Radio noise

[reb]

As my '94 T100 has aged, the AM radio reception has deteriorated. Engine noise drowns it out when I am in an area with weak signals. New ignition wires did not help. I figure there are some filters in the electrical system. Anyone know where they might be hidden?

[2tacomas]

You may want to think about replacing your speakers (if they are still original stock equipment). I had a similiar problem in my 1988 Toyota P/U, I went ahead and installed a whole new sound system- it solved the problem, sounded a whole lot better (I put more powerful speakers in it), was fairly easy to do myself, and it didn't cost nearly as much as I thought it would. If you plan on keeping that truck for a while longer, I would highly recommend it. Also, make sure your antenna is tight- sometimes they can work themselves loose and cause poor reception.

[reb]

Thanks, 2tacomas.

I will check the antenna. Since FM radio works satisfactorily, I am sure the speakers are not the cause of the noise. I will consider replacing them when the AM radio works correctly.

[Billy_The_kid29]

do you get engine noise on fm as well? if so you have a bad ground

[GregoryM]

Can you be more specific re. "engine noise"? Usually RFI (radio frequency interference) takes one of two forms. A high pitched whine is caused by the alternator/charging system. A rhythmic ticking is usually from the igniton system. Depending on the source you can track down the cause. A capacitor will usually quiet a noisy alternator. An electrical choke on the power lead to the radio can also help. An electronics store can help you select a proper capacity and show you where to connect it. If the igniton is the source, you can check the usual components: plug wires, dist. cap, rotor, resistor plugs, etc. Sometimes you can shield the antenna lead with aluminum foil and that has helped me in the past. You don't mention the condition of your antenna but, I will assume it is in good condition. Hope this helps. Good luck.

[reb]

Thanx for the suggestions.
I haven't figured out whether it is alternator or ignition caused. It isn't a whine and it isn't a rhythmic ticking. I suspect the alternator circuit, but I was hoping to locate the factory filters and check them out before digging deeper. Its possible that the antenna connections are corroded, too. The cable looks ok; so I expect the shielding to be ok. At times like this I curse the crowded wiring behind the dash. It is a b*@$# to work on.

[GregoryM]

The factory uses capacitors in the charging circuit. You should be able to locate them with a schematic diagram. If the antenna is in poor condition, electrically, it sure could be your problem.

[reb]

I have the factory manual, with the schematics. The schematic does not give the physical location of the filter cap. I didn't see it the first time I looked for it. I guess I'm too lazy. I'll just have to break down and search more carefully. It should be close to the igniter &/or the ignition coil.

[GregoryM]

Actually the factory wiring diagram DOES show where to look. It breaks down your vehicle into a grid. You must look within the designated "square" but it at least gives you a starting point.

[reb]

I spent my career working with electronic schematics in the avionics industry, but the automotive industry does things differently. I will have to study the manual to figure it out. So far the only reference I can find to component location points to areas in the schematic diagram to find things.

[walterycrigler]

I have the rythmic ticking problem in my 98 Camry LE. Has rear window integrated antennae -works fine. Ticking also occurs when (factory) cd is playing. How is this a signal bleeding into antennae problem? I dont understand - but would love to fix it. It seems to be getting worse.

[reb]

If the ticking occurs with a CD player the antenna is out of the picture. It sounds to me like you have what we in the electronics business call "conducted interference." The noise is probably coming into your amplifier via the power line. There might also be a way for radiated noise to be carried into the amplifier, too. What are the characteristics of the noise? How fast is the ticking? Does it increase with engine speed? If the noise is getting worse, I would guess that the circuitry (possibly in your radio/cd player) that filters out the noise is degrading with age. I figure that is what has happened with my truck.

[dna59]

You might wanna check your grounds.