My front and rear window defrosters don't work on my 2000 land rover. The buttons light up, but the unit does not work. What should I do?

Unlikely to be a fuse blown. Doesn't your Discovery have Daytime Running Lights? If so the right side might be a blown fuse. If the rear lights are on, that mean you have the nighttime lights on.

My mother worked at Land Rover in Solihull for 12 years. :>)

Fuses and relay Land Rover Discovery 2 - Fuse box diagram

fusesdiagram.com https://fusesdiagram.com > land-rover > fuses-and-rela...

Passenger compartment fuse box is located below an to the side of the steering column. Remove cover using a coin or small screwdriver and turning 90 degrees.

They seem to suffer with funky electrics

https://www.google.com/search?q=land+rover+discovery+2+left+front+left+rear+lights+on+all+the+time

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Hi welcome main problems are the abs valves causing the 3 dash lights (search 3 amigos online) a really badly sited compressor can cause air suspension models to fail giving the bags a slow leak the V8 is a solid engine but can have radiator expansion tank and cap failures
the other issue is electrics windows and door looms are problematic

The felt runners that the glass slides in drys out ! get some silicon spary and give the felt and edge of the glass a good spray work the windows up and down and you should see an improvement

No check the brake light switch or brake pedal some of these vehicle have a electronic lock fitted to gear shift

check the rear lighting wire loom from rear of light clusters ,trace the earth wire to the body/chassis connection to ensure a good earth , check for power to the indicater lamp , the bulb holders may be the problem , this is a problem that requires patience as can be hard to trace

There is a resistor pack that controls the fan speed switches. Not sure about the 2000 Disco but on Range rovers of that era it is under the cover below the decker panel.- namely at the rear of the bonnet. Check that it actually is there, then get back to me and I'll post details of how to replace it

blinkers sounds like the flasher unit is not working. It's located under dash. Also check for burnt out bulbs.
Rear defrost, or rear defogger?: Your defogger for the rear window would run off a relay, probably located in the fuse panel of your car. Often, the connections at the rear window get broke or disconnected.
Front defrost: does your heater blower work?

the problem will most likely be in the drivers master window control switch, just replace it and everything should work ok again.

The button is for rear fog lights, The normal park lights should be on regardelass of dash button.

I had the same problem after an interior car wash. I looked all over the car for what might have caused the lights to stay on. On the Subaru Legacy, there is a parking light switch on the top of the steering column. Someone cleaning the steering column accidentally flipped the switch. The engineers that put the switch in a completely different place than the other lights and the button for the flashers did not think things through. Searching around. I did find the button for the front windshield defroster; it was nowhere near the differently shaped button for the rear defroster. The list of bad ergonomic design is a long one. Good car, though, for driving in the snow on hills.