Honda Gurus - 1990 Civic CX fan switch question

[War_Wagon]

I have no idea why I am having so much trouble finding the answer to this question, it's one of those things that if you google it the majority of things you find on it are for 4th gen Civics with motor swaps etc, and the shop manual I have is total crap.

Bone stock 1990 Civic CX with a 1.5L. The radiator fan is not kicking on. Tested the fan and it works. Tested the wires coming into the fan and there is no power going to the fan even when the temperature gauge is almost off the top. So, my question is simple - what switch actually sends power to the fan? There is the single wire temp gauge sensor under the distributor, and the dual wire temp sensor beside it. But if I jump the dual wire one all that happens is the check engine light comes on, the fan does not. I have checked all the fuses and they are fine, and there is no relay marked for the fan in the box 'o relays under the hood. So, does the ECU get a signal from one of the sensors and then sends power to the fan, or am I missing something totally obvious here? My poor old Civic is ghetto enough with the missing stereo / dash center etc, I hate to have to add to that by hanging a toggle switch off the dash and hard wiring the fan to it!

[cbaber]

Try following the tests described here. I believe there is a relay according to this post.

89 civic Si-cooling fan does not come on ... - Honda-Tech

[War_Wagon]

Thanks for the link. The thing is I think the 1.5 and the 1.6 might have the sensors in different places. The only thing above the oil filter on the back of my block is the oil pressure sensor. And the only thing that even looks like a relay on the passenger inner fender is a little white box with 4 wires going into it, but my more mechanically able than I am friend said he didn't think it was a relay, and the wires all disappear into the harness so you cant follow them. It's starting to get hot around here, I don't want to get stuck on a bridge somewhere and be "that guy" that you hear about on the traffic reports that stalled and held everyone up during Friday rush hour ha ha. I guess I could pull the white box out and just jump the wires to see if the fan comes on?

[cbaber]

I think this one might apply to your 1.5:
Radiator fan not running. Help! - HondaCivicForum.com

There is a relay somewhere, the fan operates at too high current to be run without one. If you know the fan works on direct power but doesn't turn on when the thermoswitch is jumped (key ON) then its either that or the relay. In my case it was the thermoswitch but its free and easy to test the relay before you buy a part you may not need.

[War_Wagon]

Ok this is getting bad. Can anyone here post a picture of the fan relay and it's location for an '88-'91 Civic with a 1.5L? I don't know how my car has been messed with over the last 24 years, but I have found some weird wires that go nowhere and but connectors in random places, and still can't find what the manual says should be the fan relay. Mine is a CX which is the Canadian version of a US STD model if that makes a difference. Thanks!

[California98Civic]

EDIT: FOUND IT.

These are from the 1988-1990 CRX FSM pdf I have in the collection I made while doing transmission specs research. This is for the SOHC version, but I think the 1.6L. Closest I have.

[War_Wagon]

Just saw the edit. Ya, my car doesn't have the relay there. The picture looks exactly the same with the box to the left of the relay and all, but there is no relay in my case. And no hole in the inner fender where the relay should have been bolted to. I ended up parking it for now, I need at least one car that can sit in traffic with all the running around I do. Sadly, it looks like it's going to be a 2003 Yukon. Gah! Can't someone save me from this 12 MPG nightmare? ha ha

[War_Wagon]

Ok NOW this is getting weird. I had to start using the car again, so I was determined to figure out what was wrong. There are 2 wires in the wiring harness at the back of the block that have been cut and had but connectors with nothing attached to them. A 1.6L apparently has the temp control switch that starts the fan at the back of the block above the oil filter. I didn't know if a 1.5L was the same or not. "Ah ha!" I thought, I bet someone snapped the switch off or something at some point which is why I can't see it behind the oil filter, then just cut the wires to it and had put in a switch at some point. So today I put the car up on the hoist and changed the oil, sure I would find a broken off switch on the back of the block. Nope.



You can see the oil pressure sensor switch above where the filter goes, but that's it. And the two cut wires come out of the harness in that area. And if I hard wire those two together, the fan is on constantly. So they control the fan. But what in Honda's name were they supposed to attach to?? I have left the fan on constantly for now even though I can already hear my alternator complaining, as well as my MPGs. But it's too hot here to risk getting stuck in traffic without it so until I wire in a switch or answer this mystery once and for all it'll have to do. Ah, dealing with 24 year old economy cars that have been hacked together to keep them running over the years, is there anything I'd rather do with my time?? ha ha

[California98Civic]

If it was not a CX and if you hadn't mentioned that there was no hole in the fender for the fan relay, I would suspect that somebody had done some swapping of parts at some point and maybe tried to put it back to OEM before selling it, missing some elements. That might be part of what's going on. Maybe somebody replaced the wiring harness, getting it from a CRX or something. Since it is CX chassis, I wonder if it ever had the relay in any location. The CXs seem to have been a trim Honda reserved for a more inexpensive fuel economy: they never get vtec-e but they always get the vtec-e trim's tall gearing, for example. I don't know. Just guessing. But you need a Honda FSM manual covering the CX trim, or a very helpful Honda dealership with a full database of parts for this trim. CX block/chassis and CRX harness?

[dirtydave]

Just put the fan on a switch to the dashboard.