sup guys just became a new proud owner of a 1990 si the question is why dosent the radio work any more when my homie sold it to me it use to have a working radio and hepulled it when he sold me the car now the radio doesnt i connected a new one and it turn on and then turns off then i got a tester and checked for dc power it it only marks 12v sometimes is there a relay or something some where let me know thanks

 

Please tell me you didn't make over 2000 posts without using a single comma or period. I want to help but I can't follow your message.

 

check the under dash fuse, it's one of the 15 amp ones, i think it's the upper one. is the origonal radio plug on the car, or has it been chopped?

 

OMG That's hilarious.

As for the Radio issue I was having the same problem. You checked the voltage already so that was going to be my suggestion. Mine ended up being my alternator over charging.

 

Make sure that you get a proper wiring harness, and wire it correctly. On the red wire you should get 12v only when the key is in the on or acc position, the yellow wire should have 12v all the time.

 

my bad guys that i dont use propper punctiation i just hate using it. As for the radio i did check the fuse, but i did notice a little black relay behind the radio is that have anything to do with it,

 

oh and it dosn't have the OG radio harnes they choped that b!tch UP

 

you and your 'homie' could fix it simply.
run 2 wires off the positive terminal into the car.
take the 12v+ constant and attach it to one.
take the 12v+ switched and put a toggle switch between that and the wire running off your battery.
then your deck has power to it when you flip the switch.
either that or find the problem by redoing the entire electrical system in your car.