possible to install 2 Decks in one car?

Well, there may be another way. If you plan on using a amp to power your speakers, you could use an automatic audio switcher like this one. You would also need a line output converter to get your OEM headunit's audio signal to the amp. But this would only apply if you are going to be using an amp to power your speakers. Duane...

If you think you're confused, imagine how you feel.   

Wow thats amazing. Good luck with your project

Wow thats amazing. Good luck with your project

jimmeezgolfvr6, I do intend to use both decks, just not a the same time, The JVC I'll use to listen to mp3s + radio and the OEM is for the red blinking light and also for the factory alarm, its not a REAL alarm but u guys probobly hear the horn go off consistantly if you open the doors without the keyless remote or key. Anyway, I just need to switch to the OEM deck for the anit theft device when I park at night or whenever I need to for a lil security. jimmeezgolfvr6, thanks for the advice, so you are saying I can use the 2 decks at the same time without conflict or do I still have to manually switch between the 2.     (personally, I rather just have both working at the same time to eliminate the hassel.) thanks

you can use the remote turn-on wire from the jvc deck to trigger the relays. you can wire your oem deck's speaker outputs to normally closed on the relays, and have the jvc's speaker outputs on normally open. that way, when you turn on the jvc deck, the speaker outputs of your oem deck will be isolated. you can even leave that oem deck on but you won't hear sound from it. then when you turn off the jvc deck, the relays will switch back so that you will hear sound from the oem deck. if you're planning on using the 8 spdt relays, here's what each relay will look like: #86 = remote turn-on from jvc #85 = ground #87 = 1 speaker output from jvc #87a = 1 speaker output from oem deck #30 = 1 speaker wire leading towards speaker if your need for the oem deck though is to have the flashing light though, you can save yourself a ton of trouble and just connect constant +12v, +accessory, illumination, and ground to it and be done. just make sure you disconnect everything else to it. good luck!