Rear Defroster - 2002 Nissan Altima

Relay maybe . free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. year , make , model an engine size . Under system click Body & accessories ,then under subsystem click on rear window defogger . Click the search button then the blue link .Looking at the diagram you will see three fuse's , a relay ,lighting control module , defroster switch . The switch is a input to the lighting control module , the lighting control module will supply a ground to the control side of the rear window defroster relay ,energizing the relay sending B+ power to the defroster grid.

check fuse... check wiring to the switch... check wiring to the rear window...

none, if it lights up then power is going to the defroster. the problem is that you have a small tear in the defroster grid

check for current at the back electrodes that connect to the heating element for rear defroster.
check that the light goes on the button area for it to verify if any power is going to the circuit.
check for a fuse that powers the rear defroster.
Also, check that the relay for it is clicking or provides power to the rear defoster.

Good luck for this repair.

It could be a bad rear defroster control switch or relay, it could be a loose or damaged connector somewhere in the defroster circuit, or it could be a damaged or defective defroster grid on your rear window. The easiest way to check to see if you have a circuit problem or a grid problem is to check for voltage at the connectors to the defroster grid at the rear window area. These connectors may even be located inside the trunk just below the rear window. If there is power there, then the circuits are OK and the rear window will most likely have to be replaced to fix it. If there is no power there, then the circuits must be traced to locate the cause of the failure...Most likely a burned-up switch and/or connector.

The main cause for the rear window not working is a disconnected wire at either side of the defroster grid. You can see where the body harness connects to the rear glass.

The second most liekly cause are broken defroster grid wires.

I would suggest to you to obtain a 12 volt DC testlamp, and check for voltage as follows, at the rear defroster.

Hook the clamp of the testlamp up to a known good ground. The back door latch 'hoop' is great. Next, turn on the rear defroster, and place the point of the tip on the extreme side of the back window, on the grid. Does it the tester light up bright? If not, try the other side.

The light, moving across the grid, should get noticeably dimmer, if the grid is functioning properly. The light will go out when you encounter a broken grid wire..

rear defrosters are an apllied film of semi metalic strips and if you get you windows tinted often the tint man accidentally nicks these strips cuasing the defroster to malfuction check for breaks in the srips

check your fuses first,with a test light,then if you have power there take your test light and turn on the rear defroster and probe the wires that connect to the rear defroster in the rear window.if you have power there it is a faulty defroster in the glass

change the switch, check any junkyards.