CreosoteChris
Active Member
Hello – My 93 220CE had an intermittent stereo cut-out problem (aftermarket mid-90s Sony head unit / CD Changer)
- Head unit would apparently lose power, then a few seconds later come back to life, and continue where it left off
- The frequency of the problem was highly variable, sometimes happening every few minutes, but sometimes the unit worked fine for numerous weeks, without the issue recurring
- Problem did not appear to be a physical loose connection, didn’t seem to be related to going over bumps / getting shaken around.
- Electric aerial also stopped working – note that the aerial seemed to be wired to activate with ignition, not with stereo power-up (so it elevated even without the face-plate of the Sony in place.
A couple of weeks ago it stopped altogether, never came back on. I pulled out the head unit Saturday and started investigating with a multimeter. As you’d expect for a car of this age, there’s evidence of amateur wiring-jobs behind the unit, a bit messy but not the worst by a long chalk. I started testing the voltages, and discovered that the red/white cable (should be 12V un-switched, stereo memory “keepalive” signal) was only reading around 1.8V. Tried shorting this with the 12V switched power, and the unit came to life.
Don’t have much confidence (unless someone with suitable insight tells me otherwise) that fixing the signal to the standard red/white cable is likely – so I’m thinking that I need to find 12V unswitched power somewhere else. Obviously I could run a cable from the battery terminal, but that involves going through the firewall, installing an inline fuse-holder etc., and I’d rather avoid further bodge-ups.
Is there another location, preferably dashboard area, to get 12V unswitched power in a ‘93 W124 coupe? Any advice on this (or root-causing the 1.8V signal) appreciated.
Chris
93 220CE red / black leather, 101K, Manchester
- Head unit would apparently lose power, then a few seconds later come back to life, and continue where it left off
- The frequency of the problem was highly variable, sometimes happening every few minutes, but sometimes the unit worked fine for numerous weeks, without the issue recurring
- Problem did not appear to be a physical loose connection, didn’t seem to be related to going over bumps / getting shaken around.
- Electric aerial also stopped working – note that the aerial seemed to be wired to activate with ignition, not with stereo power-up (so it elevated even without the face-plate of the Sony in place.
A couple of weeks ago it stopped altogether, never came back on. I pulled out the head unit Saturday and started investigating with a multimeter. As you’d expect for a car of this age, there’s evidence of amateur wiring-jobs behind the unit, a bit messy but not the worst by a long chalk. I started testing the voltages, and discovered that the red/white cable (should be 12V un-switched, stereo memory “keepalive” signal) was only reading around 1.8V. Tried shorting this with the 12V switched power, and the unit came to life.
Don’t have much confidence (unless someone with suitable insight tells me otherwise) that fixing the signal to the standard red/white cable is likely – so I’m thinking that I need to find 12V unswitched power somewhere else. Obviously I could run a cable from the battery terminal, but that involves going through the firewall, installing an inline fuse-holder etc., and I’d rather avoid further bodge-ups.
Is there another location, preferably dashboard area, to get 12V unswitched power in a ‘93 W124 coupe? Any advice on this (or root-causing the 1.8V signal) appreciated.
Chris
93 220CE red / black leather, 101K, Manchester
