widebody91hatch

I have been messing with this dx civic for about 3 days and i'm pulling my hair out...

the car recently blew a head gasket and has since been changed (by somebody else) and the cooling fan is not coming on (i do not know if the fan worked prior to the blown head gasket but my guess is no). I have checked fuses, power and ground all over the place, swapped relays, changed cooling fan switch, and changed the thermostat (was stuck shut).

I have 2 powers (one constant and one signal) and 2 grounds at the fan relay with the key on. i have ground at the harness connector to the fan. i have manually jumped the fan and it does have the ability to work but i currently am not getting power to the fan. this car is driving me nuts.

My questions are: Does the pcm control power to the fan? will the coolant temp stop the function of the fan even though the guage is reading properly?

I know somebody has run into a similar situation and i just need a direction to go. If anybody can give me a wiring diagram or a pcm pinout then i may be able to further my search but as of right now i am confused

Fabrik8

Remove the relay and check the voltages without it.

Have you checked the fan temp switch?

SmokeCRX

+1

remove connector from fan switch on thermostat housing with key on and jump the two wires. If the fan starts....the switch is bad.

widebody91hatch

UPDATE: I have now changed coolant fan switch, coolant temp sensor, fan relay, and tried a different ecu out of a running car and nothing has changed... i still have no power to the fan... i really need a break down in wiring to the fan cuz i have power and ground to the relay and the fan switch and i'm not sure in what order these parts fall on the way to the fan... trying to find a good wiring diagram that shows everything cuz i don't know what other parts to throw at it and i'm not going to just run a jumper wire cuz thats not gunna fix my problem

Fabrik8

Replacing everything you can think of is not troubleshooting.

You need a factory service manual, and not the shitty Hanes or Chilton manuals.

There are PDF Helms manuals for your car all over the internet, Google and see what you can find.

boostedb16

cut the plug off the thermostat sensor and solder the green and black together then tape up good. it will cut on and off with the key

basketthis69

Have you checked your fan fuse for corrosion? This happened to me in my 94 integra. Drove me crazy. Even with a multimeter it was VERY difficult and time consuming to find. I suggest you get a meter and have some idea of what you are doing... You can start at the fuse panel under the hood. If you have power there, just go down the line until you find something without power and you will find the problem by process of elimination. It really is easy if you have the right tools... GL

SmokeCRX

Stop throwing parts at it...test it. Fuse 13 in under dash fuse box powers the control side of the relay. Fuse 33 in under hood fuse box powers the switching side of the relay. The control side can either be grounded by the switch (in thermostat housing) or by the ECU. When control side grounds...power is sent to the fan. Thats all there is...I'm lookin at the factory manual right now. lol. With the key on...When u jump that switch... u should have two powers and two grounds at the relay. Power to the fan comes directly from the relay. if you have two powers and two grounds with the switch jumped... look at the relay (it shows which pin is which) and jump power from one of the powered pins to the ground of the switching side. The fan should start moving. If it doesnt...you have a break in the black/red wire goin to the fan.

widebody91hatch

Thanx SmokeCRX... that is what i was looking for.. i work in a shop and i use mitchell online for my diagrams and other various things but the diagram it shows is messed up and doesn't make sense thats where i got confused from the beginning and the way everything happened led me to believe either the pcm or temp sensor wasn't doing its job so i tried taking the pcm from another car and it didn't work so i threw a coolant temp at it hoping it would magically work because i had no accurate wiring diagram showing in which order the wiring went through these parts... but now i know that power comes directly from the relay and i am going to check continuity of said black/red wire and find out if there is a break... cuz what confused me at the relay was that i had 2 powers and 2 grounds at key on engine off when i would have figured that the signal power would have not been introduced until it was time for the fan to come on but i guess i must start all over from square one.... thanx guys... i will update with anything i find or other problems i come accross

widebody91hatch

it sucks working on a car that somebody else who had no clue what they were doing had their hands all in... shit he might have fucked something up when he did the head gasket.... we'll see