So I have this black box underneath my seat that has an on off switch and I was wondering what it is for..it is a 86 nissian d21 4x4

Hi
possibly safety modules for seat belts etc..

thanks

Check for your Voltage reference coming out the PCM. should be pin 86, which is a Black w/Yellow wire. Then check pin 4 on the A/C Compressor Cycling Switch (on the accumulator) to see if you're getting voltage there. Also check the Black w/white ground connection on the left front side of the engine compartment.

Here's a diagram.

Hope this helps!

There is an electrical connector underneath the seat. Verify it is connected. If it is connected, check the fuse (find fuse location underneath fuse box lid). If those two check out, check the voltage at the electrical connector underneath the seat with the heat switch on. Other possibilities include a broken wire inside the seat. If one of the heater wires is broken inside the seat there will be no continuity and the heat will not work.

probably screwed into the gear box at the end of the reverse shift rail. Look for a switch with a wire coming from it at the level of the shift rails or at the bottom of the gear lever at the top of the box.

In a black plastic box on the driver front inner fender under the hood is where you will find the relay and fuses. The black square cubs are relays.

at the back under the boot

It should be on the passenger underneath the dash on the side panel just before the door

i had this problem with my 98 nissian frontier it was 2 things [1] my battery was dead and was not holding charge[2] the belt that runs over the alternator and the radiator fan was really worn i had to replace batter and belt

Hiya...
If you stand at the front of the Equinox's hood that's open, look at the bottom-right corner area behind the headlight area, the battery is 'hidden' underneath the black box-like part that you need to remove clips or screws to lift it up to gain access to the battery cover to reveal the battery sitting onto the battery tray.
It's one of the common thing most people wonder where the battery is located.
The battery is secured into place by a large bolt/black rectangular shaped part onto the battery tray...just unbolt it and you're ready to pull it out.

I have a 2004 CTS. I know there are two fuse boxes underneath the floor carpeting in front of the rear seat. Remove the rear seat bottom cushion and pull the carpet forward and you will see them. Inside the cover identifies what fuse is for what function. Hopefully it is a blown fuse, otherwise my guess would be a short in the wiring some where.