I drive a 2000 civic ex, and I noticed today my car was overheating. I checked the hoses, didn't lose any coolant, but realized my radiator fan wasn't spinning, even when my temp gauge was nearly maxed out. My A/C fan also isn't working. I replaced the thermostat and the fan switch, and still no go. I was wondering if it was the fan relay in the distribution box, because I checked the underdash fuse and it was fine. Anyone know how to diagnose the problem, or to check if the relay is bad?

**EDIT** I also wired the fan straight to the battery, and it works just fine when I do that, so does that mean its either the relay or the wiring?

 

unplug the fan switch (2 wire, screwed into the thermostat housing). Jump the connecter with a short wire or paperclip or something. Listen carefully, you should hear a faint click from the under-hood relay/fusebox and the fan should come on. This pretty much checks out all the wiring in the system.

are you getting a CEL?

 

When you jump the switch, you will also have to have the key on (but not necessarily engine running) before the fan will run.

 

So I jumped the switch and still the fan does not turn on, does that basically leave the relays to blame or could it be something else?

**EDIT** and no I'm not getting a CEL, the guy at my parts store said that most of the time if its a relay it wont turn on the check engine light

 

Yes, check the fuse and relay in the fuse box. Look for melted contacts in the box, if that's the case the whole box will need replacing (actually not real expensive). Swap the relay with one of the other ones, there several in there all the same type.

 

So I bought a new relay and fuses and replaced EVERYTHING, and its STILL not working. I don't know if I mentioned this earlier but my A/C fan isnt blowing either. I'm wondering if that has something to do with it. Do they have anything to do with each other? This project is driving me crazy and I just wish I could figure out the problem.

 

Someone posted the diagram a while ago. Power for the relay coils comes from a fuse under the dash (live only when the key is on). Though I would think that if that fuse were blown, there would be other symptoms. Pull the relay out, turn the key on, use a meter or test light to verify that one coil terminal and one contact terminal in the socket are live.

Also check the power circuit, when you jump between the two contact terminals (key on or off), the fan should run. If not leave the jumper in and probe the wires at the fan (fan still plugged in). If both are 12 volts relative to ground there is a problem in the ground circuit.