JeffK Posted November 14, 2012 Share Posted November 14, 2012 I need a little imput. Can you activate the cooling fan relay by simply grounding the the wire that goes to the #2 terminal on the connector? Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 14, 2012 Share Posted November 14, 2012 No, not according to the schematic. Pins 2 and 5 are the relay coil contacts; pins 1 and 4 are the load contacts. Since pin 5 is tied to ground, you would have to apply 12VDC to pin 2 to activate the relay. That's what the radiator temp switch does when it reaches the HI set temp. Link to comment Share on other sites More sharing options...
JeffK Posted November 14, 2012 Author Share Posted November 14, 2012 Makes sense, thanks. The temp guage I have uses an adjustable 12v(-) trigger to activate acessories, and I was trying to avoid using another relay. Using the additional relay, this is what I have in mind. Is my thinking on this correct? Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 15, 2012 Share Posted November 15, 2012 What are you trying to do? Activate the electric aux fan with a dash switch? Or with a switched ground through an Autometer gauge? Link to comment Share on other sites More sharing options...
JeffK Posted November 15, 2012 Author Share Posted November 15, 2012 Sorry, I'm using this Autometer guage and I'm eliminating the sensor in the radiator. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 15, 2012 Share Posted November 15, 2012 Sounds like you want to control the aux fan with the switched ground output from the new Autometer temp gauge. Where do you plan on locating the Autometer gauge temp sensor? In the radiator bung where the existing fan temp switch switch is? If so, yes it will work with the existing fan relay, you don't need another relay. Just apply a constant 12V ignition switched voltage to one of the existing fan relay coil contacts, and your Autometer switched ground signal to the other coil contact. The aux fan relay connections will stay the same. The switched ground from the new temp gauge will turn the fan on and off. That's how I control my second electric fan in my rig. Link to comment Share on other sites More sharing options...
JeffK Posted November 15, 2012 Author Share Posted November 15, 2012 The new radiator is for an open system and dosen't have the temp sensor bung. I had already bought a late model t-stat housing and I mounted the sensor here... So run the constant switched 12v+ to the #2 and the Autometer ground to #5? But won't 12V+ to the #2 make the fan fun all the time? Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 15, 2012 Share Posted November 15, 2012 So run the constant switched 12v+ to the #2 and the Autometer ground to #5? But won't 12V+ to the #2 make the fan fun all the time? That's correct. The fan will not run until it receives the switched ground from the Autometer temp gauge. When the ground is appplied to relay pin2 (preset by your temp setting on the gauge), the relay coil energises, closing load contacts 1 and 4, and applies a ground to the fan motor, then the fan motor runs. When (if) the coolant temp goes down, the thermostat temp sensor opens, the ground to pin 5 is removed, and the fan turns off. It's going to take time to get it all adjusted right, but should work just fine. Link to comment Share on other sites More sharing options...
JeffK Posted November 15, 2012 Author Share Posted November 15, 2012 Good stuff, so if you were to run an override switch, would you do the same except substituting a switch for the guage? BTW, thanks for the help, you saved me a lot of time over trying to figure this out on my own. Link to comment Share on other sites More sharing options...
Eagle Posted November 15, 2012 Share Posted November 15, 2012 Good stuff, so if you were to run an override switch, would you do the same except substituting a switch for the guage? BTW, thanks for the help, you saved me a lot of time over trying to figure this out on my own. A manual override is much easier. On your schematic, do you see the original radiator sensor? It's a switch. You'll be abandoning it anyway, so you should have a two-conductor plug where the bung sensor connects to the harness. Just plug two wires into that plug and run them to your toggle switch. Link to comment Share on other sites More sharing options...
JeffK Posted November 15, 2012 Author Share Posted November 15, 2012 Sounds like a good back up for the guage, thanks. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 15, 2012 Share Posted November 15, 2012 Good stuff, so if you were to run an override switch, would you do the same except substituting a switch for the guage? BTW, thanks for the help, you saved me a lot of time over trying to figure this out on my own. I'm assuming you would want a manual override switch in case the switched ground from the Autometer temp gauge craps out? If this is the case, Eagle's suggestion to add a switch in place of the original radiator temp switch will do nothing because it switches the 12V IGN switched supply to the relay coil. This supply is to be wired constant. You want to switch the ground signal on the other side of the relay coil, because that's what you would lose, not the constant 12V IGN switched supply. I would add an additional dash switch that would apply a ground to pin 5 of the fan relay, because if the switched ground from the gauge were to blow, you could still turn the fan on manually by applying a ground to the relay coil with the dash switch. Make sense? Also, if you have A/C, you realize that by using the switched ground from the Autometer temp gauge you are changing from a switched 12V to a switched ground to turn on the fan relay. This will cause the aux fan not to come on automatically as should when you turn the A/C on. The aux fan won't come on until the relay receives the switched ground from the gauge that is dependent on how you set the gauge trigger point. Link to comment Share on other sites More sharing options...
JeffK Posted November 18, 2012 Author Share Posted November 18, 2012 hornbrod, eagle I appreciate the input. What I ended up doing was using a relay wired like diagram below. Worked like a charm. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 18, 2012 Share Posted November 18, 2012 Okay, I can see how that will work. You're using the switched ground signal from the Autometer gauge to trigger the new relay. When the new relay latches, it applies a ground to the original fan relay pin 2 to turn on the fan. Do you have A/C? Link to comment Share on other sites More sharing options...
JeffK Posted November 18, 2012 Author Share Posted November 18, 2012 Yes, but when it latches it applies 12V+ to #2. Hey thanks for the help digging through this, not a lot of info on this out there. Link to comment Share on other sites More sharing options...
HOrnbrod Posted November 18, 2012 Share Posted November 18, 2012 I see that now on the OEM schematic that there were originally two 12V inputs to fan relay pin 2; one from the original radiator switch, and one from the A/C controls. Installing the additional relay as you did did not affect the A/C switched 12V. Excellent job figuring out the wiring for that additional relay. :cheers: I'll have to remember that. It's a good way to transition from switched 12VDC to switched ground and vice-versa. The HOs are completely different as they use switched grounds from the A/C and the temp sensor to turn the fan on, not switched 12V inputs since the signal goes through the ECU computer. Link to comment Share on other sites More sharing options...
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