Radiator Fan wiring problems '83

[Platypus]

Hello,
My name is Charlie and I'm new to the forum and stoked to know it exists. I've already used it many times without signing up. But now I got a bit of a stumper. Here it is:

The radiator fan stopped working. It does not come on at any temp. I pulled the plug from the radiator temp switch(I was told that the fan should go on automatically with the ignition on) and the fan does not run. I switch out the fan for a after market one which I tested by hooking up to the battery, it works. After installing, same situation. I also tried attaching the fan ground direct to the frame, nothing. I thought of replacing the rad temp switch but considering When I pulled the plug to it the fan still didn't go on when It should (despite the plug). I ordered the electrical schematics for this model and will attempt to check for grounding issues all along the signal path, not my idea of a good time. I've only used my ohm-meter/volt-meter once and could use some advice. Also, am I on the right track thinking it couldn't be the rad temp switch? It would be "rad" if that is all it needs. Also, is there a way to replace the motor of the old fan, it's way more heavy duty than the chintzy one I replaced it with. When I tested it ran at first with much labor then petered-out. Thanks any advice you can throw my way.
Charlie

a short bio of my Tercel
'83 Tercel 4wd SR5
name: Platypus(it came with that faded name on it's back bumper)
Color: Camouflage (brown, tan, green, grey)
It's had about 4 owners and has lived most of its life in the hills of northern california between sacramento and Reno. It just passed 250,000 miles. New clutch, brakes, timing belt, carburetor, fuel pump, wires, plugs, distributor, rotor, coil, and some other stuff I'm forgetting. And he kicks ass!

[dlb]

hey charlie. welcome to the forum.

if unplugging the electrical connector from the rad temp switch while the ignition is turned to 'on' does not turn the fan on, and if replacing the fan motor did not work, i would check the fuse and wiring for the rad fan. you already ruled out the ground so perhaps the wire sheath has split somewhere and caused a short.

remember that if the fuse is blown, you must find what caused it to blow in the first place and correct that. otherwise it will just keep blowing fuses.

i think platypus is an awesome name for a tercel. the animal is just as odd yet tough as the car. sounds like the biggest maintenance jobs were recently done so you shouldn't have any major issues for many miles (knock on wood). don't forget to check the front sway bar ends and the bushings there though, and also check the trans and diff oil levels. those are crucial to check on any new-to-you tercel.

[ARCHINSTL]

No help besides what dlb mentioned, but - could this be your car?
https://tercel4wd.com/forums/viewtopic.php?f=8&t=2035
It was owned by a now-lapsed very interesting older guy (younger than moi...) with the handle of kamiphloj. His last posting here was 5 years ago - never left an explanation.
Welcome to the Club!
Tom M.

[Mark]

There should be a fan relay in that plastic box in the engine compartment. I've had one go bad before. You could try removing the relay and temporarily jumping the contacts to see if the fan comes on.

[marlinh]

There should be a matching relay in the fuse box you can swap.

[Platypus]

Thanks yall for the quick responses. I checked what I thought was the radiator fan fuse(in the fuse box under hood, it was a square-ish looking thing) and it passed current. Is this a fuse or a relay? What does the relay look like? Just got the wiring schematics and kinda stoked to dig deeper.
I dont think that is my car (looks like a slightly different camo)

/Users/bbqnervecenter/Desktop/IMG_2466.JPG

[dlb]

can't see your pic, platypus. try uploading it to the server or hosting it on photobucket or whatever and linking to it.

[Petros]

Welcome to the forum!

the relay is round and metal (one of three as I recall), it is different from the fuse. it is labled on the lid of the black box on the left fender.

you have to put "img" and '"/img" in square brackets [...] on each side of the photo address. like this...but you do not have the full address listed or it should show as a picture.

[img]/Users/bbqnervecenter/Desktop/IMG_2466.JPG[/img]

[entrax]

it should be a round relay with 4 pins in the shape of an upside down T. two pins pointing up, two pins parallel horizontally. pin 1 is connected to car's main fuse, pin 2 is connected to rad fan switch, pin 3 to RDI fuse (12v), pin 4 to fan 12v lead.

the relay is a normally closed relay, so the fan should be supplied power from pin 3 to 4 at all times when the car is on, unless pin 2 is grounded (completing the circuit of the relay and opening the switch).

to see if the relay is the culprit, take relay out, put the car to on, no need to start, and you should be able to see 12v from both pins 1 and 3. if you do not see 12v from pin 3, check RDI fuse and wiring between. if you do see 12v at pin 3, connect wire from pin 3 to pin 4. fan should turn on now. if fan does not turn on AND you have verified that pin 3 does have 12v, problem is either the fan or the wiring to the 12v lead of the fan.

if it turns on, great, 12v is being supplied to the fan.

now to ground:
car on (does not need to be running) stick a wire in where the pin 4 goes into, plug relay on, take off plug going into the rad fan switch. measure continuity from the wire connected to pin 4 to chassis ground. 0 = good. infinite = the wiring from pin 4 to the rad fan switch is grounding somewhere along the way when it should not, causing the fan not to come on as relay is energized (pin 1-2 is circuit complete, opening the switch from 3 to 4, cutting off 12v to fan)

good luck! had to deal with this on my old celica. pin 4 to rad fan switch wiring was cut, causing fan to be on all the time. i got lucky that the exposed wiring didn't touch ground, otherwise, no fan all the time!