Ok Honda guru's.... need some help

First off, this car is completely stock. 1998 civic LX D-series. My problem is that the radiator fan is not turning on. The temp gauge can start climbing until I put the heat on full blast to bring it back down but at no point does the radiator fan come on. I’ve done a fair amount of troubleshooting to this point with no luck.

First, it has a new ECT switch (the one on the thermostat housing). I can unplug that switch and jump the wires and the fan turns on. So that tells me that the relay is good, and the fan motor is good. For the heck of it I originally swapped the relay with the A/C fan relay, and the A/C fan still turns on. So definitely not the relay. Now its my understanding that if the relay is good, the fan motor is good, and that ECT switch is good… those are the 3 components that tell the fan when to turn on? Am I missing something else? Oh and all the fuses (underhood and underdash) are good. I know there are two other temperature sensors on this motor but one is solely for the gauge cluster and the other is the signal for the ecu regarding fuel trim etc?

As a last resort I can just run a toggle switch but I’d really rather have it working the right way. Any thoughts are definitely appreciated thanks.

note* the A/C compressor clutch isn’t engaging but I haven’t really looked into that yet, most likely unrelated but figured I would throw that out there maybe someone knows something I don’t lol

Recently changed or added coolant? If so it could be an air bubble in the coolant system

Say fuck it and run an aftermarket fan switch?

You don’t want a cooling fan on all the time

Actually yes I did just recently change the coolant, I had to replace the radiator/thermostat. I honestly don’t know if the fan was working prior to that however. I’ll follow the honda manual this time for the coolant bleeding.

And not sure who said to put the cooling fan on all the time? Thats why I said as a last resort I’d use a toggle switch as needed. keyword last resort lol

Pm carnut (don).

i can almost guarantee there is an air bubble at the switch causing it not to work. bleed the system again

I assume you could just use a OBDII scantool and read the ECT temp because the fan should come on at a set temp.

I believe the temp sensor it’s in a different location than the switch

Jay, sounds like you have air stuck in the cooling system. Bleed the cooling system and see if that fixes your problem. If the fan worked before the repair it should work after the repair.

^this is correct.

like everyone else said, it’s either air at the fan thermoswitch, or you got another broken thermoswitch (which you could test by boiling some water and dropping the sensor end in it and check for continuity across the two leads.)
Basically your problem is super minor if when you jump the connector at the harness the fan turns on, so that’s a good thing.

edit: check you harness side for corrosion at the pins where the thermoswitch connects too…perhaps your jumper wire makes good connection but the pins coming out of the sensor just hit badly correded contacts.

Same thing happened to me on two separate hondas. There’s most likely an air bubble if the fan switch and thermostat are good. Just pop the cap off the radiator and run it until all the bubbles are gone and the fan comes on twice, it may take a while, just watch the temp gauge.

Ok I bled the coolant yesterday, and after a good 40 minutes (doesn’t that seem long?) the fan finally kicked on. For good measure I let it run a little bit longer and it came on again. So kudos to everyone who said air bubble!

This car has had a host of issues (good thing it was cheap lol) and now I’m still dealing with a starting issue. Some times I can go out to the car and it starts right up no problem. Other times I can try to start it and it will start, but run really rough/low rpms for about 5-10 seconds then clear itself up. Other times it just flat out wont start at all. Then I can go back to the car the next day and it will start. Also while driving the car(when it does start) it shows NO symptoms of hesitation/missing etc, so its only upon startup. I had originally feared that the headgasket was leaking when the car would cool down and was flooding the plugs but the plugs are actually covered in gas, not coolant. I’ve done the usual spark related things (cap/rotor/wires/ even tried an ignition coil but returned it when it didn’t make a difference) and cleaned up all the grounds and added one from the chassis to the valve cover. Should I try the other coolant temp sensor that is going back to the ecu?

Does that car have a Crank Angle Sensor? Had the exact same symptoms in another car.

I was actually a bit mistaken… all 4 plugs are not covered in gas. It only appeared that way because I tried cranking it too long that one time when it wasn’t starting. Looking from left to right cyl 2 and cyl 4 are the ones that are the issue. Ive confirmed this a couple of times now

just try a completely different distributor first (very cheap used)

On that note…anyone have a used distributor they don’t mind letting me try?

hahaha your avatar pic is amazing

Just updating this in case anyone finds this searching for a similar problem… it ended up being the headgasket. If I would have just done a leakdown test earlier I probably could have saved myself some needless troubleshooting, but all is good now. I’d also like to say F U to whoever designed the timing cover on the SOHC because getting those rusted bolts out in those tight spots was the worst part of the job!