HVAC goes nuts when bass is turned up

Has anyone had this issue? I just replaced my head unit, and now when I turn the radio up all the way (full bass) the HVAC unit goes nuts....turning on and off, etc. I am just wondering if the unit itself is going bad, or if anyone else has had this issue.

Its fine when the volume is down, but when its cranked the thing goes haywire....flashing different characters, turning the defrost on and off.....please just tell me that the HVAC might be bad. Is there a way to reset these things or should I just buy a new one?

When you replaced the head, is that all you changed?

Do you have a subwoofer?

How fresh is your battery?

What is voltage reading when you see problems?

AA wrote:

When you replaced the head, is that all you changed?

Do you have a subwoofer?

How fresh is your battery?

What is voltage reading when you see problems?

I changed the head unit, added speakers and an amp. No sub. Battery is possibly a year old. I am not so sure its a voltage issue (will check that) but I am able to make the HVAC go nuts if I simply "hit" the side of the unit itself. So I am leaning toward the vibration causing the issue. I ordered a new HVAC (used) to see if this fixes the issue. If not, Ill return it. Im thinking something is loose in the unit itself since I can reproduce the issue by banging the side of it.

We'll see when I get the new one, but thanks for the response. I was just actually curious if anyone else has the same with added vibration.

I have a subwoofer that shakes everything in the car, but it does not bother the HVAC system. However, I did see the HVAC behave erratically once when my alternator started putting out 17+ volts!

It does sound like a vibration issue, based on your "smack" test. I wonder if during the installation maybe you rubbed part of the HVAC wiring, breaking through some of the insulation. The head unit chassis may be contacting and shorting one of the wires to ground, causing the chaotic behavior.

Sounds like the HVAC unit may be bad. I can't see out of my rear view mirror when the bass is up, but never had an issue with the HVAC unit....

I'd verify that the connection plug at the back of the HVAC unit is all the way in and not loose. Also check the insulation on the wires for a rub through.

Might also need to disassemble the HVAC head unit and flean the little carbon pads behind the buttons, and check the circuit board for cold and intermittent joints.

Albertj

Had the HVAC unit ever exhibited any odd behavior before installing the head unit? If not, there is a very good chance this is an external issue (wires, connections, etc) related to your installation procedure. If the HVAC unit was bad internally, or needed cleaning, chances are you would've experienced some problems before the install, as the vibrations experienced in everyday driving far outweigh anything you're going to see with a new head, amp and door speakers.

Remove the head and check wires, insulation, and connectors for any kind of chafing, shorting, or disconnection.

wires appear to be ok. The sound vibration is certainly more excessive than regular driving vibrations. It never acted up in the past. Once the new HVAC is here Ill see if it does the same thing. If so, Ill add a stiffning cap to the setup to see if that helps

Thanks for all the suggestions!

There are a few solder points inside the head unit known to go bad. I wouldn't be surprised if the extra vibration might do in a couple that were questionable (but unnoticed) before.

I second to double check the connector on the rear of the HVAC head.

Well, it was the unit! I took the old one out and shook the shit out of it...lol. I hooked it back into the car and it didn't turn on at all!!

So the new unit arrived today, installed it and no issues at all. Works great with the radio up all the way. I suspect a loose diode or resister in the old hvac unit itself. Too funny