[Glen]

2008 ML 320CDI. Factory radio - just picks up static (AM & FM). Station can be heard under the static on some frequencies. All other features work fine. Reset of the unit did nothing. I believe the antenna amp is not functioning. I’ve checked the red lead / red connector but only see 0.5V at the amplifier with radio on. So, before I replace the amp, is it getting the correct voltage? Fuse diagram shows fuse #20 for this amplifier. I’ve checked this fuse and it’s ok and had power. Looking for help, guidance and corrections if I’ve done anything wrong. Not an electronics guy so “dumbed down” answers welcome.
Thank you in advance.

 

[RedLiner]

HI Glen, if you are not into electronics it's probably not an option for you to open and try to effect repairs.
They are not too expensive and I've just found some on eBay.ca new and used Here

 

[Glen]

HI Glen, if you are not into electronics it's probably not an option for you to open and try to effect repairs.
They are not too expensive and I've just found some on eBay.ca new and used Here

Thank you. I wasn’t planning on a repair - just replace if needed. My concern is if the amp is getting sufficient power to work (0.5V). If not, a replacement is a waste of money. I’m really looking to know what voltage I should be seeing.
Cheers

 

[RedLiner]

Thank you. I wasn’t planning on a repair - just replace if needed. My concern is if the amp is getting sufficient power to work (0.5V). If not, a replacement is a waste of money. I’m really looking to know what voltage I should be seeing.
Cheers

Glen you say the the fuse for the ant. amp. has power, what is the voltage at the fuse?
If it is the supply to the amp, then there should be 12v. at one of the amp terminals, is this correct?

 

[Glen]

Glen you say the the fuse for the ant. amp. has power, what is the voltage at the fuse?
If it is the supply to the amp, then there should be 12v. at one of the amp terminals, is this correct?

I just went and double checked. There is one very thin red wire/coupling into the amp as well as the 2leads to the glass antenna and the co-ax plugin. At the red power (?) lead I measured 0.5V with the radio on. Regardless, I’m concerned it’s supposed to be 12V. I’m thinking of running a 12V wire to the antenna amp to see if it’s any better.

 

[RedLiner]

I just went and double checked. There is one very thin red wire/coupling into the amp as well as the 2leads to the glass antenna and the co-ax plugin. At the red power (?) lead I measured 0.5V with the radio on. Regardless, I’m concerned it’s supposed to be 12V. I’m thinking of running a 12V wire to the antenna amp to see if it’s any better.

I've been trying to find a circuit diagram of the comand system in the W164 without success, so I don't know what the input voltage is for the amplifier.
Before you take that step it might be prudent to ask here first.

 

[Glen]

I've been trying to find a circuit diagram of the comand system in the W164 without success, so I don't know what the input voltage is for the amplifier.
Before you take that step it might be prudent to ask here first.

I think first step I’ll get another amp off eBay. At this point the amp is sitting on the bench and the radio reception is unchanged driving around. So clearly the amp isn’t doing anything. If the new one doesn’t fix things I’ll try 12V to the old box. Interestingly if I touch a length of wire to the end of the co-ax I can significantly improve the signal so it seems I just need an antenna that connects to the radio. I’ll give an update once the new amp arrives
Many thanks

 

[Glen]

I think first step I’ll get another amp off eBay. At this point the amp is sitting on the bench and the radio reception is unchanged driving around. So clearly the amp isn’t doing anything. If the new one doesn’t fix things I’ll try 12V to the old box. Interestingly if I touch a length of wire to the end of the co-ax I can significantly improve the signal so it seems I just need an antenna that connects to the radio. I’ll give an update once the new amp arrives
Many thanks

So, finally the “new” antenna amplifier arrived - purchased off EBay. Installed it and no difference to the reception problem at all.
So I re-installed the original and ran a 12V supply to it (rather than the 0.5 V it was getting. Reception was instantly perfect - pulled in all the stations as it should. So, it would seem the power supply is the issue. I can’t locate a wiring diagram and am crap at troubleshooting electrical issues so for the moment will get it 12v from somewhere.

 

[BoatWaco]

I cannot vouch for these folks, but searching online for wiring diagrams did yield this site: Mercedes Wiring Diagram – Free Resources – MB Medic

 

[Glen]

I cannot vouch for these folks, but searching online for wiring diagrams did yield this site: Mercedes Wiring Diagram – Free Resources – MB Medic

Thanks, will see what’s there. I did just find one diagram posted in a forum for the radio system. It was a very pixelated scan but seemed to show the power lead for the antenna amp coming from the roof antenna.

 

[BoatWaco]

Try here too StarFinder
Go into the W164 model, Web ETM with StarFinder and then into the section 82