I have a 1991 Civic DX with a 1992 D16Z6 motor from a Del Sol with a half size Skunk2 Alpha half size radiator and single cooling fan, recently my radiator cooling fan stopped working and after doing some quick looking I saw it blew the 20amp fuse along with melting the fuse holder so I figured I would fix it properly instead of the way the previous owner had made it work.

So when I bought the car the previous owner had wired a toggle switch next to the steering column that had the positive wire run directly towards the positive battery terminal and the negative wire run to the fuse holder then to the fan and the fan to the negative battery terminal. It had worked perfectly until the other day so I never really bothered with it (if it ain’t broke don’t fit it). After looking around the engine and on the forums here I think I located the Radiator fan switch on the thermostat housing (no connection to it that I can find, been like that since I bought the car).

Now my question is,
1. Where the hell did the wires and socket go?
2. How do I go about wiring in the proper socket into the car so the cooling fan will turn on when it’s supposed to?

I took a bunch photos of everything I thought would be helpful including a photo of a large 2 prong socket that was tucked away and hidden from me it has 3 wires sticking out blue/red dots, black/red dots, red/black dots that run into 2 relays right behind my headlight assembly. That socket is too large (I believe) to fit on the Cooling fan switch and it is too short to reach back to the thermostat housing. That plastic conduit runs all the back to the firewall where the hookups are for A/C which my car does not have

I’m completely new to Hondas and electrical wiring aside from installing a stereo and speakers. Thanks for any help!



Full view of engine bay

Better look at radiator and fan

Radiator Fan Switch on thermostat housing

Radiator Fan Switch

The definition of “quick and dirty” wiring job to run the fan off the toggle switch

Random socket and wires I found tucking inside the Air cleaner box. 3 exposed wires Black/red dots, Blue/red dots, Red/black dots

Inside view of mystery socket

2 relays that the mystery socket run into

Mystery sockets conduit run towards the fire wall, into the fire wall where the old A/C hookups protrude

 

The fan switch on a 1991 Civic was on the center rear of the engine, unlike the Del Sol where the fan switch was on the thermostat housing.

The 1991 Civic had a connector with a Yel/Grn wire and a Blk wire.

 

I don’t see any connections on my car with that connector wire color combination, I would venture to guess the previous owner also changed the wiring harness when he did the engine swap, according to the previous owner he changed it from DPfi OBD0 to MPFi OBD1 if that helps any at all.

that being said any ideas on how to properly wire in my fan with the fan switch that is currently on the engine (on the side of the thermostat picture in the images above)?

 

On a Del Sol, the harness connector also had a Yel/Grn wire and a Blk wire. The connector was probably different shaped than what a 91 Civic had and was in a different location.

On a Del Sol, the Yel/Grn wire ran to the radiator fan relay located inside the under-hood fuse/relay box.

The harness and wire set-up currently in your car probably is not like either the Del Sol or 91 Civic, since things look in a disarray.

Whatever method you use to get the radiator fan working will likely not be identical to either. You could try to find a used connector that fits the fan switch from a junk yard and wire something in with a relay or directly like what the previous owner did.

 

If you have a much-modified OBD0 harness like I suspect you might, you need to look on the back of the engine under the intake manifold - the original/stock fan switch was above the oil filter, right next to the oil pressure switch. See here, 2nd post: https://crxcommunity.com/viewtopic.php?f=3&t=154833
If the plug is still intact, you'll see the two wires with barrel-style connectors. Some of the weather seal may be left covering the plugs, it's sort of a rubberized cone. More likely it was oil-soaked and fell apart already.

 

If the previous owner has hacked the wiring up, you aren't going to simply be able to plug everything back in. My thermo switch failed on my engine 15 years ago and I also wired the fan directly to a switch. I have no plans to ever put it back and will probably end up wiring it to the ECU to have better control along with having the manual switch. However, the proper way to do with is to run a switch to ground as the thermo switch grounds the coil side of the fan relay to turn it on. So either your fan relay died and the previous owner patched around it or they had no idea how the system worked and just hacked a solution together. Regardless, the fan is one of the highest draws in the cars electrical system. This means it needs a relay (with a flyback diode) and it needs a dedicated fuse.

Sounds like you have a bit of wire tracing to do to figure out what is left of the OEM system and if anything is damaged. Get a copy of the workshop manual for wiring diagrams.

 

i'm not following the OP's wiring mess, but to clarify Tech8's great advice with a picture, the OBD0 coolant fan thermo switch is on the back of the block and located here:



it works passively, apart from the ECU, when it reaches a temperature, it grounds out and turns the relay to the fan on.

and if you want to make a MANUAL override switch, just jump the two leads to this sensor to your own switch. It will work manually, and STILL continue to work passively.

its pretty simple.

 

So after looking again I DID find another switch pictures and label below, but I DID NOT see a second switch with two barrel connections, just the one switch with the one “barrel connector” and a single wire coming out of it. So what I seeing here is that I’m not going to be able to wire the fan up where it will kick on whenever the car gets to the certain temperature? I’m gunna have to wire back up with a switch and relay to the battery?


Switch on the back of the block, under the intake manifold, above the oil filter, SINGLE “PIN” single wire

 

OP here, I probably muddied the waters with too much information, this is the first “import” and first fuel injected car over ever owned so I figured the more information I can give the more help I might be able to get but sometimes keeping it simple is better. I KNOW ABSOLUTELY NOTHING ABOUT ELECTRICAL SYSTEMS in vehicles or anything really, aside from speakers and a stereo and the occasional light bulb.

That being said I’ll check again tomorrow and maybe I just missed the two prong switch by the oil filter but I didn’t feel or see anything else except what I got a picture of that I used on another reply.

And as far as what your saying about still being able to wire in a manual switch as well as it working passively has me confused purely on the definitions of those two words. If I understood you, I can “manually” turn it on and it will run until I turn it off or I can leave the manual switch “off” and once the engine gets to temp if will turn the fan on “by itself” and off again once the engine reaches its lowered temp. Correct?

If so, if there a diagram out there already on how to do this or a video or something?

 

Right, the switch won't be there because this isn't the original engine - you've already identified the switch on the thermostat housing. But if the harness is mostly original, then the wiring should be found back there. The plugs would look just like that single and be only a few inches away.

 

ah, alright let me take a step back and repeat what Tech8 and scelestus and tacocat are saying.

you have a mess of hacked wiring harness. you have an engine from a LATER engine model that does NOT have the radiator fan switch in the same location as the engine that came in your car.

you found the radiator fan switch on the thermostat, you posted a picture of it and labeled it appropriately.

the picture I posted is NOT your engine, you wont find the coolant switch there. honestly, i shouldnt have posted that, its only more confusing for you.

your goal now is to figure out WHICH two wires would have originally gone to the radiator fan switch, and connect them to the connector at the back of the thermostat.

tech8 gave you the colors of the pair of wires you should be looking for.

try TOUCHING two wires together and see if your radiator fan turns on. if the wires are still connected to the relay and fan motor, then it should turn on.

 

I understand, thank you for helping me out with this, I was definitely getting confused to nobody’s fault but my own lol, so thank you, I’ll will have to do some digging around this weekend and post what I have found or figured out. Thank you all again for helping me out!!!