What a fun little trip that turned out to be.
Last weekend two of us took a road trip from North NJ to Northern Virginia in my (ahem) trusty '96 N/A 850. We got stuck in traffic at the bottom of nj, and before the car seriously overheated and managed to hurt itself, I got it pulled over in a Turnpike rest stop. I carry tools with me whenever I road trip, so I had enough stuff with me to figure out what was going on, and get us back on the road again. I had a test light in the kit, and when I noticed the engine cooling fan not working, I thought it might have burned out, or a fuse popped, or a relay, or something, so I looked around, I unplugged the power and ground wires from the fan, and using aligator clip leads, I powered it right from the battery, and it spun immediately.
Next I tried testing the power and ground circuits, and the ground side was still good, but I was getting no power to the fan. I carry my Hanes manual with me in the kit with the wiring diagrams in it, so I looked for a fuse and everything. I unplugged and tested the relay and ECT sensor, and they were both still working properly, so I basically butchered the fan by cutting the plug that goes into the relay off, and sending a fused wire directly from the battery to the fan. It worked perfectly for the entire remainder of the trip.
Once I got home, I was really able to dig into the car and ohm tested the power wire and figured out the wire was dead because the fusible link in it had popped. The rest of the fan circuit was working perfectly, but the fan died because it wasn't being fed power.
I ran a new fused power wire from the positive battery terminal right to the fan, ran it as neatly as I could, and just left the rest of the system alone because it was all working well. I had neve had a fusible link pop on mein the middle of use, but it bit me this time.
The car is home, repaired, and safe again, but it definitely wasn't fun working on it in the rest stop while my girlfriend chewed through some concrete blocks.
Has anyone else ever run into a problem with this wire before, because it seemed odd to me. Every other acessory on the car was working properly, but the fan was just dead no matter what I did to it ( I tried switching on the A/C before I dug into things) ?

 

Resurrecting an old thread. I believe I have this same issue.

My radiator fan will not turn on and has caused overheating in drive-thru's.

It will not turn on from the A/C switch
My fan will turn on when jumped from the battery

My Coolant Temp Sensor is brand new
My Cooling Fan Relay is brand new
My thermostat is brand new

The wiring to the relay from the battery has power

I am not skilled enough to know how to test my ground wires to the relay (the high and low ground switch)

I am so confused! Is my ECU faulty?

Months ago I changed my sun-visor since it would not stay up anymore and would always fall down on any small bump.

It had wires coming to the light for the mirror. So I cut the wires and rewired them (i swear to God it was wired correctly) with crimp splicing connections. and ever since than my lights do not work inside my car. If I try to turn on the light it beeps at me like the ignition key beep.

Maybe this caused the whole issue of wiring in the first place???

I am so confused and not an expert with cars. I am an advanced beginner at best.

please help

 

Test 30 for a constant 12volt.

Put ground to "1 in" and you should hear the relay click and fan turns on.
Put ground to "2 in" and you should hear the relay click and fan turns on.

If you don't hear the relay click and you have 12 volt at 30, the fan relay is bad.

 

That's how I test the relay! thank you. I wish the relay was the issue, I bought a brand new one and the fan still wont function.

 

I used a code reader and I have P0117 and p0102

The fan works, the relay works.

I unplugged only the center plug of the connector and grounded the prongs to the engine chasis one prong at a time. I heard a LOUD click from the relay but no powering on of the fan.

I believe the issue is the wiring from the ECT connection going to the relay. Or am i wrong about this hypothesis?

 

How do you know the fan works?

 

i know this because i can power on the fan from the battery.


Bypass relay
1)I connect a wire from the battery positive to the pin on the green wire (not the relay) and then
2)connecting the fan ground (black wire found strapped to the fan shroud not the ground leading away from the fan but the one coming from the fan) grounding on the engine block
once it is ground the fan turns on.

but i figured out my issue! My ground lead is bad. The fans ground that leads away from the fan is not grounded.

i bypassed the ground and the fan kicks on when the temperature rises

Bypass ground:
1) get alligator clip and connect to the cars chassis on a good connecting spot.
2) take the other end of the alligator clip and connect to the ground (black cable on top of fan body/shroud) and connect to the part going down into the wiring harness NOT the part going to the fan itself
3)Turn on car and let it heat up, if your ground was bad the fan should kick on when the engine temp rises

To fix it just got off the old ground and insulate the open cable and then reground anywhere on the cars chassis with a self tapping screw