Engine noise through the radio.

[185K89SHO]

High pitch noise through the radio, changes tones with changes in rpm. You can even hear it with the volume turned all the way down, but not off.
This system has been in three cars, and the SHO is the only one that has this problem. It a Kenwood reciever (10 yrs old),an EQ, and a couple of amps. I checked all wiring to the amps and reciever, replaced patch cords to the amps in the trunks, tried installing a "ground loop isolator", nothing helps.
I'm using the wiring to the factory radio to power the reciever and EQ. (ign,batt,grd)and have a seperate battery cable to the trunk for the amps. Any idea what is causing this? Any guide lines on where to go from here would be greatly appriciated. I am about ready to buy a new head unit and eliminate the EQ and the FM CD modulator and have it all built in.
John
89 SHO

 

[RickieFrat]

John .... Check ALL your grounds. Also try to use a different grond for the head unit and EQ. If that doen't work ..... lower the gain on the amp to the interior speakers.

 

[185K89SHO]

All grounds (reciever, EQ. amps) measure 0.2 ohms between the unit and the neg. battery cable. I did not try to seperate the EQ and the reciever. I'll have to try that. The gains are only about 1/3 to 1/2 up now. I hate to turn them back even more!
Should the amps be externally grounded? (case ground). My amps are mounted to a board instead of being screwed to metal. I'm wondering if I should attach a ground wire on 1 mounting screw on each amp and and run that to a body ground (sheet metal. Or maybe attach a ground wire to the body of the reciever and EQ? Thanks for your help.
John
89 SHO

 

[LOUDSHO92]

Your alternator might be going bad. If it is not it may be smaller then the previous cars. A cap solved the problem in my car. You might want to try it. It will only help.

 

[ericwick19]

if you have the RCA's between you HU to your AMP routed on the same side of the vehicle as the power wire for your AMP, you WILL get engine noise though your speakers.....

 

[185K89SHO]

Finally, problem solved. One of my preouts that wasn't being used was comming in contact with the metal brace behind the dash. It used to have a plastic cap on it, but it has disappeared somewhere. Wrapped everything up with electrical tape and the noise is gone. Thanks to everyone for your help and suggestions.
John
89 SHO