DIY gone bad - From command knob issue to black screen
01-23-2017, 08:30 AM
#1
Newbie
Thread Starter
DIY gone bad - From command knob issue to black screen
Hi All,
I'm more of a lurker than poster, hopefully this can be a helpful post and shine a bit of light on my issue. Great forum.
So the rotation control on my command knob stopped working and after doing some investigation, I discovered that it is quite common for the internal shaft to break after about 4-5 years of use. The knob assembly (part only) from Mercedes Canada is about $450+tax, the full repair would be about $800. You can find them new on eBay for around $200. You can also buy a replacement aluminium shaft, or send it somewhere where they replace the internal shaft for about 60 bucks.
Anyway I came across a great DIY on YouTube to disassemble the knob assembly, remove and repair the existing shaft via 5min epoxy glue. Great, DIY plan in effect. So went through it and got it repaired and went to re-install. The knob assembly cable seemed pinched during removal, so I just snipped the cable to re-splice later during re assy. With the knob out, I started the car and the LCD was still turning on with music playing.
Here comes the rookie mistake: I should have totally cut all power before doing the reconnect. I was real careful to reconnect the proper wires in the correct orientation, 3 solid gray and 1 gray with red stripe. Although I had a plan on using electrical tape as I prepared the wires one by one (there are 4 wires), my exacta knife somehow touch 2 raw wires together causing a small spark. I figured .. sh*t, however I figured maybe the fuse was blown. I finally found the fuse box and looked at fuse #26 (command). To my dismay the fuse #26 is fine.
Wondering: Does the LCD use the command fuse or are there some other fuse I should check ? If all fuses are ok, is it likely that that only the LCD is fried or also the main command system as well ? Music still plays off my iPad connected via the supplied cable in the center console. Wife car is a C300 and I think it uses the same LCD, should I tried the C300 LCD in the GLK to see if that's the issue ?
I'm more of a lurker than poster, hopefully this can be a helpful post and shine a bit of light on my issue. Great forum.
So the rotation control on my command knob stopped working and after doing some investigation, I discovered that it is quite common for the internal shaft to break after about 4-5 years of use. The knob assembly (part only) from Mercedes Canada is about $450+tax, the full repair would be about $800. You can find them new on eBay for around $200. You can also buy a replacement aluminium shaft, or send it somewhere where they replace the internal shaft for about 60 bucks.
Anyway I came across a great DIY on YouTube to disassemble the knob assembly, remove and repair the existing shaft via 5min epoxy glue. Great, DIY plan in effect. So went through it and got it repaired and went to re-install. The knob assembly cable seemed pinched during removal, so I just snipped the cable to re-splice later during re assy. With the knob out, I started the car and the LCD was still turning on with music playing.
Here comes the rookie mistake: I should have totally cut all power before doing the reconnect. I was real careful to reconnect the proper wires in the correct orientation, 3 solid gray and 1 gray with red stripe. Although I had a plan on using electrical tape as I prepared the wires one by one (there are 4 wires), my exacta knife somehow touch 2 raw wires together causing a small spark. I figured .. sh*t, however I figured maybe the fuse was blown. I finally found the fuse box and looked at fuse #26 (command). To my dismay the fuse #26 is fine.
Wondering: Does the LCD use the command fuse or are there some other fuse I should check ? If all fuses are ok, is it likely that that only the LCD is fried or also the main command system as well ? Music still plays off my iPad connected via the supplied cable in the center console. Wife car is a C300 and I think it uses the same LCD, should I tried the C300 LCD in the GLK to see if that's the issue ?
01-24-2017, 09:54 AM
#3
Newbie
Thread Starter
Wife's C300 is a 2011 and my GLK350 is a 2012.
So anyway the command system is working, it's only the LCD screen is black / off. Buttons on command system are lit up and working, radio is working, etc etc.
I checked further into the fuse situation and it seems the fuse number for the LCD screen is 11 so that's what I will check first.
So anyway the command system is working, it's only the LCD screen is black / off. Buttons on command system are lit up and working, radio is working, etc etc.
I checked further into the fuse situation and it seems the fuse number for the LCD screen is 11 so that's what I will check first.
01-24-2017, 02:08 PM
#5
Newbie
Thread Starter
So luckily the fuse #11 was shot and after replacing it, the LCD came back to life.
Turned out that my first attempt at epoxy gluing the shaft was unsuccessful since the rotary function still did not work.
Took it apart, cleaned, prepped and glued again with more reinforcements, using pcs of toothpicks for internal reinforcement and 4 external gussets.
Will report back tomorrow.
Turned out that my first attempt at epoxy gluing the shaft was unsuccessful since the rotary function still did not work.
Took it apart, cleaned, prepped and glued again with more reinforcements, using pcs of toothpicks for internal reinforcement and 4 external gussets.
Will report back tomorrow.
