I just installed a new aftermarket system in my blazer and I have alternator whine in my HU's rca outs. The whine is present only when the engine is running and I can hear it through my speakers. I have read previous posts here and elsewhere related to whine but cannot solve the problem.

What I have tried:
I have moved both amp and HU grounds to a few locations without success. My rcas and power wires are on opposite sides of the vehicle. I have tried a different brand of rca and still get the same whine. I have added two 4 gauge cables to my battery and grounded one to the alternator bracket and the other to the frame. Currently my amp is grounded to the rear factory seat bolt on the drivers side. It is a ring terminal held down with a large factory nut. This bolt seems to go through the frame. With the HU grounded to the factory radio wire the whine is a bit noisier than if the HU is grounded to the amp's ground bolt.

I can only eliminate the whine after I take my HU out of the equation. If I plug my creative zen into my amp instead of the HU rcas then the whine is eliminated.

Thank you for reading.

My info:
2001 Blazer LT 4.3L
JVC KD-HDR50 head unit
Kicker ZX550.3 amplifier for front speakers and sub
Kicker amplifier kit with twisted pair rcas and 4 awg gauge cables
Infinity reference speakers in front and back

 

Blazers are famous for alt wine. some say its the blower motor for hvac controls. Try getting a set of RCA's that have a ground woven in. (monster cables makes good ones)

Ground one end to HU and other end to amp.

It seems you are implying that your radio's main ground is to the amp. if they are on opposite ends of the car, thats far to long.

Seat belt bolt for a ground may be an issue too. often they are anodized and don't provide good continuity. sand paint. screw close to chassis. use 2 screws so it will NOT ever move. Or get a big central grounding block to run them all too. Again: sand screw.

 

I was able to try a few things after work today. I have already tried grounding the rcas to the head unit chassis and found it to have no effect on the noise. I tried a radio shack ground loop isolator and it seemed to lessen the whine a bit. It seems like the closer I ground the head unit to the engine compartment the louder the whine. If I ground it to the negative battery terminal the whine is very loud. When grounded back with the amp the whine is noticeably quieter.

Unfortunately I have to work this Saturday so I won't have much time this weekend to experiment with it.

Here are my other ideas
1. Could the alternator be causing excessive noise?
2. Could the head unit be faulty?
3. Add another 4 gauge ground from battery to chassis

 

Try the Ground Loop Isolator on all of the RCA pairs, especially between the amp and the radio. It should deal with the whine. My Sony headunit has an AUX port on it. I can't connect an MP3 player to it directly because every time I plug in the MP3 player to the cigarette lighter I get a loud whine over the speakers that increased in pitch with engine RPM. Same problem with the factory radio with an aux input box. I had to get a GLI, run 2 RCA to headphone plugs (one from the headunit to the GLI and one from the GLI to the MP3 player. Now I can't hear any whine at all (unless I pause the music and turn the volume up to max, and then it is faint). I would also check your ground wires as well and their connection.

 

I tried some more things today. I jumped my oldsmobile to my blazer and ran the oldsmobile's engine. I didn't start the blazer, instead I listened to my stereo with the olds charging my blazer. I didn't pick up any noise from the oldsmobile's charging system. So it might be possible that my blazer's alternator which has 130,000 miles on it might have a bad rectifier bridge.

I also grounded my amp and hu directly to the frame as a test. I cleaned off a spot on the frame to a metal shine and bolted the grounds down. There was no improvement in sound quality.

To recap:
It doesn't matter where I ground the amps or hu.
It doesn't matter if I ground the rca shielding at the hu or amp.
A ground loop isolator does very little if anything for my noise.
Adding large ground wires from battery to frame and block had no effect.

 

Good thinking. Maybe if I get a problem like that, that is the first thing I will try.

If you don't mind me asking, how many miles do alternators normally last on these trucks and how hard are they to replace?

Also if I may make a suggestion (if you are dealing with an amp with the possibility of a larger system in the future and if it isn't too much $$), how about looking at a high output alternator? You might find some good ones on ebay.

 

Today I tried the cd player from my olds in my blazer and got the same whine on the rca outs. So I can safely rule out my hu as being bad.

In response to your questions, I don't know what the average life expectancy of the alternator is. It looks like it would be easy to replace though. The alternator sits on top and seems to have 3 or 4 bolts securing it to the bracket. The belt tensioner isn't hard to access either.

Though high output alternators are badass, in my case it would be extremely overkill for my power needs. My single kicker ZX550.3 powers the whole system and is rated at 550 watts rms. Of those 550 I am only using 350 because I only run a single 4 ohm 10 inch sub and my two front components. Many in this forum run 1000+ watts on the stock alts.

 

I took the blazer to autozone today to get the alternator tested. I explained to the autozone employee that I was specifically looking for AC noise in the system. I don't think he understood what I was talking about. He tested the alternator and it passed so I don't think I will replace it just yet.

 

Just because it past the autozone test does not mean its good! if your going to have them test it, make sure they test it a bunch of times in a row. better yet take the truck to a battery/electrical shop and get a free test of your electrical system under load. lotsa places should do it for free. alt is a piece of cake to change! hope it helps.

 

I achieved a milestone today! Finally some progress to report. I stopped the whine! I just need to figure out how to do it permanently. I began a new test today. I hooked up the head unit directly to the amp. I ran the hu's power, ground, and turn on wires to the amp's screw terminals. I then started the car and had no whine at all!!!

My first theory was that I was finally getting clean power from the amp's power wiring. This however would be proven false as soon as I reconnected my previous ground to the head unit the whine came right back. So after all my tests this is merely a grounding issue. At this point all I can do is laugh at myself.

Now I just need to establish a good ground for my head unit other than at my amp's screw terminal if that's possible! One thing I can't do is use my factory ground wire. The whine is extra noisy when I connect up to the ground in the factory radio harness.

I want to thank everybody for their suggestions so far and I will keep this thread updated with the eventual solution.