STR8V8

Hi all,

New poster, longtime lurker of these forums. I have a 99 Honda Accord EX V6 3.0L Sedan 286k miles and noticed this past week the car was running a tad hotter than normal. Popped the hood and noticed the cooling fan never came on (this car has two, referring to the radiator one) and if I let it sit there long enough the A/C fan would kick on but not the cooling fan. Did some tests and determined I had a bad fan so I swapped it out this weekend but the issue still persists to where the cooling fan is not turning on via temperature. If I turn the A/C on both fans *WILL* come on.

My buddy recommended I unplug the ETC sensor after the car warmed up to see if the fan comes on which I did, and the cooling fan does not come on. The car seems like it pulls timing or makes a quick adjustment because the entire tone of the car changes when you unplug this sensor while the car is running.

I tested the plug going into the radiator fan and I am getting proper voltage to the connector. I took the radiator cap off and noticed that coolant is not circulating inside the top of the radiator like it normally does and the bottom radiator hose is cool/luke-warm to the touch. The car is NOT overheating while I drive it or idle, but it is using coolant which is apparent by markings I've done on the radiator reservoir and I've had to top it off twice now.

The car has a new radiator, new upper radiator hose, I *THINK* the thermostat was replaced but I can't remember if I did it or not (leaning towards I did with an aftermarket) new waterpump assembly/timing belt a year ago, and the radiator fan itself was replaced. Can anyone guide me on what else I can check to determine what could be causing this? I can obviously drive the car with the A/C on and get by, in fact I can drive it fine without the A/C (radiator fan) it just runs a tad warmer than usual. I am worried with hotter temps around the corner the car is going to overheat. If there is a plug/sensor I can try to bypass or jump to do a test, or a voltage reading I can take please let me know as I am completely out of ideas. I was thinking this was thermostat related but it doesn't make sense to me why the car would only be running a tad warmer. I am about 3-5 tick marks on my temp gauge off from normal temp.

For reference, I was thinking I have a blow headgasket and while I have some white smoke on startup, I am 90% sure this is due to condensation in my mufflers as it goes away after the car reaches operating temperature and nothing is coming out of the tailpipes but water.

Thanks for any help in advance!

tech8

1. For a 99 Accord V6, Fan Switch A (located on the thermostat housing; look under the throttle body area) should turn on both cooling fans when the coolant temperature is above 199 degrees, with the engine running.

To test that the wiring is okay from Fan Switch A, unplug the electrical connector and jump the connector's terminals with a wire or small paper clip. Turn ignition to ON, both fans should come on.

2. If both fans come on by jumping the connector to Fan Switch A, then issue can be due to: faulty Fan Switch A, or air in cooling system, and/or low coolant.

STR8V8

Evening Tech,

I just tried what you said and put a medium-sized metal paperclip into the plug and turned the ignition to on (right before cranking the car) and neither fan came on. Does this mean the electrical plug itself is bad and not the switch? Could the relay be bad or does jumping it rule that out? I just checked the fuse for the cooling fans and it is fine under the hood and I pulled the relay and nothing looked "odd" other than some slight discoloration on one of the pins. I saw there are several other relays that are the same model/part number, could I try swapping that with say the condenser relay just to test?

Thanks for the reply and continued help!

tech8

If both cooling fans run with the A/C on, the relays are fine.

With the electrical connector to fan switch A unplugged, run one end of a spare piece of wire to the connector terminal where the green wire is and the other end of the spare wire to body ground. With the ignition ON, does both fans run?

If they do, the issue is the wiring from ground G101 to the connector.

Report back the results.

STR8V8

Tech,

Excuse my stupidity, I did a google search for the ect plug and apparently must have had the wrong engine because I was not testing the correct plug. I just did the one in your diagram and the fan came on! So I am assuming we have a bad temperature control switch since the connector works? I am positive I am not low on coolant. Is there any harm in leaving the paperclip in to run the fan or would you recommend just running the a/c since I can control it that way?