Multiple problems that an experience nissan enthusis could solve in seconds

[87stanza]

1987 Nissan Stanza GXE Automatic

I need help with these 4 items:

Problem 1 - Which "Radiator Fan Switch" on the radiator(upper or lower) do I replace the new with?

**Trouble shooting for problem 1**
My fans are not working properly. I discovered this when I developed a small leak in radiator and realized that my fans were not coming on. I spent all day researching why they were not coming on and found that the problem was the "radiator fan switch" after some website suggested that turning on the a/c would make the fans run then it was the radiator fan switch.

So I ordered one but mine has an "upper" and "lower". I don't know which one to replace. The salesperson at AutoZone suggested I refill the radiator, turn on the a/c and see how long the fans would run.

Problem 2 - What is the relay switch diagram in the engine compartment on the passenger side.

**Trouble shooting problem 2**
Well now the fans are coming on but when I turn on the a/c, I hear the compressor kick in, then I hear a relay switch click and then the fans turn off. The fans do not turn back on at all until I turn the a/c off and then they come back on. Repeated this several times and everytime the same thing happens.

Any suggestions; I believe it is the "a/c relay switch" but my engine compartment relay bracket has no cover to let me know which relay is which so I don't know which one is the a/c relay or radiator fan relay.

I can not locate the a/c relay switch and can not find out which one it is in the auto repair manuals either.

Problem 3 - Also, how can you tell if a relay switch has gone bad since it is encased inside a seal cap.

**Trouble shooting problem 3**
Just do not know how to tell

Problem 4 - Sensor identification

**Trouble shooting problem 4**
There is a sensor(about 3" in height) located on the exhaust manifold where it creates a Y. The sensor has a wire(I believe green) built into it that is also about 3" long with a female connector. The location would be like this: Front of car; radiator; radiator fan; then the sensor directly in the center of the "Y" on the exhaust manifold below the spark plug wires.

What is that sensor? I kindda pull the wire out by accident while unplugging and replugging connections to ensure proper connections. The car still runs but rough now.

Thanks and any help would be great. I kindda at the last straw before I take it to the dealership.

[{LK} Mario]

well i cant really help you with all of your problems but i can help you with the last one. The wire you unplugged goes into your oxygen sensor, the reason you car is now running rough is because without the sensor, the computer is becoming confused about how much gas/air should be in the combustion mixture, so yeah that was a bad idea, Your service engin light didnt come on when it was unplugged? you should be able to simply plug it back in and it should work fine. and these are not nissan, almost every newer car has them, mine has 2 and both are bad
lol. but that should help if not just post again. sry i cant help you with your other problems!