View Full Version : Radio interference
04-17-2008, 10:17:15 AM
I just installed my radio back into my car. Wired in an amp with new 6x9's (also have door and dash speakers) and now I have radio interference. I can hear my electric fuel pump as well as my electric water pump. The battery ground goes to the front of the block and then I took another ground from the back of the block into the driver's side firewall and attached it to the underside dash and attached the radio ground to there.
Where should I start first. Can you buy a noise filter that will take care of it or is it going to be more complicated than that. Should I isolate all of the grounds on the car. I'm not sure what direction to go. I've wired alot of radios in my day, but, never had a problem with noise interference.
Any help would be appreciated.
04-17-2008, 10:34:21 AM
Where is the amp? Sometimes if you have the 12v (to the amp) too close, or ontop of speaker wire you will get feedback. They do sell a noise suppressor that will kill that humming niose you are getting. I used to be able to hear my wipers through the radio......VERY ANNOYING during rain.
04-17-2008, 11:18:01 AM
The fuel pump is the culprit. Electric motors are very noisy RF generators, and a good radio can pick that RF up like it is designed to. You probably want to try to put filter capacitors on the fuel pump motor like GM did on the heater motors.
04-17-2008, 12:28:30 PM
Grounds are more than likely the culprit as well. Is your amp getting the signal from RCA cables, or through speaker wires? If RCA's, disconnect them from the amp and see if you're still getting the interference. If not, then the noise is coming through the RCA's themselves. Get a ground loop isolator for the RCA's. If it's still coming in, then the noise is either through the power or through the air. Try moving the amp further away from the noise sources or try a better ground. Most noise is caused by what's caused by a ground differential; the radio might be seeing 12.6V and the amp is seeing 12.4V type of thing. Try also running a ground wire between the radio and the amp to help correct this. Hope it helps.
04-17-2008, 06:31:06 PM
The amp is mounted in the trunk and the fuel pump is mounted directly below it underneath the car. The amp gets its signal through RCAs. They both have seperate grounds. Well, come to think of it. One is grounded to the rear subframe and the amp is grounded through the body. Technically, it's the same ground. (This might be a good excuse for subframe connectors. :) ) The electric water pump and fans gets their ground from the radiator support via relay. DCC control.
Thanks for the direction guys. I'll try to find some time to get it straightened out and I'll let you know what the "fix" was.
04-17-2008, 07:21:36 PM
the noise is from your power source. Run a inline 12v filter, ground loop isolators on the RCA [raidoshack], and make a nice big short ground.
A ground should be as big or bigger then the +.
Why most run all new wire to isolate the stereo system.
also if the pump is real close its magnetic field it creates could bleed through the air and metal. Make a buffer or block.
To keep a big dual 12in box on my TV once, it took two pieces of aluminum flashing with some plywood in the middle to block the magnetic field that turns my TV screen funny colors.
Had some problems in my 3rd gen, to get it crystal clear I used some amplfyied headphones that I could plug into the RCAs to fiddle till it was clear with nothing playing, I just listend for power feed noise or static.
04-17-2008, 10:57:06 PM
Thanks for some more good advice. I did use all new wire for this install and bought the large size cable. The ground is already short and I just used leftover wire for the + cable as the ground. Should the inline 12v filter be mounted at the battery where the + cable is or should I mount it next to the amp or does it even make a difference. I'll visit Radio Shack and see about the isolators. I'll get this problem whipped now. Plenty of ideas.
04-17-2008, 11:01:13 PM
well its the raido you need a filter on the 12v if you don't have one, hook it up near the raido, the amp don't need one, they have them built in. Sure it says moseft power somewhere if its newish......
04-17-2008, 11:08:22 PM
Ahhhh, I see. That saved me a lot of hassle. That's for sure. :confused: How about the loop isolators? Does it matter which end they will go on or should I just read the instructions. ;)
04-17-2008, 11:17:34 PM
they hook inline with the RCA cable and are marked in and out.
04-17-2008, 11:28:36 PM
So, just read the directions....:p
Thanks for all of your help. A trip to Radio Shack will be happenin' tomorrow. I plan on driving the car to pick up my six year old son from school and some tunes would be great. :cool:
04-18-2008, 04:05:00 AM
also did you seperate the power and rca cables when running the wires to the back? if they are ran next to each other down one side of the car that can cause noise aswell.
04-18-2008, 03:23:15 PM
Good insulated wire shouldn't though.
I sort of break all the rules on that but have good results.
I use good 3 wire extension cord wire for my amp.
I use all 3 wire for the + from battery to amp.
The amp ground has 2 small section, 6 wires.....
If you wanna go crazy I know likes of folks who use welding cable wire.
Most of that stuff they sell for cars is cheap made junk. Extension cord and welding cable wire is made to much higher standards as it carries allot more juice.
05-02-2008, 04:34:15 AM
how did things work out???
05-03-2008, 01:09:50 PM
I bought the ground loop isolators at Radio Shack and installed them inline at the amp in the trunk. The noise went away but it killed all of my bass coming from the 6x9s. I tried plugging the loop isolator in both directions and had the same result. I don't get alot of time to play with the car since it isn't stored at my house. (yet)
As far as the power wire and the RCA wires, they are run down opposite sides of the car. The only thing that is run next to the power wire is the rear mount antenna wire.
I've tracked the problem down to my electric fans and the electric water pump. They are both run off of my DC controller. I'm going to try moving the ground from the controller to a more direct ground. (straight to the battery)
I'll let everyone know how that went when I get a chance to work on it.
05-03-2008, 06:41:22 PM
Well if you can get ride of the noise you don't need the loops, but they help when ya got noise ya can't get ride of.........
06-26-2008, 09:31:53 AM
Did ya ever get anywhere???
It may be the AMP, I just dug out an old amp to put a decent raido in the wagon and it wines like a bit..............
Obviously the mofest power supply in the amp is not functioning right or just ins't that good. I used the same brand of everything in the wagon, hooked up all the same way, but that old 600watt amp isn't filtering alt noise right.
I am gonna go buy a noise filter for the power supply.
06-26-2008, 02:19:50 PM
Went to radio shack and they donít sell them anymore, I got a 12v noise filter off a radio I could use but its fused for 3amps, amp has 2 20amp fuses.
Ebay is no help, ground loops thingy isnít my problems here, the radio puts out no noise, the noise is in the amp.
06-26-2008, 08:39:38 PM
Had a brain fart and got mine all fixed, no noise filter of any kind were needed.
I use the same brand of radio on purpose, I got a pioneer DEH-P4000 in the 3rd gen, one I installed in the wagon is a DEH-P2900, The 2900 is newer, does MP3 n such but has less dewtailed auido options.
Then I membered both radios have RCA outs, and sub woofer RCA outs.
The Sub RCA give out clear clean sound, the regular ones didn't/don't.
So I hook up my regular speakers to just the front output wires.
Turn on the hi pas filter so noting but highs come out of them.
Then hooked my 6x9 box bridged on my 600watt amp via the sub RCA outs.
Good clean sound now. Since the reg speakers are all just highs, they can go way up to match the sub box and not sound like crap not being on the amp, while the 6x9s in the box can thumb as hard as I want since the sub channel has all it own adjustments.
Got the 2900 on Ebay as a refurb with a 1yr warranty for $80
Come with a remote too.
Get a DEH or other raido with sub outs, and dump the ground loops.
Only run bass though the amp.