I recently replaced an aftermarket stereo with another aftermarket and when I did, I lost quality in the FM radio signal. When I change to usb or aux it sounds fine.

There was an "Antenna switch box" by Pioneer(cwm4331) behind the radio that the antenna plugged into it. It was a box and had a wire and plug into another plug that I'm guessing is an antenna amplifier and then had the antenna plug for the stereo. I replaced this whole unit and it improved but I'm still receiving static on all stations.

I wired the antenna straight to the stereo just to see and it sounded terrible.

This is driving me crazy. I can't figure it out. Any suggestions?

 

Back in the day on the old cars, we used to wire a condenser to the coil to suppress static in the radios. I am not sure how you could do that on the electronic cars we have today, but I am guessing your problem is similar. Have your tried to run an additional wire from the radio chassis to the body? Might help. Also make sure all wire attachments to the speakers are secure and tight if you haven't already.

 

Plug yet a 3rd head unit into your car and see how it sounds.

It's very possible the head-unit itself is ( at least part of ) the problem. I have plugged/unplugged many radios into the same system one after the other and have witnessed the better - or poorer - quality reception of some decks over others.

It sounds like you had a Pioneer "FM modulated" harness in there. They were used to run an add on component ( CD Changer ) thru an adjustable FM radio channel. Removing it was a good idea simply because your taking 2 breaks in the connection out of the equation in your hunt for better reception !

P.S. Sometimes this helps: Unscrew and then re-install the Antenna mast. Use a wire brush to clean the antenna's fender mounting stud while it's apart.

 

@jtsk, I'll have to look into that. I'm pretty sure all the speaker connections are good because when I play my iPod on it, it has perfect quality through each speaker equally.

@John in Rl, that sounds about right about the CD thing. When I bought the car there was the stock head unit and a CD changer installed behind the back seat. I removed all of that though. But when I replaced the modulator with a new one, the quality in the radio DID improve a little bit. It sounds horrible when I wire it straight to the deck though. It's weird because it didn't do it until this new unit. My last head unit was a cheap one I got from Walmart.

I haven't ruled out that it may just be the head unit itself. I have a Kenwood and haven't heard many bad things about them yet but you never know. I'll try the antenna thing soon and check back.

 

Did you ever figure this problem out? I'm having the same exact issue and its driving me nuts

 

+1 for a good ground:

good ground from battery to engine, engine to body, and radio to body

 

so should i ground the radio to the body instead of the old ac delco radio harness?

 

I never was able to fix the radio static as I got caught up in everything else. I usually just plug my phone in and listen to Pandora stations. But something that I thought of later down the road was the tinting. The tinting I have on my car isn't the "premium" stuff they say messes with GPS and radios and maybe the new stereo had interference with it.

Other than that I'm not really sure unless it was the stereo itself because all the wiring was the same as the old aftermarket stereo and that one worked fine.

 

It's a ground issue more than likely. Run a new wire directly to body metal. If you're increasing the length, be sure to increase the gauge so current can flow out.

 

The radio gets its ground from a splice, you find where that splice gets its ground and clean up the area with a wire brush or steel wool. Chances are its the dash frame, probablyunder the drivers side huish panel around where the steering column screws into the car and a dash bracket aswell. Also the dash frame grounds itself where it mounts under the hush panels, two 10mm bolts I believe hold it in place. You could unscrew that and the ones on top, and move the dash a bit so you can get to that area to clean it. The factory grounds worked well for many years, chances are that the grounds are f-ed and if you dont find the root cause of the issue, it will just stat to affect other things.