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2008 ML 320 CDI
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Discussion Starter · #1 ·
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.
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1993 SL500, 1998 SL500 Pano Top, 2005 ML270Cdi.
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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
 

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2008 ML 320 CDI
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Discussion Starter · #3 ·
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
 

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1993 SL500, 1998 SL500 Pano Top, 2005 ML270Cdi.
Joined
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975 Posts
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?
 

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2008 ML 320 CDI
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Discussion Starter · #5 ·
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.
 

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1993 SL500, 1998 SL500 Pano Top, 2005 ML270Cdi.
Joined
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975 Posts
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.
 

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Discussion Starter · #7 ·
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
 

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Discussion Starter · #8 ·
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.
 

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Discussion Starter · #10 ·
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