Jonathan_ED3

My radiator fan will not come on.

The fan works when hooked to 12v.

I uplugged the switch on the thermostat housing and jumped it with the key "on". Nothing. Couldn't hear the relay clicking, and of course, the fan still doesn't come on.

I replaced the relay with a known-working relay out of my daily driver, and still nothing. No relay clicking.

Cooling Fan Relay fuse in the under-dash fuse box is good.

Anybody have any ideas?

r33dm0n3y

check your thermoswitch. it's a little, well not too little, plug by your thermostat. it screws in and essentially has a relay in it that activates your fan when the coolant gets to temp. you can find out if it is your thermoswitch by removing the clip that connects to the thermoswitch and closing the circuit with a paperclip. if your fan turns on, it's your thermoswitch....mine was $54.00 from honda. have a rag handy when you change it as some coolant will leak out. good luck.

Jonathan_ED3

Thanks for the tip, but I already tried that. That's what I was talking about in my first post when I jumped the connector with the key "on".

nsxmatt

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jonathan_ED3 &raquo;</TD></TR><TR><TD CLASS="quote">Thanks for the tip, but I already tried that. That's what I was talking about in my first post when I jumped the connector with the key "on".</TD></TR></TABLE>

Not sure you bypassed the coolant temp switch correctly. The switch is the problem 99% of the time, just replace it.

Jonathan_ED3

I know I'm doing it right. I have this car side by side with my daily driver, and I tried the "jumper" method first on my DD. Relay clicked, and fan came on promptly.

On this car, however, the relay doesn't click and, of course, no fan.

I know the switch is the problem 99% of the time. I'm wondering what to look for the other 1% of the time.

randomtask77

Did you try replacing the temp sensor that is under the distributor?

wdissident

i had the same exact problem if u just stick a wire and connect both sides to the outlet it will just turn on when you turn your key. its not bad

Jonathan_ED3

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wdissident &raquo;</TD></TR><TR><TD CLASS="quote">i had the same exact problem if u just stick a wire and connect both sides to the outlet it will just turn on when you turn your key. its not bad</TD></TR></TABLE>

I would PREFER to get to the source of the problem.

If I have to I will wire up a switch to with its own fuse and relay for the fan, but I want this thing to be all OEM.

bigD

did you check the fuse in the engine bay?

nsxmatt

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jonathan_ED3 &raquo;</TD></TR><TR><TD CLASS="quote">I know I'm doing it right. I have this car side by side with my daily driver, and I tried the "jumper" method first on my DD. Relay clicked, and fan came on promptly.

</TD></TR></TABLE>

There is a fuse, relay, and switch, and wires. That's all. If you are sure you checked it all then your wrong somewhere. Use the switch out of the "daily" and see if it works. There is only 2 switches made from 84-00 Civics Integras, and Accords and all interchange. If it doesn't work switch the relay. If you really want to fix it beyond that, you'll have to probe the wires and actually diagnose it.

cloudconnected85

had a similiar prob just hook up a switch to the fan so you can turn it on at any time so if you race or drive hard you can turn it on early for cooler temps

gsrhatch2356

Ok the circut is pretty simple, on the relay you should have two pins that have 12v both of which come from diffrent fuses so if you dont then start there then on the relay you will see four numbers 1 and 2 are the controller side of the relay and 3 and 4 are the controlled side of the relay. if you jump the pins 3 and 4 the fan should come on. if it does then the problem is on the controller side of the relay. which would be a bad power supply at relay which i mentioned you need two pins at relay with 12v, a bad thermo switch which you said you jumped and nothing happend, or a bad ground going to the thermo switch. if you wanna check for a bad ground take a wire and run it from ground of battery and place in thermo switch connector, only one wire will turn on the fan but if it comes on the other one is the one that is bad. if you jumped 3 and 4 and the fan didnt come on then there is either a lack of voltage at realy or the wire between the relay and the motor are bad. and last but not least the ground coming off of the motor is bad. I hope this helps and pm me if you have any questions I will check back till i see you dont post anymore or say you got it fixed. good luck.

Jonathan_ED3

gsrhatch2356, thanks for the response.

That's what I was looking for - everybody keeps talking about the switch, but they're not understanding that I am bypassing the switch in my tests.

On the relay, I've only got 1 pin showing 12v constant.

Should 2 pins be showing 12v constant?

Or one constant and one key-switched 'On'?

I didn't test it with the key on, I don't think.

When I jump 2 of the pins, the fan does come on. I forgot to say that in my original post. Not sure which number the pins are, but they are they upper left and lower left when looking straight down to the spot where the relay should plug in.

Fan Relay itself is good. Tried two different known-good relays.

The switch on the thermostat housing and the bottom right hand pin of the Fan Relay case both have continuity to ECM Pin A12 (like they should).

The Upper Left pin of the Fan Relay case has continuity to 12v, like it should.

The Lower Left pin of the Fan Relay case has continuity to the fan motor, and when jumped to the Upper Left pin of the relay case, the fan comes on.

I tried using a different ECM, but it's still giving me the same problems.

What part of the equation am I missing here?

nsxmatt

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Jonathan_ED3 &raquo;</TD></TR><TR><TD CLASS="quote">
That's what I was looking for - everybody keeps talking about the switch, but they're not understanding that I am bypassing the switch in my tests.

</TD></TR></TABLE>

I still don't think your testing it correctly. Instead of testing all day, why not swap in the good known one that takes 5 minutes and completely rule it out?

gsrhatch2356

yes you should have two power supplys at the relay and one is only hot in key on engine off or running. the one that is hot on key on is fuse 13 (7.5amp) under dash fuse box, so try that first and see if you can get two power supplys at the relay first. untill then there is no need to look at anything else.

EL Vap133

Check the wiring, we found faulty wiring on my hatch and that would cause my fan not to go on from time to time which would overheat my car. Wiring was bypassed and problem solved thanks to my buddy Ralph!

Jonathan_ED3

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gsrhatch2356 &raquo;</TD></TR><TR><TD CLASS="quote">yes you should have two power supplys at the relay and one is only hot in key on engine off or running. the one that is hot on key on is fuse 13 (7.5amp) under dash fuse box, so try that first and see if you can get two power supplys at the relay first. untill then there is no need to look at anything else.</TD></TR></TABLE>

There is no power at fuse 13, or key-on at the relay.

There is a constant 12v supply at the relay (upper left terminal, if looking directly at underhood fuse box), but there is no switched-on (key-on) power at the relay.

I'm having a hard time finding where fuse 13 circuit originates -- some of my wiring diagram is missing.

EDIT: Turned out to be a faulty wire at the ignition switch.


Modified by Jonathan_ED3 at 1:12 PM 9/27/2008

gsrhatch2356

ok at this point I have only been assuming that this is a eg. but jusat to make sure you should let me know, most of the wiring is the same but some of it is diffrent. any way the diagram I am looking at shows from battery to fuse 41 under the hood (80 amp) then goes through another at fuse 39 under hood (50 amp) then comes out of fuse box as wht\blk then turns to white at ignition switch (this is just the power to the switch and if this was the problem then the car wouldnt start) at the underdash fuse box you should see a yel wire this comes from the ignition switch and is the power to the fuse box. if there is no power on the yel wire at ignition switch then you need a new switch. if there is follow it down to the fuse box and check it there. if there is power there then remove the fuse box and open it up there is a problem in there that is not allowing power to go to the fuse. but if for some reason you may have the wrong fuse or you have a ek and it is diffrent. sorry I just went and checked, all the wiring colors are the same but it is fuse number 17 on a ek still (7.5amp) so try those things and let me know.

Jonathan_ED3

Yeah, it's an EG.

The problem was with the yellow wire coming off the ignition switch. It had a break in it and the fuse box wasn't getting power for those circuits. I repaired it, and now everything is good to go!

Thanks so much for all your help!

gsrhatch2356

well I love to hear that you fixed it and stuck to getting the job done right without changing the wiring or putting in a switch to cut out the thermo switch.

_MARS_

What would cause the cooling fan fuse under the hood to blow? [ other than the obvious! ] like, power wire touching ground!

redline8000

I have a problem with my 99 civic dx with b18 swap. There is two connectors by the ect, both can plug in, when one is plugged in the cooling fan will NOT come on and them computer will see engine coolant temp and adjust fuel trim but remember that the cooling fan will not come on. With the other plug connected the fan comes on as soon as koeo but the computer shows fault in ect and sets fuel trim to adjust to-40 degrees belowe zero. It's causing a me to run extremly rich and killing gas mileage. Honda gear heads please help.

D16SiHatch

the connector on the side of the cylinder head is the ect sensor for the ecu. the switch on the thermostat housing is what engages the relay to turn the fan on.

redline8000

I'm lost the thermostat housing has wires grounded to it. No sensor plug in. Bout to run toggle switch and push button start. Should I even worry about it as long as I can get my ecu to see coolant temp?

D16SiHatch

you must have an obd0 b18 then huh. if that's the case, your fan switch is located on the back of the block. looks like this. its the 2 pronged dealy with nothing plugged into it.