Electric Fan

[mocrotwell]

i have a 1990 geo metro. for some odd reason the radiator fan will come on when the key is turned on and wont go off until the key is turned off. i know this is better than the fan not working at all but i know its not working right and want it fixed. any help would be greatly appreciated.

[Crvett69]

the fan switch sender is the 2 wire sensor next to thermostat housing. unplug it and see if it still comes on when you turn key on, if it doesn't then you just need to replace the sensor. if it still comes on you have something in your wiring goofed up or a stuck relay

[91Caprice9c1]

Correct me if I'm wrong in the case of this 1990 model year.

But I know that in slightly later models, the ECM will turn the radiator fan on if theres an open circuit/fault with the ECT sensor in order to err on the side of safety.

If that's the case than this method of diagnosis wont tell you much.

I suggest getting your hands on a wiring diagram and a DVOM.

-MechanicMatt

[Crvett69]

the sensor is always a open circuit until it reaches about 205 degrees and turns the fan on. would still just turn key on and unplug it and see if it goes off. also make sure no one has just jumped the sensor to make it run always. also if you have a car with AC make sure its the radiator fan thats coming on and not the AC one

[91Caprice9c1]

If it's carbed I could see it being a bi-metal switch such as you are suggesting. I was under the impression that '90 cars were fuel injected, in which case it would have a thermosistor, right?

Hell just pull the plug and get back to us, tell us whether it's tbi or carbureted and we can go from there.

-MechanicMatt

[Woodie83]

All Metros are fuel injected. It's a switch that runs the fan and nothing else. There's also a thermistor for the temperature gauge and a seperate thermistor that reports to the computer.

[91Caprice9c1]

Thanks guys for clearing that up for me.

Whats the word Mocro?

-MechanicMatt

[mocrotwell]

ok, i have changed the fan switch, checked the coolant temp sensor, it seems to be working good, dont know where the fan relay is located so cant check it, also doing all this checking i found a wire that has been ran from the fuse box and tied into the blue wire on the fan switch, if i unplug it the fan goes off and will not come back on... i dont understand it

[GM Line Rat]

1. The fuse and relay box that contains your cooling fan relay is under the hood, on the Drivers side fender well (#9 In this pic)
Underhood Fuse and Relay box

Originally Posted by mocrotwell

also doing all this checking i found a wire that has been ran from the fuse box and tied into the blue wire on the fan switch, if i unplug it the fan goes off and will not come back on... i dont understand it

This tells me that someone has bypassed the Cooling Fan Relay and wired the fan "Hot at all times" when the ignition switch is on. Look at the pic below, the Lt Blue (Light Blue) wire feeds directly from the Cooling fan relay terminal B7 to the Cooling fan + Terminal......Buy a new cooling fan relay, completly remove the wire that they "Rigged up" to bypass the relay from the Blue Cooling fan wire, tape up any open wire connections where they installed the bypass wire, then install your new relay in the underhood relay center. Due to the fact that it's Winter now, You'll have to run the car parked / Idle until it reaches a temp where the cooling fan will kick on at it's designated temp to properly test and see if the new relay is engaging the fan circut properly?.....Unless you live in a failry warm temp state in March?

[mocrotwell]

my car does not have a number 9 relay, there is not even a spot for anything to be there, the other relay that is there is for the blower motor inside the car, up until a couple weeks ago the fan was cycling just like it was supposed too, now for some odd reason its not working right

[GM Line Rat]

Your Blower motor Does Not operate off a relay, it recieves it's power from either 1 of the resistor value terminals in the blower motor resistor pack or full power (HI Speed) directly from the fan speed switch inside the car. Better go back and look around/under or behind the under hood fuse/relay box for the Cooling fan control relay......The relay your pointing out as the blower relay is the HORN Relay, and is clipped onto the front of the Fuse relay box. The schematic wiring diagram and pic of the relay/fuse box I posted above points this out and shows a "Cooling Fan Relay" in both of them. The relay will have a rubber cover over it and look just like the Horn Relay. BTW, Where was/Is the power wire that they rigged up to power the cooling fan connected at? (On Both Ends).


Underhood (Drivers Side) fuse and Relay Box

[mocrotwell]

the photo you provided looks exactly like whats in my car except there is only one relay clipped onto the front of the relay box. the one i have does have a rubber cover over it and when i removed it my inside blower motor didnt work, thats what made me think that that relay worked the blower motor. the wire that is hooked into the fan switch comes from inside under the dash its tapped into the fuse labeled "heater".\

Thanks,
Monti