Voltage Drop

I resently put in a head unit in a friends old fire bird and a certin times the head unit powers down suddenly and then turns back on... it will happen when he turns on head lights or when he shifts out of park..... i tested the # of volts going to the head unit and sure enough i watched my muti meter go from 12 to 9! then back up..... i figured i could use a capasator to fix it.  Does any one see any thing wrong with this set up im about to do?

what does the meter show on the battery when the car is running, if the car is off and it does that could be looking at a bad cell in the battery, but there is defentliy something wrong with charging system, need more info i.e. whats the voltage when the car is running,how is it wired, cripmed together,soldered, wire harness, also wheres the ground ..

yea that doesnt sound like something i would just slap a cap on, Head units usually dont draw all that much current so look into the battery voltage and see if that does the same thing.

I had the same problem with my 68 Barracuda. I found out that when you went past REVERSE, the backup lights coming on for a second with the headlights on, drew enough current to kill the electronic radio. This would only happen at idle when the alternator didn't put out enough to keep it from happening.. The fix.. several things 1. Upgraded the alternator to one that put out more at idle. 2. Rewired the radio to a better hot lead (one not attached to something like the airconditioning fuse or something else that pulls alot of amps) 3. Put the headlamps on a relay system. That kept the headlamps from pulling through the dash wiring and made all my interior wiring much more reliable. Dash lights burn brighter now, radio doesn't cut out, etc... Good luck! Rob Robinson

Im not talking about a really big cap like a 1/2 f  or some thing i picked up a small one at a electronics store i think in is like 500 uf (micro frauds)

it shouldnt need a cap for that... thats a wiring issue... go thru and look for a loose connection.  thats most likely the problem.  I need quality equipment, feel free to donate.

its farads to begin with... a cap is not the answer to the problem...wire the head units constant lead directly off of the battery, and do as BigBlue suggested and relay the headlights...if this problem persists beyond that you will really need to hunt down the problem in the car...there is more than likely a loose connection or short or something somewhere in the vehicle that is causing this to happen... people who dont understand what a cap is for shouldnt be using them...

make sure u have a clean ground connection to i had voltage drop when i had a bad ground, probably easiest solution though would be to direct wire to the battery with a fuse, it won't go out then garenteed

HAHAHAHA to all of you i checked the conections and every thing was fine so my choises were make my friend buy a new alternator to fix a small prob. w/ his head unit or try the cap... a guess what i hooked up the cap and every thing works fine in fact better than fine... his head unit not only doesnt turn off any more it stays on after he turns the car off, for about 5 sec. and he thinks that is so cool!!!! (i wired it to the acc power lead) so hahaha to Big Purds... ya i know what a cap is and how it works... just cause i dont know how to spell farads doesnt mean any thing...