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1993 400 SEL
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206 Posts
Discussion Starter #1
Just had my Bose Amp rebuilt last spring, Works and sounds amazing for old Tech, I have the original 3 peace Becker 1432 and CD player in the trunk that works flawless and a new Antenna by Hirschmann , all is well...BUT ? been having a battery drain for the last couple months , So i did a test and found it was my Bose Amp when i Unplugged the harness from it my Volt check dropped to normal ,and then i plugged it back in and it now has no more Voltage drop when off ?? Is the Bose amp Switched/Triggered ? thinking if so maybe a bad micro switch ? any thoughts ? I will check it again in a few days to see if that drain comes back .pic shown at .83 V and then it dropped to .13V and now stable ! damn thing lol
 

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1993 400 SEL
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206 Posts
Discussion Starter #5
The Bose Amp does have a internal switch small relay , It gets triggered on the same circuit as the power antenna , and that was working fine so i knew the Head unit was sending it's signal ok, So i noticed even after i had the Bose rebuilt that when power was turned on it had a very small noise when turned on , It stopped doing that , So after doing the circuit draw test i was all over my Fan blower motor resister that had gave me trouble and replaced last year and fixed that issue, Then i found a couple 980 Becker CD players , both had Eject gear failure that i repaired and installed, The gear problem will also Drain your battery after trying to eject as the car is turned off , Started pulling fuses and the rear trunk fuse number 16 Stereo was the one .. But then had to figure out by unplugging the CD player and that was not it,,,so then the Bose , The relay switch inside must be worn and must have stuck on some how, after i re-plugged it now is working fine, 1 year warranty if it does it again. Cheap fix !
 

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Registered
1994 S500 Coupe
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581 Posts
The Bose Amp does have a internal switch small relay , It gets triggered on the same circuit as the power antenna , and that was working fine so i knew the Head unit was sending it's signal ok, So i noticed even after i had the Bose rebuilt that when power was turned on it had a very small noise when turned on , It stopped doing that , So after doing the circuit draw test i was all over my Fan blower motor resister that had gave me trouble and replaced last year and fixed that issue, Then i found a couple 980 Becker CD players , both had Eject gear failure that i repaired and installed, The gear problem will also Drain your battery after trying to eject as the car is turned off , Started pulling fuses and the rear trunk fuse number 16 Stereo was the one .. But then had to figure out by unplugging the CD player and that was not it,,,so then the Bose , The relay switch inside must be worn and must have stuck on some how, after i re-plugged it now is working fine, 1 year warranty if it does it again. Cheap fix !
Thanks for the explanation! And the future owner who needs this will thank you too! :p
 

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600SEL
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1,083 Posts
The trigger for Bose amp is not the same as for power antenna. It is not coming from the head unit but from the tuner/amplifier in the trunk, the single wire with fast-on connector.
 

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Registered
1993 400 SEL
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206 Posts
Discussion Starter #8
The trigger for Bose amp is not the same as for power antenna. It is not coming from the head unit but from the tuner/amplifier in the trunk, the single wire with fast-on connector.
The Head Unit Triggers the Tuner that triggers the Power Antenna, So kinda the same source, Without the Head unit powered up nothing will work ..Also while checking voltage draw remove both trunk compartment lights while testing with trunk open, Also remove Becker CD cartridge magazine from CD unit or it will draw power to reset each time battery is reconnected including Volt meter in line for testing ..
 
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