music from radio fades in and out

[DongDong]

hello fellow celica supra owners! my supra now, when i listen to music, fades away and fades out. it would get louder when im over 30 mph. but when i slow to a stop, its like someone turned down the volume on the car. whats going on here?!

[Tanya]

WOW< weirdness, are you watching your volts? If you slow down, do you notice your volts go down more than usual?

[DongDong]

the volts stay between 12 and 18.. thats strange i dunno whats going on! someone help!!

[suprasrock]

Have you got the original fitted radio or something else? I've seen some sets (Hitachi I think) that alter the volume to compensate for background noise and therefore get louder as you go faster.

[DongDong]

i checked the power level when the engine is not turned on.. 12.5 volts. when the engine is running, the power is 14 volts. wtf?!

i do not have the OEM radio. i bought an after market one. this only started happening a while ago. wtf?

[Solo1Supra]

Voltage is reading higher because the alternator takes over when the engine is running.

[suprasrock]

Your battery is flat, that won't help any. A good condition, charged battery should be 13.5 volts off load.

[onephatcrackaII]

13.5??? mine is 12. something volts.... but nothing is wrong with mine..... why is everything in a car made for 12volts if its 13?

[suprasrock]

The 'open circuit' voltage of a healthy battery is about 13.5v to 13.8v.
12v is the 'nominal' voltage and what you would measure when the battery is loaded up but not connected to a charging circuit. It is a characteristic of lead acid batteries (and other types to some extent) that the voltage drops as current is drawn. The batteries are designed to give 12v at full rated load and therefore will measure higher when not connected. Accordingly, charging circuits deliver around 14v and all the electrical equipment in the car should be designed to work with anything from 11.5v up to 15v. :)



and yes, I am an Electrician 8)

[onephatcrackaII]

ohh ok ha... yea my dad's an industrial electrician and i asked him about it and he said the same thing ( after looking at me like i was retarded haha)

[suprasrock]

Right, I'm industrial as well but batteries are kinda basic stuff for us.

It's not a dumb question. A lot of people see 12v written on everything in a car and quite reasonably expect the voltage to measure 12v.

[dogstar]

i used to wonder about that all the time, till i played with an electric motor...
it was quite happy to operate with anything from 6.5-24 volts.
the more voltage you gave it, the faster and hotter it would run, but as long as i kept it cool, it survived.

then i discovered those folks who build battlebots sometimes use a 24 volt reserve battery for "emergencies" and kinda thought about it, so i started doing some research.

seems to me, most electrical components can handle a certain amount of over power, as long as theyre kept cool.

electricity is fun.

[batmobile]

Alot of times its the amperage you have to worry about. You can load up the voltage without the motor blowing, but if you increase the voltage and the amperage then you have more watts, more watts equals disaster with electrical stuff. V *A = watts.