fan not turning on?

2012 HYUNDAI TUCSON
140,000 MILES • 4 CYL • 2WD • AUTOMATIC
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BHAMDOC1973
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friend of mine bumped into a wood block on the road which caused it to damage the radiator, the plastic fan was also broken so I replaced both. The fan has a 2-wire connector from the fan motor which connects to a 3-wire connector from the main harness. I waited until it had gotten to optimum temperature, but it didn't come on. I turned the A/C on, compressor comes on, but fan doesn't. I checked the 2 wires from fan with a probe light and both came back negative, maybe until the signal comes in? same with the 3 wires from harness, both red and maybe grey or black wires have ground. not sure where to begin.
Apr 8, 2025 at 7:06 AM
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BHAMDOC1973
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I switched the relays around and it worked. now I need to figure out which one isn't working.
Apr 8, 2025 at 9:24 AM
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STEVE W.
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That has a different system. Both relays power the fan, one is low speed, it feeds power to the fan motor through a resistor, the other is the high speed and it feeds power while bypassing the resistor. The correct fan has three wires, not 2, sounds like someone replaced it with a different fan which could be the issue, if the fan is only connected to the high relay it has to get much warmer to activate. So, figure that out first. They could have connected it to either one.
Then testing is easy, just jumper pins 1&2 in the high relay socket, does the fan come on high? Go to the low relay and repeat the jump of 1&2 in that socket, fan should come on low. To test the rest of the circuits go to the PCM and locate pins 65 and 88. Just ground those with the key on and the relays in place, the fan should come on for both speeds (if it's the correct fan) If the fan works then, unplug the temperature sensor, that should trigger the PCM to turn the fan on high. For low you would run it up to temperature or trigger it with a scan tool.
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Apr 8, 2025 at 2:50 PM
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BHAMDOC1973
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No the resistor is the one with 2 wires to fan on one side and 3 on the other, i even tried the original one, removed it and installed it. They both look the same and online videos show it to be that way for some reason. I'll see if the fan work on all speeds, so far it comes on when A/C is on and comes on when engine reaches optimum temperature.
Apr 8, 2025 at 2:54 PM
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STEVE W.
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Hmm, must be a mid-year change then. The US OE has a single 3 wire harness.
Apr 8, 2025 at 5:29 PM
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BHAMDOC1973
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no even the new fan came with the same resistor.
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Apr 8, 2025 at 5:30 PM
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STEVE W.
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Okay, the resistor is just outboard of the fan, which lets them use a cheaper fan with an adapter. Testing would still be the same as the fan circuit. The relays just route power through that resistor for low speed or it gets bypassed, so the fan gets the full 12 volts. Sort of a neat idea really. Might be an idea to look up the fan itself and see just how much they are charging for that resistor.
Apr 9, 2025 at 9:46 AM