Amplifier only works when car is turned off or when i hit brake!

 

New member
Username: Waldolandry

Post Number: 1
Registered: Nov-05
ok . . . where do i start. Alright, i have two 10 inch subwoofers in a box in my trunk one of them is powered by an old MTX amp which works fine except that the speakers are rated at 300RMS max and the MTX is 70RMS bridged, lol. Anyways, the other sub is powered by an SPL somethin or other (one that doesnt work most of the time) which bridged puts out 300RMS they are both hooked up bridged. I have a dual amp kit where the power wire goes from one 4 guage to two 8 guage. The ground is also 8 guage and i have it jumping from the SPL to the MTX. Now that i have "set the mood" so to speak, here is my problem. When i turn the key to only turn the radio on, the amp works fine, most of the time, but when i start the car and idle it, it doesnt work, after driving for a while with it like this i have come to the conclusion that when i am coming to a stop (or idling around a parking lot or something) and i press my brake pedal it kicks in and blows my mind with its insane bass pumping action. so in other words it only works when the cars off and when i hit the brake sometimes (and no, never when i hit bumps . . . thats what i dont get). It makes no sense to me and i figured well, why not ask a pro . . . so i went to Hardcor Audio, a car sound system shop who has been there for me from the begining, answering my dumb questions with answers that always worked. Except this time they were stumped . . . never seen anything like it in his entire life . . . he said try it in someone elses car system and see if same thing happens and that brake pedal thing must be a coincidence (but its not, i tested it for 5 minutes at wal-mart parking lot . . . idling around . . . hitting brake . . . it worked. So could someone please help me out because im lost. (Hardcor Audio also said that my wiring was correct so i have ruled that out)(nor does the amp go into protect mode EVER)(and even more baffeling is the MTX works consistently)

PS. please forgive my sentance flow im so hung-over its not even funny and those two huge cups of coffee didnt help it at all . . . . . . .
 

Anonymous
 
move your ground wire somewhere else

make sure you have both positives coming from the same place and both negatives from the same place otherwise youll get a ground loop which makes a humm in the speaker (could be front back or subs)

with a dual amp kit you should have enough wire length to connect both ground wires to the same screw

my guess is you have a ground in a 'dead zone' of the car metal and when you press your brake the brake lights create a circuit increase thus charging the dead spot

when you start the car the circuit shifts in some spots considered a bad ground

with the car running all the amperage is being sucked up by the ignition coil and anything else electric under the hood and in the dash

so basically with the car off that dead spot has very weak negative.. but enough to work

when you turn the car on theres other things hard wired to the battery thats stealing what little negative power that little spot of metal had which could be why that amp turns off

if you have both amps grounded to the same spot then one of the amps is more efficient then the other.. my guess is the one that turns on is the more efficient one because its not being stubborn by not turning on because theres not enough negative (takes less power to make the other one work)
 

Silver Member
Username: Cadillacdb

Houston , TX

Post Number: 210
Registered: Aug-05
Try to put a different amp in there an see what happens ... if the different amp works fine then its the amp an a 70 rms amp really isnt worth all the hassle so i would just buy a different amp eitherway ... Maybe get a RF T10001bd
 

Silver Member
Username: Cadillacdb

Houston , TX

Post Number: 211
Registered: Aug-05
The only reason i say T10001BD is because i saw one on ebay the other day that was used but still had its box an everything an the guy was only asking 250 with free shipping an i think thats a steal, He even gave a DOA Warranty
 

New member
Username: Waldolandry

Post Number: 2
Registered: Nov-05
thanks, ill try what you said

now i cant wait to get to work and back.
 

New member
Username: Waldolandry

Post Number: 3
Registered: Nov-05
ok i even tried grounding it directly to the frame under the car . . . nothing . . . any suggestions? im on a tight budget
 

New member
Username: Waldolandry

Post Number: 4
Registered: Nov-05
o yea, and when the car is off and i hit the brake it works now and when i let off it does not.
 

New member
Username: Waldolandry

Post Number: 5
Registered: Nov-05
I need help bad, somebody please give me some advice on why this amp is not working. I dont want to be stuck with underpowered subs forever.
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