How do I make a constant?

[Serp]

Hi,

I have a 1981 VW Rabbit Convertible. Unfortunately the radio has no constant and I'm not sure how I make one. Do I just make a wire straight from the battery to the radio or do I need to relay it through a fuse and a resistor?

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[keep_hope_alive Premium Member]

for your 12V constant, you'll need a 12-10awg wire from the battery positive terminal, fused at the battery for 20A (12awg) or 30A (10awg).

then you could use a relay off that constant that is triggered by the car's 12V ignition wire - creating a new ignition source. so the HU isn't getting any power from the existing vehicle wiring.

 

[Serp]

for your 12V constant, you'll need a 12-10awg wire from the battery positive terminal, fused at the battery for 20A (12awg) or 30A (10awg).
then you could use a relay off that constant that is triggered by the car's 12V ignition wire - creating a new ignition source. so the HU isn't getting any power from the existing vehicle wiring.

I hate to ask, but could you dumb this down for me?

I understand what wire I need.

How do I find if my battery is 20A or 30A?

How do I relay off the 12v ignition wire?

My radio has power, but every time I turn it off I lose all my stations and the clock and what not.

 

[keep_hope_alive Premium Member]

i made this to clarify

 

[keep_hope_alive Premium Member]

if you use 12 awg wire you need to fuse it at 20A. if you use 10awg wire you will fuse it at 30A. the reason for using larger wire is if you want to add other accessories to it or the relay.

you can use standard ATO or MINI in-line fuse holders available at any autoparts store. They sell primary wire there also. Use Yellow if possible.

 

[hatedonmostly 5,000+ posts]

I hate to ask, but could you dumb this down for me?
I understand what wire I need.

How do I find if my battery is 20A or 30A?

How do I relay off the 12v ignition wire?

My radio has power, but every time I turn it off I lose all my stations and the clock and what not.

lol

You should probably take it somewhere and have someone else do it, because honestly, I don't see this going well for you if you don't understand what he just said. //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[keep_hope_alive Premium Member]

also, i recommend you ground to the chassis or floor, don't use a ground wire from the existing wiring.

 

[Serp]

i made this to clarify

Wow, you kick ***. ^.^

Okay, so where would I buy the relay? Would they have them at just any hardware store?

 

[Volvoboy]

also, i recommend you ground to the chassis or floor, don't use a ground wire from the existing wiring.

So what you're saying is... I should make the ground on my deck longer than a foot and floor ground it?

 

[Volvoboy]

also, i recommend you ground to the chassis or floor, don't use a ground wire from the existing wiring.

So what you're saying is... I should make the ground on my deck longer than a foot and floor ground it?

 

[keep_hope_alive Premium Member]

the relay is a standard BOSCH 30A 5-pin available for a few bucks at any automotive retailer.

consider the entire wire path to bare metal, and the awg of the wire. if it's longer than a foot, that's fine as long as you increase the wire size. it's still a better ground than anything in the dash. you want the lowest resistance to the battery.

 

[keep_hope_alive Premium Member]

the relay is a standard BOSCH 30A 5-pin available for a few bucks at any automotive retailer.

consider the entire wire path to bare metal, and the awg of the wire. if it's longer than a foot, that's fine as long as you increase the wire size. it's still a better ground than anything in the dash. you want the lowest resistance to the battery.

 

[DammitJames 10+ year member]

i made this to clarify

nice schematic //content.invisioncic.com/y282845/emoticons/toast.gif.bc0657bf54b9ee653b6438524461341e.gif

 

[DammitJames 10+ year member]

i made this to clarify

nice schematic //content.invisioncic.com/y282845/emoticons/toast.gif.bc0657bf54b9ee653b6438524461341e.gif

 

[keep_hope_alive Premium Member]

the relay is a standard BOSCH 30A 5-pin available for a few bucks at any automotive retailer.

consider the entire wire path to bare metal, and the awg of the wire. if it's longer than a foot, that's fine as long as you increase the wire size. it's still a better ground than anything in the dash. you want the lowest resistance to the battery.