wiring help

[PlymouthScamp71]

Ok so for the longest time I thought I had horrible power loss cause when I'd touch my gas pedal it would kill my subs and one day I went to pull out and I had my lights on and my subs didn't die! I hooked a volt meter to my amp and idling with no lights it read anywhere from 14 to 15. With head lights and door open it read 12.88 and with the bass turned up 12.. It's an older 1971 Plymouth Scamp and I talked to a audio shop and they said it's a ground issue. Anyone got any other sugestions or which ground??

[dpeebs]

where do you have it grounded to? i had a similar problem before but i would blow fuses i had a bad ground/ not big enough ground. i looked up so many things i though my amp was shot but then i was tlking to tech support for my kicker and they said if you cant ground to the frame find a thick piece of metal or in my case use the seatbelt mount, iv used the seat belt ground with power and ground the same size wire and not a problem yet! also i was told not to ground 2 amps to the same place, im no expert but that may help you a bit