1992 Civic Ex 1.6 4dr

After FINALLY stopping a coolant leak at my Water Neck yesterday, after installing a new radiator, I went on to inspect further problems related to overheating and poor performance. I found today that my cooling fan doesn't come on but my temp gauge stays just below the fifty percent mark. I took 12volts to the fan motor and it spins like a champ. Swapped the 12v relay with the other two from the same box; no difference. Followed the wire from the shroud all the way back to the relay box and from what I can see externally it looks normal. Checked continuity from the fan terminal to the relay socket and I had continuity. Thermostat was replaced before I purchased vehicle, however, that might be it? Also I believe there is a seperate cooling sensor that runs into the Water Neck (part with bleed valve and upper rad hose connecting to). I disconnected the terminal there and cleaned it up a bit. Still no fan. I remember a couple months ago thinking my fan was out after letting it idle in the driveway for around 10mins. I live in Texas so heat isn't something I usually have to wait for. The fan didn't come on so I decided to go run it around the block thinking the temp wasn't high enough to send the voltage through. When I came back home after a short trip the fan was on and I was lost. Figured civics were a little different than my 88 suburban and don't come on nearly as soon. With that on my plate I tried not to worry about it, till today. I drove it around the block and even further yet, no fan.

So these are my current theories: Thermostat? Coolant Temp Sensor? (i think i have one) Or something else? I also understand that both these parts are value priced but I'd really like informed advice. Thanks for your time - Dash
(aka newb mechanic)

P.S. My upper rad hose is very hot when running though I realize I should go check the bottom one. If you need more information I'll try and provide.

 

********UPDATED INFORMATION**********
I replaced the fan switch, temperature switch, and temperature sensor today. I let the car idle for about 10mins and the fan kicked on but only at the 3/4 mark on the temperature dial in the car. Then once it dropped it back down just below that mark the fan kicked off. Assuming this reading is accurate, could my thermostat be the culprit? It is the only thing I have not replaced. It is 7months old. Thanks.

 

The thermostat only controls the temperature of the engine, it has nothing to do with the fan turning on. I'm pretty sure that the fan will turn on when the coolant temp sensor says that the temp is above a certain point. I'll look up the wiring diagram of your coolant system when i have time and tell you what i think you should check for next.

Edit: I checked out the schematic for the coolant fan real quick and it turns out that the coolant temp switch determines if the fan should turn on. The switch will be closed when the engine temperature is above 169°-203° F. When you think the temp is above this number, goto the switch and check the voltage drop (leads across the 2 wires going to the switch). The voltage drop should be 0V since the switch is closed. There is a green wire and a black wire coming from the switch. You should also check the relay. There is a black wire with a green strip on the coil side of the relay. There should be 12V when the switch is closed. (this should prolly be done first). Next, check the switch side. I think the switch side uses the Black/yellow and the black/red wire. The voltage here should be 0V. Next check the ground of the of the motor. Black wire from the motor to a body ground. The voltage drop should be 0V here. Also you might want to check the ground of the temp switch. The black wire from the switch to a body ground, Voltage drop should be 0V. If you need any more help or the schematic just ask.

 

Thanks for your input. I was out of town all week due to work and I will take your suggestions and try them out tomorrow.