Amp wiring and voltage drop problems HELP!

[MMast 10+ year member]

Earlier tonight I was trying to help a friend with an install problem. Here's the preface: he currently has a 2002 Pontiac Grand Am with monsoon, in which he has 2 Power Acoustik 10's and a Power Acoustik Amplifier. The source is a LOC from the stock head unit, when measuring the LOC the DMM measured no AC voltage from the RCA. When I measured the voltage the amp was receiving it initially measured 12 volts with the ignition turned to the off position, but when it was turned to the ACC or ON position it dropped to around 7v. I'm slightly puzzled as to what may be causing this, any help would be greatly appreciated.

Thanks!

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[Paulspikey 10+ year member]

The voltage is coming from the battery. But you should hopefully be getting at least 2 volts from the preouts. 7 volts is really low. I would buy a new battery. Try it with the car running see if your voltage goes up to 12.5- 13.

 

[MMast 10+ year member]

I measured the voltage at the battery and it reads around 12.5v. Also should the LOC be tapped into the factory amplifier in the trunk or would tapping it at the Head unit before going to the amplifier be the better solution?

 

[maylar 10+ year member]

I don't understand the 12V/7V part - where are you measuring? Power to the amp should come directly from the battery and not change with ignition switch.

What is the LOC powered from?

Ideally you want to tap the LOC from the HU before the factory amp, but you need to know what the signal levels are... some systems use speaker levels some have low level signals. I dunno what a monsoon has.

 

[MMast 10+ year member]

I don't understand the 12V/7V part - where are you measuring? Power to the amp should come directly from the battery and not change with ignition switch.
Measuring from the positive and ground terminals on the amp and not changing anything other than the position of the key the voltage drops from 12v when the car is off to 7v when you turn the car on.

What is the LOC powered from?

The LOC is being powered from the 12v from the harness at the factory HU.

Ideally you want to tap the LOC from the HU before the factory amp, but you need to know what the signal levels are... some systems use speaker levels some have low level signals. I dunno what a monsoon has.

I figured the HU would probably be sending low level to the amplifier so I could probably just tap the LOC at the factory amplifier (located in the trunk), but also if it is sending high level signals to the amplifier then there would not be much different between the high level signal at the HU and the high level signal in the trunk?

Any suggestions?

 

[maylar 10+ year member]

Measuring from the positive and ground terminals on the amp and not changing anything other than the position of the key the voltage drops from 12v when the car is off to 7v when you turn the car on.

Then something is very wrong. Assuming you have typical wiring, battery -> fuse -> amp, you should have 12V with the engine off and 13-14 with it running. Nothing should change with the key (other than start). Do you have a fuse in the power wire?

I figured the HU would probably be sending low level to the amplifier so I could probably just tap the LOC at the factory amplifier (located in the trunk), but also if it is sending high level signals to the amplifier then there would not be much different between the high level signal at the HU and the high level signal in the trunk?

You should get that clarified.. maybe someone here knows the monsoon system. If it's high level from HU to factory amp you're better off tapping into that because the full range signal is before the amp. Factory amps filter the sound to the different speakers. If you have to tap into the amp's outputs then do it from the biggest speakers, they will have the most bass signal. Even so, some factory amps will filter the sub bass out and that's what you're looking to get.

 

[quackhead 10+ year member]

Any suggestions?

Double check the fuse near the battery, check voltage on both sides of it..check grounds, check the voltage at the battery posts when turning from off to acc on the ignition. If you are seeing the same drop at the battery posts, I would have the battery checked, possibly replaced.

I am with maylar on the LOC..I don't have experience with the system to recommend the optimum LOC placement

 

[quackhead 10+ year member]

Monsoon System Pinouts - GrandAmGT.com Forum

 

[MMast 10+ year member]

Thanks for all the help guys, I really appreciate it. I will keep it all in mind when I get a chance to take a look at the car again.

 

[maylar 10+ year member]

Monsoon System Pinouts - GrandAmGT.com Forum

Good find. And coincidentally the same connector that's used in my Buick. GM chose the same connector for the amp as the HU, and standard wiring harness connectors will fit if you choose to eliminate the stock amp as I did.