so my battery and alternator are both brand new along with a few other things about two days ago it started to drop with any accessorys on especially with the defroster on it drops to like 7 volts at idle. but with everything else it only stays at like 10 at idle and jumps back to normal uinder any throttle.

 

is this what your gauge says or what a volt meter/multi meter you have hooked up says

 

I would pop on over to the local Autozone or pep boys and have the charging system tested. This is usually a free test. It's not uncommon for a reman alternator to be faulty i have had it happen. A charging system test is really the only way to figure out what your issue is. They use a machine that checks your charging system under various conditions. It loads the system to check for proper voltage output. Also you dont have underdrive pulleys installed do you? These are one of the main causes of low voltage output. If your charging system tests good then you probably have and issue with your gauge. Also if your defroster is drawing that much current, id say there may be a wire grounded somewhere it shouldnt be. Do an ohm check with a voltmeter to see if this is true. Your output should be around 13.8 volts. If its lower than this id say you have a bad alternator more precisely the internal voltage regulator.

 

It sounds like a bad alternator

 

i put the old alt back in and it reads the same thing. i also noticed idk if this may have something to do with this but when i shut my car off the check engine light and brake light come on and slowly fade away.

 

with that new info its starting to sound like you have some electrical problems. The current draw and what your dash lights are doing suggest this. Go get your charging system tested and go from there.

 

another thing i forgot to mention is the previous ower absolutely butchered the wiring up front near the battery to have the fan constantly on but ive never had this problem until now.

 

UUGGHH hack and slash jobs on cars are sickening arent they? I would venture to safely say that is one of the main reasons for your problems. The sensor and relay to turn on the fan are cheap.(not to mention it takes less effort to replace these than to hack up the wiring) But instead of replacing them people hack up the wiring so the next guy/girl has the headaches. Get yourself a Haynes or Chiltons manual with schematics and study them. Then you will have to make the wiring right to get rid of your gremlins. Best way is to get a replacement harness from the junkyard.