I have a 1988 740 Sedan. The left rear speaker emits no sound. I have swapped speakers and determined that the problem is not the speaker. Is there a simple diagnostic check to determine if the problem lies with the radio or if there is a broken wire. I am considering replacing the radio with a CD player, but I don't want to do this if the problem is in the wiring.

Thanks,

Mike

Hi,

I don't know if your car is fitted with factory amp. On the assumption that it is not, you can do a check as I did with my radio when i had problem with my speakers (turn out to be my amp). This is what I did. I removed that radio from the dash and then at the back of the radio there is a connector. First I identified the power and ground wires and made a mental note. I took a cheap tweeter (don't want to burn my expensive speakers) and tested with both wires from the tweeter into the connectors at various connections with the music on. If you have the balance/fade knob try it out first with the balance/fade knob in the middle (i.e by allowing all speakers getting the sound). If you get sound from all 4 pairs of speaker wires (some have additional 2 pairs of speaker wires for on dash tweeters - like mine), then there is a connection break somewhere else. Hope this helps. i don't know any other way to determine if your radio is at fault.

Has someone else have any other ideas?

velan@hotmail.com

Volvo 940GLE, 1991, B234F, Kuala Lumpur, Malaysia.

/// Have some one turn the radio on while you listen at the speaker. If you hear a pop when the power is turned on there is nothing wrong with the speaker, the wire to the speaker or the output of the amplifier.

It is possible for the fader control to be open and you might (repeat might) be able to spray it with control cleaner. If it is cracked on one side spray will not help.

If you have a high power separate amp the shielded wire to the amp may have contact, solder, or break problems.

Without having a block diagram or schematic it is hard to just guess.

Repost if you do not find the trouble. You did check the plug from the final radio/amp to the speaker for corrosion or pull out, right? A powered circuit continuity tester, battery and bulb, can be used to check the wire and speaker from the rear of the radio. Disconnect the radio and just scratch the tester across the two speaker wires, briefly, very, very, briefly. You should hear a sound as the weak DC current causes the speaker to sound.

DO NOT USE A LARGE BULB TESTER AND DO NOT LEAVE IT CONNECTED TO THE SPEAKER WIRES. I have used just an AA cell but I have a lot of practice.