It will not come on or show the time i have checked the fuse

Hello. Your Mercedes E320 has an electrical 'short' somewhere. Check your cigarette lighter and other 'power point' accessories. That 'short' is not bad enough to 'trip' a circuit breaker or fuse but it will 'drain/discharge the battery in time. Good luck and keep me informed; if you want to.

Not only check the fuse, use a test lite and check fuse circuit for voltage, hot all the time. The ground wire color for radio is black. Other than checking voltage and ground, I doubt I can help?
If the radio theft is activated, my info says, locked, should show on the radio display. After you figure voltage and ground, if locked shows up on the display, may info says you need a scanner to unlock it.

Bad DOG! Break out the checkbook, you may have blown the computer. Need to start there. Not sure if there is reverse polarity diode protection or not. Have it checked. Even at a scrap yard they won't be cheap.

Found these two fuses for hvac. Use a test light, check voltage on fuse circuit, key on. Yes, the ignition switch is involved. Check feed to ignition switch, both show to be red wires, hot all the time. The feed from ignition switch to hvac shows to be orange wire.

second post, reveals , windows. power.
yes, any time any thing electrical fails , check all fuses in both boxes.
ever time. waring, good looking fuse can in fact be bad.
hair line cracks, so we check them with ohmmter (DMM) for 0 ohms.

some cars have windows, circuit breakers, and others fuse links
alldata.com will show the circuit and which fuse it is. every time.
login like we do.

Have you checked B+ power feed for memory to the PCM ? The PCM/ECM - engine computer has a couple of power feeds and one is for the keep alive memory . Looking at a wiring diagram of the powers and grounds would show that . Testing with a volt meter would show if it has power or not . Check PCM B fuse 20 amp located in the under hood fuse box . An don't just look at it ,check for voltage across the fuse . This fuse should be hot at all times .

Sounds like the hot in accy / run position for the fuse is blown ( the symptom is what the radio does when the key is out of the ign ).

Check ( with a meter ) the fuses in the cab fuse panel :# 22 ( this is the pwoer to the radio from teh accessory delay relay ).
The other fuses : #31, #7 and #1

Fuse #31 should be good, this is hot at all times ( keeps the memory and allows the menu to show the clock to function )

Fuse #7 is only hot in the start position ( not sure what this is for to be honest ).

Fuse #1 is hot in Accy & Run positions.

So the total fuse meter check / replace list is #22, #7 and #1

this sounds like a good time to suggest check your fuse panel for blown fuses, there will usually be a detailed diagram showing what fuses do what in your owners manual, and a basic diagram on the fuse panel cover to tell you what fuses to check. I hope this helps.

Check all your fuses - the fuel pump takes its power from a fusible link under the bonnet, check these "big fuses" - Check the fuses under the dashboard too - check them all - a few different fuses could cause similar problem so you'll have to go through them all one at a time.
try this first.

its the same fuse as the feed to the light switch on older vehicles