4200NEX Audio Fluctuating

Hello, I will preface this with "I am a car audio novice" so, please forgive me for the lack of specific details. I recently had a Pioneer 4200NEX installed by a reputable shop in town. I have been dealing with some issues that I am trying to independently research as I can tell that the shop is getting frustrated with me bringing the vehicle back. What I have is the 4200NEX, in a 2006 Toy 4Runner which has the JBL Synthesis upgraded soundsystem. My understanding is that this system has a stock amplifier connected to the speakers. I also paid to have a new "module" installed that I believe controls the interface between the steering wheel buttons (volume and track advance) and the head unit. I am having a problem where, on any input source, the volume of the unit will fluctuate without me pressing any buttons. Some times, the volume will go way up and then go all the way down for a while, then come back up. Other times, I will have to turn the HU up to volume 20 just to hear the music well. Under normal operation, I have never taken it up to vol 20...that would be way too loud. Other times, it works just fine. The installer has replaced the HU already and is now indicating that they may have to do an amplifier bypass. Could the issue be in the module? The installer claims "no" because when the HU adjusts it own volume, there is no audible beep like there is when you use the steering wheel buttons. Thanks for your help. I'd like to educate myself a little before I go back. Josh

As I read through your post, I reached the same conclusion as your installer. I say bypass the factory amp. Your headunit will only have four speaker outputs, so it may not play through all your speakers. As long as impedance is not an issue, you may be able to run the front door woofers/tweeters on the front outputs, and the rear door woofers/tweeters on the rear ouputs. Other speakers (dash speakers, etc.) may not play, but this is probably the easiest/best option. You can always upgrade your speakers and add amplifiers later if you want.My ex once told me I have a perfect face for radio.

Thank you for your reply @geepherder. I appreciate it. Any idea as to what the cause of the issue is? Do newer HUs not play well with older factory amps? I bought the car with an older double DIN JVC and never had the volume problem. Im curious as to whether I could try a different (less expensive/less featured) HU and avoid the amp bypass. I go the NEX for carplay but, Im not that sold on it. Thanks, again. Josh

I think the issue with amp integration is overdriving the inputs of the factory amp since the new unit puts out a higher level signal. Sometimes integration harnesses use the RCA outputs instead of the speaker outputs of the new headunits. With that volume issue, I'd say the damage to the factory amp is probably already done. I think trying another unit would just be throwing away money.My ex once told me I have a perfect face for radio.

Thanks for your input. I appreciate it. The installer recommended sending it to an amp repair shop to see what, if anything could be wrong with it.

No point in doing that, just bypass the amp and call it a day.double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

The JBL synthesis system is a 10 speaker set-up. Would the 4200 NEX run all 10 speakers including the Sub? I would seriously regret going down the path of this upgrade if I end up decreasing the overall sound output of my vehicle and paying upwards of $700 for it.

Do you know what interface was used? Metra makes one for amplified systems http://www.metraonline.com/part/AX-TYAMP1 and I've installed them in the past without any issues.Tell me again about your 5,000 watt amp you got for $99.00

I am also confused about this.