Radiator fan issue on a 1998 civic lx, fan does not come on when engine gets hot, nor when a/c system is running. A/C system and fan runs fine and according to the chilton manual, two circuits control the radiator fan, I will also say I know little about auto repair so bear with me.

So far I checked cooling fan relay by applying voltage to hear click and some other test with a multimeter I don't recall the specifics at the moment, Also my friend "shorted"? out the pathway coming from cooling fan switch/temp sensor with a paper clip and the radiator fan turned on, so the radiator fan itself does work as well as the circuit pathway/ relay, to my knowledge.

From this info we decided it may be the coolant temp switch, so I bought a new one and engine fan still never comes on when engine heats up, the engine itself is not necessarily overheating but it may be running hot and i'm sure the engine fan has to come at some point when the engine is hot but still never does, engine temp gauge is around 50% when its hot. We also checked lots of fuses under the hood and under the driver side dash interior, as well as voltage coming to those fuses so its hard to imagine what the problem is. Last night my friend suggested maybe I didn't bleed the cooling system well enough and there could be air trapped right where the cooling fan switch/sensor is I haven't tried to bleed the system again yet. But again, I'm not an expert just trying the DIY approach here maybe you could help. Thanks!

 

One circuit controls the radiator fan, it has its own relay and fuse. Might want to check that again.

 

You will have to get a multimeter and check the circuit.

First make sure power is getting to the relay through fuse 57 and fuse 17
Then check that the engine coolant switch is closing and grounding the circuit.
I'm not really sure what the ECU does with pin A20. I think it can ground override the coolant switch. So maybe you don't need to check that.

If any of those conditions aren't met, you know where your problem is coming from. Check the wiring where you detect a problem first to make sure you don't have any open or shorted wires. If wiring is good, then replace the suspect part.
If all those conditions are met and you made sure the wiring from the relay to your fan is good, then your relay is bad, even if it clicks when you put power to it. Sometimes the connections crack and/or break. It happens.

 

Big Papa Bear, thanks, I will consider all info. We checked alot of fuses with multimeter for continuity and voltage to the fuses already. My friend "shorted" the circuit with a paper clip mimicking the fan switch engaging and the fan turned on, wouldn't that also indicate the relay is working? This observation led me to believe the engine fan temp switch was bad so i replaced it and fan still aint working when engine is hot. Maybe we made a mistake on a step ,it's unlikely though.

 

i have a fail safe thermostat which may have failed in the open position I haven't checked it yet. Is it possible that the engine isn't hot enough for the fan switch to turn on? the temp gauge does say its at about 50% though I'd think that's hot enough but that's just a guess.

I now believe the failsafe thermostats to be a damn pointless hassle if every time it overheats I'm going to have to buy a new thermostat. I'll try to reset it manually before i buy a new one though to save money if possible anyone ever try that?

 

This should be the switch. When it closes, it grounds the wire coming into it to the engine. If you ground that wire to the engine and the fan turns on, your switch is definitely bad; thermostat wouldn't stop the engine from heating up, whether stuck open or closed.

 

I replied with a pick, but it's awaiting moderation now.

But if he shorted the wire from the engine coolant switch to the block and the fan came on, that switch is definitely bad. It's the switch with one wire under the distributor.

You can also check if it closes by measuring the resistance across its nipple and the engine block when the engine is warm. If it's open, your multimeter will not get a resistance reading. Then you know for sure.

 

no, the switch with one wire is for the thermostat reading on the cluster. follow your upper radiator hose to the housing on the engine. see the 2 wire plug and sensor right there? winner.

 

Ah okay, you're right. So there's three sensors related to engine temp...one for the dash, one for the ecu, and one for the radiator fan. Seems pretty redundant on Honda's part when they could all piggyback off the ect sensor. But maybe it's better, since they all don't go out at once if the ect sensor goes.

 

The thermostat and fan switch are on the lower radiator hose. The switch responds to the temperature of coolant leaving the radiator, which is different from that inside the engine. So it can't be combined.

 

well this pic does not look like my 98 civic lx. but the lowest plug on the pic that isnt circled in red looks more like the cooling fan switch/sensor. it looks like this, https://www.1aauto.com/radiator-fan-...FRG5wAodoxcGFA

I've removed it already and purchased a new one, so i know pretty well what it looks like. They even gave me the wrong part initially because i asked for a coolant temp sensor, which does look similar but its not the same thing. These are my DIY mechanic lessons I've learned so far! I think i just learned the correct way of bleeding the air from my coolant system and it takes 10-15 minutes for all the air to be released, and I previously ran the engine with the radiator cap off for about 2 minutes so i know for a fact that's one thing that wrong with my car. I have lots of air in the system I'm sure. I'm not sure that explains why the fan hasn't come on though, we will see soon.

 

This is how I recall it appearing on my 98 civic lx.

 

mk is right. caught me posting at almost 6am lol

 

1 fan switch
1 sensor for gauge cluster
1 sensor for ecu.