*Headunit Keeps Blowing Fuses*

[DAVE_RSi]

OK need ur help on this 1 ppl, had me headunit like 2/3 years and never had probs, sony minidisc player

ok on sat i decide 2 wire in the old standard front speakers, goes ok and all is fine, then sunday i turn car on and go 2 turn hu on and no power

fuse blew in back of hu, 10amp, anyway i replaced fuse and blew again straight away, so unwired front speakers and took out RCAs and remote 4 the amp, new fuse in and it works, just powering rear speakers

then get down the road and it goes again???

so what do we think the reason is???

dodgy earth? or 4 sum reason car giving hu 2 much power, or problem actually with hu??

im bit stuck here, the fuse blew this last time with only the constant power going 2 the unit as keys werent in so only power that should have been going 2 hu is the constant power from yellow cable



help pls

.Dave.

 

[DAVE_RSi]

ok after an earbashing from a mod on talkaudio for not posting correctly (shock) i got this reply:


Seriously though, sounds like youve connected the speakers up wrong, perhaps bridging or running in parallel, causing to low an impedence, and therefore too much current draw. Check your speaker connections

Its NOT the earth! Its incorrect speaker connections!

Id suggest you rip it all out and start again, but failing that, there /should/ be 8 speaker wires at the back of the headunit... by playing with fader and balance and a voltmeter, you can work out which wire is for front left, right, rear left and right, and which are positive and negative. Then all you need to do is make sure you connect the right wires to it.





This sound about right to everyone????

 

[Djw John]

Yeah sounds like thatll be it. The only other thing I could think of is a trapped wire when you push th eheadunit back in causing it to short.

 

[DAVE_RSi]

trapped wire eh, that could be it then as there isnt much room behind my hu so it does need a gd push back in!!

Well looks like ill b buying a voltmeter 2nite and starting everythin from scratch, just what I bloody need :-(

ohwell aslong as its fixed by tomorrow,
Nice hour long journey and I wont b able 2 handle it without music

my lil portable radio just isnt cutting it

 

[Pete]

I doubt its a shorted speaker wire tbh, the hu should have an in built cut off seperate from the fuse to stop it from frying itself in that situation. More likely to be a crushed wire when you push the unit back.

 

[DAVE_RSi]

hmmm i couldnt c any that were crushed really, apart from 1 speaker wire that wasnt connected 2 anything

will unwire everything and use a voltmeter on it bit by bit, will be swearing constantly, clio seats are hard 2 sit forward it and my hands shake like a leaf when im stressed and trying 2 do fiddly stuff

will check what powers going through constant and ignition power and then will just try the fuse in with power just to hu, with it not powering a thing

then will wire up 1 speaker and c how that goes, stupid sodding thing aint it

 

[DAVE_RSi]

OK UPDATE:

I disconnected everything, put 10amp fuse in back of hu, then connected up the plug that goes in back, so it had yellow,red,blue,black wires connected

fuse blew straight away so its not 2 do with the speakers, so what could it be?

The ignition wasnt on so only should have had constant power getting to it!
So now what? I am prob guna get a voltmeter in a minute and check power that is coming from constant wire and also ignition wire

any suggestions what I need 2 do

cheers
.DAve.

 

[Dink]

have you tried it with out the blue one connected??

get a multi meter and put it on continuity and check between the case of the hu and the wires going in

 

[DAVE_RSi]

havent got a multi/voltmeter gota go buy 1 soon

just had a play after being advised on talkaudio,

Isnt the blue wire only there 2 tell hu when 2 turn on off etc?



Ok this time, I disconnected negative, put new fuse in hu

pushed plug in back of hu, fuse is fine, reconnect neg on battery and fuse blows

so then disconnect batt neg and disconnect yellow wire, so only got red,black,blue connected

connect batt neg and fuse is fine, turn keys and hu has no power 2 it

so this time do the same but only have yellow wired in instead of red and it blows assoon as neg on batt is connected??

this point fingers 2wards faulty yellow wire??

 

[Dink]

nothing would blow without the black wire connected

so yeah the yellow does sound dodgy. i believe that this is what is used to power the internal amp

 

[dangermouse_se]

If the fuse in the HU is blowing mate it isnt wiring thats at fault.

If the yellow wire was shorting to earth then there would be no feed to the HU.

If you want to test it connect a pos (with its own fuse) to the battery pos and one to the neg and connect em to the HU. See if the HU fuse blows.



If it does...repair shop or new HU.

You probably shafted the internal amp when you connected the speakers wrong.

PS for info standard wiring colours for radio:

Red - Accessory live (on/off with key); Yellow - Permanent live (for memory etc.); Blue - Amp remote; Black - Earth

You may also have telephone mute and/or illumination.


[Edited by dangermouse_se on 21 July 2004 at 8:41am]

 

[DAVE_RSi]

yea there the wires ive got!!

so worth getting lots of wires and going straight from battery to hu and c what happens, and hope it works, if it blows then hu is at fault, if it doesnt blow then its the wiring b4 it gets 2 the hu??

so i need 2 wire up a + wire from pos battery with 10amp fuse in it, and attach wire to yellow cable from hu i take it
and also attach wire from neg battery to the black wire from hu




Ok I have a voltmeter thing, Unfortunately I dont really know how to use it :-(

Ok so basically I need to test the Earth, ignition power, constant power, and blue wire

So i set the voltmeter on2 10amp setting first, then disconnect car battery??

then attach up voltmeter points to black wire earth and then to yellow wire, then connect battery and see what reading i get

as you can tell im useless at this and havent used 1 before so need some guidance

i.e. what im connecting up and what figures im hoping to get etc

Thanks
.Dave.

 

[DAVE_RSi]

from talkaudio:

Find a suitable earth (something you know is DEFINITELY earth) - run a wire from the negative terminal on the battery if necessary. Then put the earth probe from the multimeter onto that, and the positive probe from the multimeter on the other wires youre testing.

The permanent live will be live (show 12.0V plus) with the ignition on AND off
The ignition switched live will only show a voltage with the ignition on... when its off, itll read 0V
The earth will read 0V with ignition and AND off
The remote (usually blue) will show 12V when the headunit is on.

HTH

Mark


so if i get a different figure of 12v from the yellow then i know thats the problem??

 

[dangermouse_se]

Okay this is what I would do mate:

Connect a live from the battery (with a fuse) to both the red and yellow wires from the HU and neg from the battery to the earth. If the radio you have wiring fault. However I doubt this will happen as the fuse is blowing in the HU, as I said any short before the unit would not blow this fuse.

The other thing to try which is a bit fiddly is connecting the battery feeds straight to the radio pins to eliminate the radios loom.

Testing the wires for shorts. Disconnect the battery + but leave the - attached:

1. Set the meter to ohms

2. Connect the meter to the switchable positive feed to the radio and the other end to the battery negative or a good earth. Reading should be infinity. If it is 0 or a low number you have a short.

3. Repeat as above for the permanent live.

4. Repeat as above for the earth but in this case you are expecting a low reading.

If you get stuck PM me mate.

 

[DAVE_RSi]

ok cheers m8, will have 2 try it later, working till 1pm

then got hour drive with no music to do fireservice written tests, im hoping its just wiring

if internal fuse has gone what am i looking at roughly 2 fix, its a 3 yr old sony minidisk player

 

[dangermouse_se]

Not sure M8. You would need to take the unit to repairer for a quote.

[Edited by dangermouse_se on 21 July 2004 at 10:37am]

 

[DAVE_RSi]

Ok UPDATE:

first of all I tried using the voltmeter, wonderful stuff, attached neg from battery up to the neg of voltmeter, then i attached voltmeter + to the yellow wire

readings of 16 basically, and everything got hot pretty fast

tried same with red wire, and got no readings at all with ignition on and off


Then i moved on 2 a different idea, and I ran a wire from neg of battery to the black(earth) wire at back of hu

Then i ran a cable from + of battery to a 10amp fuse, and then 2 attached wire to both the red and yellow wires from hu, and sure enough, it got power and nothing blew, also played speakers!

so at moment ive taken everythin apart again as im not sure what its best 2 do and whats the actual problem, from what ive just said can I eliminate some problems and point fingers at certain possibilities??

cheers
.Dave.

 

[Dink]

16 volts is this with the engine off???

the fuse in the back of the hu would only blow if there was an internal fault (could be to do with the 16volts?? )

now it seems strange that everything got hot

 

[DAVE_RSi]

yea it was a bit worrying m8,

the wires from the voltmeter were really hot, almost melting hot

that was just testing the yellow wire, so must be problem with yellow wire??

yea 16v i think, i was told that it should be between 12-15ish

sounds like hu is ok though, sounds like its just a problem with the constant power cable, strange that its overpowered?

will have 2 wait and c what talkaudio bloke tells me in the morning

.Dave.

 

[Dink]

you didnt have it on amps did you???

yeah it should be about 12.3- 12.8 (off) 13.8-14.4 (on)

 

[DAVE_RSi]

rite well talkaudio site mod has came out with this:



Well, sounds to me like the red is probably your illumination (i.e will go positive when the headlights are switched on), so test that.

Black is definitely your earth

That leaves yellow, and what other colour? Yellow and the other colour will be permanent and ignition live, assuming your above info is correct (I think).

Its never a wise idea to just connect power to random connections btw... you really should have followed what I said.. youd have had your answer by now...



seems a bit weird really 2 b honest, why would everything work fine then now go wrong, surely if id connected it wrong in first place 2 months ago then id have had probs straight away and not all of a sudden

well i guess i will test things 2mora with voltmeter,

will test red wire from car, with lights on and off, ignition on and off

and then do the same with the blue wire



If things are still pissing me off and not working then its just pointing 2 that yellow wire from car, giving 2 much power 4 sum reason all of a sudden

 

[dangermouse_se]

Sounds like that could be it, you def had the meter on VOLTS?

 

[DAVE_RSi]

i tried voltmeter thing on all settings and only place i got reading was place i used it in and it was 16 with engine off and with engine on it was giving 17/18

so i take it , it must b volts??

im not 100% though so im guna tlk 2 a m8 and get them 2 help me as im not 2 gd with voltmeters etc

I dont think its what talkaudio mod has been sayin, hes making it sound like ive mixed wires up, but its been fine for last 2 months up till now

everything points 2 the yellow wire so why do we think it could be giving out excess current???

and if i cant fix the bugger whats best 2 do, make a brand new constant live

was fun yesterday, getting a wire, attaching it 2 batt +, then attaching that 2 a fuse, then going from fuse 2 red/yellow at back of hu, lovely bodge job but it gave hu power so i was happy

 

[dangermouse_se]

Dave

Sounds to me like you had it on amps. Theres no way to 16 volts in a wire unless you have sixteen volts at the battery unless you have fitted a transformer (and I doubt you have!).

Running a new wire might be the easiest solution although you have to wonder if owt else is up.

If your mate cant help PM me and Ill pass on my number so I can talk you through it.

 

[DAVE_RSi]

ok m8 cheers, prob best if i find a pic sumwhere of the voltmeter thing ive got aswel

was 13.99 from halfords, pocketmeter i think its called

will c if any1 can help, if not will PM ya and give u a call
its just worrying that when testing the yellow wire it gets hot, very hot very fast

only got probs since i wired up front speakers aswel, so possibly put 2 much pressure on it, was trying 2 take 2 much power, i dont know :-(

 

[dangermouse_se]

Wires get hot from current not voltage bud.

If the meter is set to measure current (amps) its has virtually no resistance where for measuring voltage the resitance is high. If you connected the meter to the yellow and to earth and set it to amps with no load on it you effectively shorted the battery and your lucky nothing caught fire!

If you want to check for short circuits follow the instructions I gave you regarding resistance measurment. This is the safest way becuase the battery is disconnected at the + so you are testing with a small current from the meter.

As I say PM me and we can look at it later on.

 

[DAVE_RSi]

http://www.gunson.co.uk/acatalog/pocket.jpgU face=Arial color=#0000ff http://www.gunson.co.uk/acatalog/pocket.jpg/U







well thats what it is, gunson pocketmeter 1



couldnt find any better pics on the net

 

[dangermouse_se]

Looks like itll do the job.

 

[DAVE_RSi]

ok new problem, havent drove car in dark 4 few days,



now 2nite im set 2 go home, start car, turn on side lights, no dash lights come on, passenger side lights dont work, turn on headlights and fronts r now ok but only 1 rear works, still no dash lights apart from light sayin i have headlights on

whats happened now???

another fuse gone, what the hell is going on, startin 2 piss me off now

 

[dangermouse_se]

Sounds like there is either a short somewhere (you may have disturbed some wiring trying to fix the radio or the alternator is US and is spiking. Check the alternator output at the battery, with the enging on it should be 13v ish.

In all fairness mate I think you arent gonna fix this yourself. Better get it looked at.

 

[DAVE_RSi]

yea i know, geting out of me depth, will check battery output when i get home, then its time 2 ring an electrician and get me wallet out :-(

just hoping its sumin simple and cheap and not sumin sstupid like new alternator

 

[DAVE_RSi]

Rite ok tested battery and got

with engine off, 12.97 volts with engine on 13.80 volts

that sound alrite or isit a bit high with engine off

i rang T+Ms in colchester and they said they could look at it saturday if i want but its like £40 an hour labour

and im not 2 rich so not 2 sure yet what im guna do!!
they said could take 1-2 hours prob as they gota do trial and error

 

[Dink]

12.97 is a excellant reading (good batt)

i could have taken a look at it for ya before you start forking out hard cash, if ya was so FAR a way

 

[DAVE_RSi]

Fixed, got help from me mums bloke, used decent voltmeter

hu was shorting, took it apart and blew it with a hoover, our theory was that a lil tiny bit of wire had fallen inside and was therefore shorting it

all works at moment so fingers crossed eh