2008 Kia Optima: Low-pitched "hair dryer" sound on AM band

if it's in ACC then it has to be something non-engine related. Heater blower fan, perhaps?

nate

Start pulling fuses until you find the circuit the noise source is on.

Maybe, or possibly a choke. If you hear the noise with the engine off and the ignition in accessory mode, you know that it has nothing to do with the engine or engine controls, but with one of the accessory devices. Find the noise source and either fix it or install some filtering at the source.

--scott

Electrical noise from the car can get into the radio in two ways, radiated noise and noise riding on the power lead.

Noise that is radiated by the car and picked up by the antenna is much harder to get rid of. It is almost impossible to filter it out of the antenna system. The normal method is to eliminate it as close to the source as possible. Are you using noise-suppression spark plugs? You should be. Even so, a bad plug can create bad ignition noise, though it sounds more like static than a hair dryer. A bad alternator can make lots of electrical noise. Make sure you have a good alternator and that filter on it is good.

Noise from the electric wiring that gets into the radio from the power lead is easier to stop. Most radios have a good filter in their power supply section. A component of that filter may be bad. Or, if it is a cheap radio, the filter may just not be good enough. Radio Shack used to sell a power lead filter that you put in the lead bringing power to the radio.

Diagnostics. Hold a portable AM radio next to your car when the car is running. Note the noise. Do the same with a few other cars. Is the noise worse near YOUR car? If so, you are radiating noise and need to fix that. If that portable does not note excess noise near your car, than the noise is likely getting into your car radio on the power lead.

If the sound is there on AM but not FM, then unfortunately that means its not coming in through the radio amplifier electronics, but is being picked up by the antenna itself. AM modulation is susceptible to this and the car's ignition or charging system is obviously not well shielded You can try a series inductor on the radio power feed with a parallel capacitor to ground after the inductor (an LC filter circuit) but I give it minimal odds of success.

I wouldn't go that far- if the engine or transmission or body controller module is powered (and the body controller often is powered in ACC since it controls things like the radio, power windows, etc.) then it could still be harmonics of the processor or bus clock or logic circuits. Just like a badly shielded home PC.

_____________________ I do apologize - I neglected one piece of info: I had the service dept manager listen to AM on several 2008 optimas identical to mine with the same exact stereo, and they all had the same sound - at the same points on the AM band. FM reception flawless on all of them.

Will some sort of capacitor/noise suppresion still help in my case?

thanks,

-CC

Not surprising.

Depends on what is causing the problem. Start pulling fuses.

--scott

_________________ So, with the car in ACC, I pulled the following fuses, one at a time:

- Clock

- Airbag sens

- DRL

- Several "spares"

- Taillights

- Fuel pump

- ABS

- Power seat

- sunroof

etc.

Notice a pattern here? Most of those fuses govern items that run full- time, including sensors. Nothing eleminated the low-speed hair dryer noise in the background of certain AM stations.

I didn't bother pulling fuses for things like trunk lights or interior lighting, as they are on-demand items, meaning they usually come on only when you are entering or exiting the cabin or operating the decklid.

All nuts that transfer current between the battery, the alternator, and the fuse boxes, as well as any ground terminals(that I could access!) to firewall or engine block have been checked tight and retightened by me.

? ? ?

-CC

Did you find the fuse for the heater blower fan? that's still my best guess.

nate

__________________ I did pull that, but again, that is an "on-demand" item - on only when the driver selects it from the dashboard.

-CC

Most of the cars that I've driven don't actually have an "off" position for the fan... e.g. my 944 does have a "O" position on the knob, but the fan is still running at low speed.

If you play with the fan speed while the radio is on AM, does the pitch of the noise change?

do you have an old head unit that is known to work well laying around? Maybe the radio just sucks. Most radio mfgrs. don't spend a lot of time sweating the details on the AM section because honestly, most people never listen to it save for the odd sporting event that's not broadcast on FM. (and now, that may be irrelevant if you have satellite radio)

If you end up replacing the HU consider getting one with "HD radio" (not really an accurate description but whatever.) AM on digital sounds really, really good. I bought one for my truck and unfortunately have grown to really like it, to the point where I'm considering getting another for the 944. Unfortunately the model that I bought (JVC KD-AHD39) has been discontinued, and the replacement does not have preset buttons, which means I'm stuck looking at closeout retailers etc (unless someone can recommend a similar current product from another mfgr?)

nate

Sounds like the antenna outer coax is not grounded. Alligator clip ground the antenna and coax at the antenna and see.

und the antenna and

_________________________ The antenna in this car is the in-glass method at the rear window. Should I alligator it at that end or close behind the radio(that will require dismantling the dash of which I'm not too inclined?

-CC

the antenna and

That's a POS antenna and likely you have interference from the engine computer itself.

the antenna and

Ground it at the window end. Its also possible that the antenna coax is not firmly seated in the radio. Or one of the inline plugs has come loose.

ground the antenna and

s not firmly seated

______________________

Paul, Steve, if any of those were the case then my FM reception would be equally in the outhouse(!) When I talk about picking FM, in stereo, up from Newark NJ to Hartford CT, I MEAN from Newark NJ to Hartford, CT!

I live about equidistant between those two. On the AM side I get in clearly WFAN 660, WSTC 1400 and WNLK 1350(both within 10 miles of me),

1010 WINS, WCBS 880 news, and a couple others. If any of you are familiar with WABC 77AM NY, they are supposedly a clear channel certified station but with their TX site in freakin' New Jersey instead of ontop of the ESB or some other high spot in Manhattan, they are lost in the ether. It is WABC and 1130 NEW AM that both have this hairdryer sound in the background, probably because they are relatively weak from my location in southern Fairfield Co.

On my wife's car, they are just softer than the other stations, but NO background noise whatsoever. To hear them in that car I just need to raise the volume a few values. In my car, it's like driving next to a hairstylist's chair while a customer's hair is being dried!

-CC

p ground the antenna and

is not firmly seated

do you get the same noise on other AM radios in the area, how about a portable near your car?

many am stations are not xmitting iboc which xmits wideband hash, if there is a 790 or 750 in your area xmitting iboc, that could cause the noise on 770 and it has nothing to do with your car.

check with another car or a portable radio

Mark

the antenna and

firmly seated

AM is amp. modulated, FM is freq. You can have partial antenna loss and have terrible hissing AM without noticing any loss on FM until the FM turns off. The options are: bad radio rf noise be generated somewhere in the car bad antenna bad coax

I agree with the other replies: Find a portable radio and stick it in the car and see if it makes the same noise. Plug another antenna of some sort into the radio. A long piece of wire will do.

lip ground the antenna and

ax is not firmly seated

_____________________ Mark, reread the paragraph beginning with "On my WIFE'S CAR..."

Paul, as far as trying different antennae, good idea! BUT - Today's dashboards are another tale as far as getting into them or behind them. This is not the '80s or earlier where members of the Philips family held everything together in plain sight. ;)

-CC

-CC