Cooling fan Issue

ostalecki73 said:

Hello please let me know if this has been covered and if so a link would be great. I have a 2001 Civic Lx I just changed the water pump, timing belt, tensor, and oil pan gasket. I put in a new thermostat, cooling fan switch, and ECT sensor, all Honda parts from Honda parts.com. The first issue is the fans aren’t coming on if I jump the cooling fan switch the fans work great, plugged in to switch nothing, (I checked for continuity and it is good from relay to fans, and from ground locations 201, and 301). The second issue burped the system twice, and when I run the car for an hour the upper radiator hose is hot but the bottom is cool, and the radiator is not warm or hot. However, there is hot air coming out in any selection in the cabin, and the temp indicator is below halfway. The coolant is hot, and I replaced the radiator cap, also the coolant is blue with no oil in it, and when I checked the oil, it is not milky or white. And there is no indication of a blown head gasket. Could this be a partially clogged radiator? -TIA

Click to expand...

I'm not sure what the actual complaint is here. Is it overheating? You have heat from the heater core, so it seems like the thermostat is working? The temp gauge is reading the radiator temp and not block temp so it often won't show the problem until things get pretty bad. The fans won't come on unless that switch gets hot and since the water is cold near the bottom, (at the fan switch?) they won't come on.
Do the fans come on when the AC is on? They usually come on as soon as you engage it.

I've seen folks make the super easy mistake of getting the thermostat installed backwards such that the actuator isn't on the hot side, so you might want to check that. I've also seen a bad NEW thermostat that refuses to open all the way. Removing it and testing might isolate it in either of those cases. Note that running without one will result in a cold heater and less efficient engine so if that is it you'll want to fix it proper eventually but removing it will rule it out. You've probably noticed they like to overflow with the top off. If it's got no movement with the top off, that also points to the t-stat.

Hope my rambling helps somehow.

Hello, there is no complaint the question is why won't the cooling fans will not kick on? They only work if the radiator fan switch is jumped. I verified the thermoset opens (put it in 200 deg water), new ECT, fan witch (Ohm out it is opening and closing), new radiator old one was not getting hot no flow, now has flow visual verified with cap off, and it is getting hot as both upper and lower houses are. Drove the car for an hour and a half in stop-and-go traffic and the fans never come on. The temp goes to below halfway never over, also I burbed he system twice and verified the heater core valve opens and closes, the overflow tank is not filling up with coolant., also no milky oil, and clear blue coolant. Side not3 the A/C does not come on at all. I have checked all the fuses they are good, all the relays, and the ground 301 and 201, and ohmed it all out to the ECM and it is all good. I am just looking for some input as I have seen some great tech advice on this form.

If the gauge isn't getting above halfway in stop and go traffic it's cooling okay without them, but I think we're both overthinking this. If they run when you jumper that switch on the thermostat housing then that rules out the entire system, except that thermal switch. You replaced that part with a wire and the fans ran. Whatever the reason, if the circuit works with it bypassed then logically it must be the problem. It could be the wrong temp. range or sticking or who knows what, maybe it doesn't like torque.

With that established, some more obtuse ideas; what if jumpering the connector isn't what made them work, but instead "moving" the connector? Is it clean inside and connecting to the switch well? You might also try wiggling the harness around while checking resistance back to the other end(like you did before) to check for a broken wire in the insulation(possibly also a lead to follow on the A/C fail). I've seen those drive guys nuts, and it was on our troubleshooting final back in college. Above all, once you think you've ruled out all the suspects, suspect them all again(but don't just replace everything like dealerships do)