Re: Radio Test 190E

Rick, sounds a a bit like a bad fader but, when you disconnected the fader you said only the passenger dash speaker quit. Does that mean you had still had sound on another speaker in the system with the fader pulled???

If you had your meter set to Amps when you measured the door speaker wires, it is likely you would blow a fuse. (Use 3v AC setting and check for voltage.). But it also indicates you have a connection back to the amp. Was it the amp fuse that blew?

Trace the signal (3v AC meter will work OK). Play some music, preferably a tape with even volume. Set fader to middle. There are many configurations in MB models and I do not have a wiring diagram for yours so this is just a guess. Console mounted fader on all my cars are the same though. Here is how you can test fader signals:

- Most have Left and Right coming out of the radio head unit (or out of a trunk mounted tuner) into the fader (measure input pins S1 and S2 on fader)

- The S2 (left) input splits into E2 (frt/Left) and A2 (rear/left) (measure at those pins) You can check fader by watching voltage as you move fader knob. Voltage will be erratic due to music but you should note a relative change.

- The S1 (right) input splits into E1 (frt/Right) and A1 (rear/Right) (measure at those pins)

- If all is OK at fader, note the wire colors at E2, A2, E1,A1, and measure signals at Amplifier input.

If all that checks out, trace the amp output signals (they naturally will be a high voltage with the same music and fader setting). Usually the front dash and front door speakers run off the same amplifier output, so having a right dash speaker work but not the right front door work is a clue. If yours is wired that way, you need to trace the wires carefully and check for bad filter components in the front (caps or coils) in the front speakers.

Also note that some of these cars have a trunk mounted tuner/preamp and smaller two channel amps mounted behind the seats. That changes the test procedure a bit.

Scott D

Both rear speakers in my '92 190E have suddenly stopped working, also > the drivers side dash speaker recently cut off. I have speakers in both > front doors that have never worked since I've had the car. Occasionally > there would be slight,faint murmers of sound from the door. > I pulled the radio(stock cassette) fuse o.k, wires seem o.k after > cleaning connections o.k ...but there are 3 prongs on the radio back > without a plug. Checked door speakers, out of car and they work!... > blew a fuse checking for current to drivers door speaker, disconnected > fader (which killed the only sound from passenger dash speaker) and > cleaned prongs. Could all this be a bad amplifier (in trunk, > above passenger side rear wheel well) Benz price 285.oo ( but they > cannot check it off the car, minimum 2 hours labor) Any ideas,... how > to check amp or find prolem > (drivers dash sound comes and goes like a loose wire) Thanks > guys.........Rick >
Reply to
Scott D
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The best is to upgrade this ugly sound system with a new one as I did, and use the speaker placement of a MB did. Just a though.

Reply to
W126

Thanks for the reply, I think I'm over my head here. All sound, is off... from all speakers except, the right dash speaker which sounds like a 10.oo clock radio, flat hand harsh. Unplugging the fader left me with no sound at all! I sanded the prongs and replugged it, no improvement at all. The fuse that blew was to the power windows (right front and left rear) I was thinking I would find a loose wire or corroded contact. I've got a small multi-meter, and circuit tester....I was using the multi-meter to test for current in the door speaker plug when the fuse blew. what is the vacant 3 prongs, without a plug for?..... on the back of the radio? I found the trunk mounted amplifier it has, as I recall a single rectangular 10 pin connector cap plug. Benz wants 2 hours labor to tell if its good.

Reply to
r parris

Sounds like you are getting close. Good chance that it is a bad fader they do go out often - subject to coffee and the like. You should either try testing it with your multi meter as I described or switch it out with a known good one. The fader is simply a variable resistor which splits the input signals (e.g. pin S1) into a front signal (e.g. pin E1) and a rear signal (pin A1). Set your meter to your lowest AC voltage setting, clip one lead to ground and touch the other leads to pins looking for voltage as descibed in earlier post. The pins are marked (tiny letters) on the fader itself.

You can also check the fader by pulling it and testing the resistance between pins S1-E1 and then pins S1-A1. Then pins S2-E2 and then pins S2-A2. If it is good, resistance will change smoothly as you rotate the fader.

If the fader is good, you will need to get someone on this forum to give you color codes of the amplifier output wires to test with your meter. Then you'll know for sure if it is the amp.

Scott D

Reply to
Scott D

Rick,

I've got a fader from a 190. Let me know if you need it.

Reuven

Reply to
Reuven

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