I have the standard AM/FM Cassette stereo that came with the car new. My wife uses the car as a daily driver, and I only occasionally use it, so problems go undetected for weeks or months. This time when I drove the car I couldn't pick up any AM stations, none, and I know that there are quite a few in this area because I listen to them in my pick up. FM stations come in just fine. About 4 or 5 months ago we replaced the electric antenna because the motor went out and we just used a manual antenna. My wife can't tell me if she's ever tried to get an AM station since then, so I have no idea if that caused the problem or if the radio itself could be the culprit. Can anyone tell me if an antenna will pick up FM signals without getting AM stations? This seems pretty unlikely, but it would certainly be less expensive than replacing the radio.

/// The same transistors are not used for both AM and FM in some radios. It is possible to get FM but not AM on almost any type of radio. If for instance you were sitting next to a car with a highpower transmitter when it was keyed down you could have the input transistor for AM blown. In addition the wiring for some of these input circuits is small. It can be blown by a large EMF pulse such as lighting.

The ground for both AM and FM is the metal case of the radio. It doesn't matter where it is grounded. If it has power it is grounded.

Unless this is a super expensive radio it is not worth fixing if the problem is in the main radio board. You can open the case on a bench and run the input from the antenna. Clip any capacitors that are between the antenna input and ground. (failed or shorted capacitors on that antenna line would kill AM reception.) Look for burned small wiring at that input.

Except for point to point checking of the input the repairs are beyond the average mechanics training. That KC4IAI on my signature is an amature radio call sign.

I would double check everything you did. If for instance the line from the new antenna was kinked and you pulled it out rather than untwisting it the solid center can puncture the insulation and short to the braid shield. This can be checked with an ohm meter. If you failed to push the Motorola antenna plug all the way into the radio that could give these symptoms.

Thank you for the great informaion. I'll do the preliminary checks and see what I find. And you're right about the cost of a new radio vs repairing the old one.

Yep, it's true. Can't say why, but check the ground at the antenna. FM stations will come in with the antenna ungrounded, but AM won't.

If you really need a radio, they aren't THAT expensive. Most shops have a $50 special.

Thanks Evan. I'll check that out this afternoon. Now that you mention it it makes sense. Replacing the radio would be no problem except that I have a 12 pack CD player going through the radio, so it would be a bit more complicated than just replacing the radio.

Again, many thanks.