continues to a ground point. It definitely works, but requires personal intervention. I'll search around for it and get back here.</p><p>EDIT: Here's the fan mod link I found:</p><p><a href="http://www.superstallions.com/tech/cool/fanswitch/fanswitch.html" target="_blank">SSOTN - Misc.- Fanswitch</a></p><p></p><p>Alternately I came up with two ECT sensor mods that turn the fan on at lower temps. They both involve placing electrical resistance in parallel with the stock ECT. The easiest is to add a fixed resistance, the more difficult is to add a second ECT sensor.</p><p></p><p>Keep in mind that the stock fan-on temperature is 221-degrees F while the stock fan-off temperature is 201-degrees F. I found a chart in the service manual that shown how the ECT's resistance varies with temperature. As the temperature goes up the resistance goes down. At a certain low value of resistance the ECU turns on the fan. At a certain high value of resistance the fan turns off.</p><p></p><p>For the adding of electrical resistance in parallel with the stock ECT modification I found that 8.0K-ohms of resistance (may have to be made from several resistors connected in parallel/series, all minimum wattage) in parallel with the stock ECT yields a fan-on temperature of 205 -degrees F and a fan- off temperature of 179-degrees F. This only cost a couple of dollars for resistors from Radio Shack (no longer in business as I understand it).</p><p></p><p>As for adding a second ECT in parallel with the stock ECT , this requires the second ECT to be wired in parallel electrically with the stock ECT, <em><strong>AND </strong></em>immersing it in the coolant system. Electrically this exactly reduces the ECT resistance to one-half of just a single ECT sensor. This makes the ECU think the coolant is hotter that it really is, so he fan turns on at an actual lower coolant temperature. In fact fan-on is 180-degrees F while the fan-off temperature is 162-degrees F. This is the mod I eventually went with. As I have a Vortech supercharger the ECT sensor is conveniently located on the crossover tube right in front and up top in easy reach. I tapped into the cooling system's coolant with a tee fitting into the crossover tube's bong, re-located the stock ECT sensor to one end of the tee's crossmember and added the second ECT sensor to the other end and hooked its wires into the respective stock wires. All tolled it cost me about $65 as I recall.</p><p></p><p>Physically mounting a second ECT sensor to a stock engine I know nothing about.</p><p></p><p>Here's the fan mod link incase you missed it above:</p><p><a href="http://www.superstallions.com/tech/cool/fanswitch/fanswitch.html" target="_blank">SSOTN - Misc.- Fanswitch</a></p><p></p><p>Also, if you are lowering the fan-on temperature you need to lower the temperature of the thermostat. Here's a 180-degrees F unit available from NAPA:</p><p><a href="https://www.napaonline.com/en/p/MRD109" target="_blank">https://www.napaonline.com/en/p/MRD109</a></p></blockquote><p></p>
[QUOTE="SNAKEYE, post: 15951259, member: 22534"] There is a switched ground wire mod to manually switch the fan on as long as the switch is left in the on position. A certain wire coming from/going to the ECU is tapped into and run to a switch conveniently mounted where the driver can reach it, and then continues to a ground point. It definitely works, but requires personal intervention. I'll search around for it and get back here. EDIT: Here's the fan mod link I found: [URL='http://www.superstallions.com/tech/cool/fanswitch/fanswitch.html']SSOTN - Misc.- Fanswitch[/URL] Alternately I came up with two ECT sensor mods that turn the fan on at lower temps. They both involve placing electrical resistance in parallel with the stock ECT. The easiest is to add a fixed resistance, the more difficult is to add a second ECT sensor. Keep in mind that the stock fan-on temperature is 221-degrees F while the stock fan-off temperature is 201-degrees F. I found a chart in the service manual that shown how the ECT's resistance varies with temperature. As the temperature goes up the resistance goes down. At a certain low value of resistance the ECU turns on the fan. At a certain high value of resistance the fan turns off. For the adding of electrical resistance in parallel with the stock ECT modification I found that 8.0K-ohms of resistance (may have to be made from several resistors connected in parallel/series, all minimum wattage) in parallel with the stock ECT yields a fan-on temperature of 205 -degrees F and a fan- off temperature of 179-degrees F. This only cost a couple of dollars for resistors from Radio Shack (no longer in business as I understand it). As for adding a second ECT in parallel with the stock ECT , this requires the second ECT to be wired in parallel electrically with the stock ECT, [i][b]AND [/b][/i]immersing it in the coolant system. Electrically this exactly reduces the ECT resistance to one-half of just a single ECT sensor. This makes the ECU think the coolant is hotter that it really is, so he fan turns on at an actual lower coolant temperature. In fact fan-on is 180-degrees F while the fan-off temperature is 162-degrees F. This is the mod I eventually went with. As I have a Vortech supercharger the ECT sensor is conveniently located on the crossover tube right in front and up top in easy reach. I tapped into the cooling system's coolant with a tee fitting into the crossover tube's bong, re-located the stock ECT sensor to one end of the tee's crossmember and added the second ECT sensor to the other end and hooked its wires into the respective stock wires. All tolled it cost me about $65 as I recall. Physically mounting a second ECT sensor to a stock engine I know nothing about. Here's the fan mod link incase you missed it above: [URL='http://www.superstallions.com/tech/cool/fanswitch/fanswitch.html']SSOTN - Misc.- Fanswitch[/URL] Also, if you are lowering the fan-on temperature you need to lower the temperature of the thermostat. Here's a 180-degrees F unit available from NAPA: [URL]https://www.napaonline.com/en/p/MRD109[/URL] [/QUOTE]
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