I hope somebody can shed some light on this because I am truly baffled 
…
First off my car is a 90 DA with a 2nd gen B16A swap, it has NO A/C.
So I’ve been having some overheating problems when stuck in traffic, and determined that my rad fan was never turning on. I replaced the ECT switch (on the thermostat housing) with this one 
This did not solve my problem.
I’ve been going nuts testing wires for continuity and volts and here are my findings.
- When the fan is wired directly to the battery (yel/black to +, yel/green to -) it works
- With Ign on, when the fan is wired using the factory + wire (yellow/black) and ground to battery it works
- When engine heats up, the ECT switch reads ~0 Ohms, it has continuity, when cold there is no continuity… Everything seems fine up to here right…Now the weird stuff…
- Now I’m bypassing the factory wiring ECT switch wiring, leaving the yellow/black + wire connected… when one side of the ECT switch is grounded, and the other side is connected to the - (black) wire of the rad fan, with the engine hot, IGN on and with there being continuity between the two terminals of the ECT switch (and thus we are grounded), the fan DOES NOT work. Reversing the ECT switch wires does nothing.
So what the hell is going on here? Basically all is well until I try to use the ECT switch to ground the rad fan…
#25 40amp block fuse? ( i think?) That caused my overheating problems. It is a big green block fuse that is screwed in the driver kick panel fuse box. I had a loose connection on it. Caused my AC to turn off and radiator fan to shut off.
I had all sorts of other stuff going on and that fixed it ALL.
Its the green one at the top with 2 copper wing looking mounts on it…mine literally was loose AND had loose mounting wing parts (dont know technical term for those lol)…bought 4 dollar fuse, washered up the loose screw. No issues since.
Thanks for the insight, mine however was fully tight (was able to squeeze about 1/8 turn) and tested with a multimeter and the fuse is fine. And FYI that’s the ‘heater’ fuse
Yup, and oddly enough, it caused my AC, Radio and Fans to not come on…shrugs It was recommended on g2ic.com I check and replace it when I posted up a “Bizarre electrical issue” post of my own this year…just sayin, even if it tested OK you may want to replace it and or check the other fuses as well…
Should be the relay then. Since you bypass it and the switch, and fan comes on. Switch reads continuity hot, so its good. Should be relay.
Put power and ground to the coil side of it and test for continuity of the control side
I had the same problem 8 mouths ago… I change the switch 5 times I even put a buddy club switch…
I went to the dealer and got a switch no more problems…
also I dont see if you tested the realy it is be hind the left side headlight…
Correct me if I’m wrong. But with no ac there is no relay. I currently tapped into the ground wire of the fan and ran a switch inside to ground it, therefore im using the factory ‘power’ wire… The problem is with the ect grounding the fan
Rad fan also uses a relay and aC fan uses a separate relay. Pull that sucker out and test it
Check out the schematic… http://www.sfu.ca/~dew5/RADFAN.jpg
My setup is the far left!
Yes, I have looked at the schematic already.
Pull the relay and test it
Also, be sure to test it for continuity. Don’t just hear the “click” and assume it’s good. The contacts could be bad
