Main coolant fan not working

[pauleyman]

Ok I'm stumped. Ac fan works as it should. I tested every relay by swapping to ac slot so all the relays are good. Jumpered main fan (lo) and (hi) under the relay and it comes on so fan is good and wiring to fan is good. Scan tool reads coolant temp fine so sensor and harness are good. Temp hits 200 plus and fan never comes on. It overheated yesterday. Only thing left is wiring to relay to trigger it and ecu i think. Maybe a ground somewhere? This is all after a head swap. Several days after head swap it popped a radiator but that was probably because it was overheating and son didnt notice. Bring on the suggestions before I tear apart something unnecessarily.

 

[19Eclipse90]

Grounds are fine else the fans wouldn’t work when the relays were bypassed. Grounds 1 and 3.

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Power side for the radiator Hi and Lo relay coils shares common with the condenser fan Hi relay. Since these are all in the relay box, I expect they should be fine.

The grounding side of the radiator Lo relay goes to ECU pin 21. The grounding side of the radiator Hi and condenser Hi relays goes to ECU pin 20. You can check continuity across those to the ECU if you want to be thorough. I’d check the contacts in the fuse box itself to make sure they are clean and haven’t pushed down into the fuse box.

So, you tried both radiator relays in both condenser relay slots? And verified the condenser fan goes both high and lo?

I doubt you undid connector A-32 for a cylinder head job, front and engine control harness combination, but double check that connection and the wires are all seated properly.

I think I have a spare ECU if you wanted to try that.

 

[1990TSIAWDTALON]

Crossing my fingers it is just a bad connection but with that fan not working on low or high, sure seems to point back to what triggers them Paul.

 

[pauleyman]

Grounds are fine else the fans wouldn’t work when the relays were bypassed. Grounds 1 and 3.

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Power side for the radiator Hi and Lo relay coils shares common with the condenser fan Hi relay. Since these are all in the relay box, I expect they should be fine.The grounding side of the radiator Lo relay goes to ECU pin 21. The grounding side of the radiator Hi and condenser Hi relays goes to ECU pin 20. You can check continuity across those to the ECU if you want to be thorough. I’d check the contacts in the fuse box itself to make sure they are clean and haven’t pushed down into the fuse box.So, you tried both radiator relays in both condenser relay slots? And verified the condenser fan goes both high and lo?I doubt you undid connector A-32 for a cylinder head job, front and engine control harness combination, but double check that connection and the wires are all seated properly.I think I have a spare ECU if you wanted to try that.

I did not check AC high as you can't unless you're coolant temp is high. I did all tests with cold car.