quick question about my stereo. So i wired a new head unit and an amp and a sub, all that stuff works great (thanks to rover chris's wiring diagram and cutting into the speakers at the amp harness). I tried replacing the 6.5"s on the back gate with a 3-way 6.5" and everything works great, i ran it off channel three of my amp and when the truck isnt RUNNING it's got great sound, but when the truck is running, theres a pretty loud whine coming from just that one speaker.
What could cause switched interference like that?
Just to try and answer any setup questions that may come first, im running 20ft rca's from the back of the head unit (preamp rear) into the amp, theres no L/R on the amp, only one input for each channel, so the rca's are plugged into channel 3 and 4's inputs. From the back of the amp, im running reg speaker wire over to the 3-way on the door. Im not bridging or anything. do you think i have a bad connection at the head unit? Idk what would cause the interference only when the truck is on.

Best

Turf

 

Just to rule it out and to prove my theory, remove your fan belt, start the truck, is the noise gone?
Yes?
RFI from the alternator, you need a noise cancelling resister capacitor thingy thing.

 

I'll check it out tomorow. I did buy the cheapest RCA's i could find. Maybe they're not well enough insulated
thanks pal

 

So i didnt check the alternator because it seemed to be a bit of effort to get the fan belt off. What i did check was all my grounds (good) and what i learned is that the interference also goes away when the subwoofer pre-amps are unplugged from the back of the head unit. Since those wires have NOTHING to do with the noise coming out of the other RCA cables on the other amp channel, im inclined to believe you're right phil. I think i might have cheap cables that aren't shielded well enough and arent playing very nicely with the other RCA cables. If i have time tomorrow, i'll grab some new ones and see what happens. What a pain in the ***. Stupid stereo

 

spike, i havent popped the belt yet (mainly because i dont know how and this isnt the computer with my rave on it) but i do know the whine increases with engine RPM, if it's an alternator shielding issue, what do i need to shield? Here's what i posted in the A/V section:

New rca's didnt help, went back to the original, here's my new ground, brought straight from the back of the head unit harness, joined to solid wire and fixed to the firewall


Here's what i learned today. The noise IS affected by engine RPM, i.e. throttle up-->whine up.
the noise DOESNT matter what channels are plugged in, when i run the 6.5 off of channel 3 it whines, when i run it off channel 4 it whines.
When i only plug in one RCA to the back of the amp for channels 3&4 (for the channel running the speaker) i get no sound, when i plug in the one that doesn't have the speaker run off of it, i get noise.
Is there anything else diagnostic wise i can do to this thing? I'm pretty well stumped. I'll re-check the amp ground tomorrow, but it's done similarly to the head unit ground.
Is this something i could take to an indy shop and pay them to fix? Or would i waste all my money on them trying to find the problem?

 

To remove the belt you put a socket on the nut in the middle of the belt tensioner and push down, you may need to use a cheater bar for leverage.
Once loose slide the belt off, there should be a diagram under the hood of the belt routing, otherwise it is in the tech section.
Once the belt is off start the engine, the noise will be gone.
I have no idea how to fix it.
I had some noise with one of my bad alternators from AutoZone.

 

A good idea to practice changing belt, which is a fairly common service task. Other options would be to remove the two smaller wires from back of alternator, or fuse 14 inside the truck, which provides volts to make alternator "excite". The flying lead wire on the back of the alternator (push on connector) is the drive to the tachometer. But fooling around on back of alternator means main battery should be unplugged. Then you drop your presets in swanky new radio.... so the belt remove may be the best path.

The attached RAVE page shows a suppression capacitor external to the alternator - perhaps your is knocked loose or missing.

 

I had that exact thing happen when I replaced my head unit. You can fix it with an in line noise filter. I got mine at Pep Boys for less than $10 (Metra #CK-NSFL2). You solder it into the + power supply (red wire) and then ground the black to the chassis. That's it, no noise.

 

If that's my solution I'm going to kiss you. Thanks man.

 

please keep an eye on that wire - especially where its crimped into any connections - solid core wiring (along with wiring nuts!) is not meant for applications where vibration exists.... like your car.

if you have an extra couple minutes, i would redo that with some stranded wire.