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Cd player install - Reverse polarity

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qpsdubber Learner Dubber

2 posts · joined Mar 2010 ·

#786373
Just a quick question for the auto electricians amongst you..

I have had some electrical work done on my 72 Beetle, by an auto electrician. I wanted to have my Pioneer cd player installed in the car. The auto electrician has told me that when the vehicle was made 12v the polarity was not reversed, therefore the stereo keeps blowing a fuse everytime it is connected and earthed properly.

Is there any truth to this? If so how is this done, because when the stereo is connected to the permanent live and switched live and earth it simply does not work.

coldwindblows Learner Dubber

15 posts · joined Jun 2010 ·

#786374
i would suggest if thats what happened when they did the switch to 12v (ie, earth to positive, positive to earth) you would have a few more problems than stereo ones.. Ie, lights not working, indicators, coil... unless im mistaken?

in any case... just get out a multi meter and see whats happening there.. so, test the perm power, should always have 12v across it. Check the switched live, should only have 12 v across it when the ignition is on.

as for the ground, you can test this too. with the multi meter, you need to check wires with a known ground, it, the chasis of the car. then check with the ground wire the electrician has supplied..

sounds like he hasnt quite explained himself correctly..

but ive installed a few of these things before, not in a beetle. i wouldnt think you have reverse polarity problems, just a dodgy wiring job...

hope this helps?

clinker42 Officially Full-On Dubber

381 posts · joined Aug 2008 ·

#786377
Ye thats right, there are some factory cars from around the world that are positive earth, but everything is different. Look at your battery, does the negative terminal go to ground?

Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 ·

#786378
is it a brand new CD player?
a 72 was factory 12 volt and euro cars were never positive ground so if its blowing fuses its wired up wrong or its stuffed

qpsdubber Learner Dubber

2 posts · joined Mar 2010 ·

#786491
The stereo is brand new, and works fine when connected to a battery by itself. But when placed in the car and connected it does not turn on.
There is power going from the permanent live (I tested it with with a voltmeter) same with the switched live.

The only thing I can think of is that because the car is ground to the chasis that this is the problem. I have no idea............. (sorry guys I am definately not an electrician, give me mechanics anyday!!)

vw59 Turbo Boy

79 posts · joined Jan 2003 ·

#786509
Try connecting the stereo to the battery as you previously did out of the car (stand alone).

Ensure you have the positive wires fused. Then connect a wire from the negative terminal of the battery to the stereo casing.

If the fuses blow then yes the stereo has a short between gnd & active.

If the fuses's don't blow I suggest the casing of the stereo is touching on a positively powered cable/ terminal when installed in the vehicle ie: headlight switch, wiper switch.

Hope this helps
Cheers
A 12 sec street car that is street driven!

Joel Now containing 100\% E-Wang

9,368 posts · joined Feb 2006 ·

#786510
If the battery neg cable is bolted to the chassis behind the battery then its still a neg ground system.

Anyway noone in their right mind no matter how electrically challanged they may be would completely rewire a vw to be pos earth.

Theres gotta be reason why its only popping fuses in the car and not on the bench.
either theres a wire getting pinched somewhere or hooked up wrong and creating a short or its overloading that circuit which I cant see possible with a modern headunit, they just dont draw that much and usally always have their own inline fuses anyway

grumble Son of Jim - Creator of Good

2,672 posts · joined Jun 2008 ·

#786515
Joel wrote:If the battery neg cable is bolted to the chassis behind the battery then its still a neg ground system.

Anyway noone in their right mind no matter how electrically challanged they may be would completely rewire a vw to be pos earth.

Theres gotta be reason why its only popping fuses in the car and not on the bench.
either theres a wire getting pinched somewhere or hooked up wrong and creating a short or its overloading that circuit which I cant see possible with a modern headunit, they just dont draw that much and usally always have their own inline fuses anyway
Sometimes the wiper or hazard wiring will be crushed by the stereo or pushed up onto the wiper mechanism as there is not a lot of room up there.

bnicho Wolfsburg Wizard

436 posts · joined Feb 2009 ·

#786624
If the auto elec thinks your 72 is positive earth, then you are using the wrong auto elec....

Some british cars were positive earth into the early 70's. I personally blew up a negative earth stereo in 1990 when I wired it into a positive earth 1968 Mini.

There is definitely a problem somewhere else, as others have suggested above.
Brett Nicholson
Melbourne, Victoria
1974 VW Superbug L - Olive 😎
1971 Morris Mini Moke - Mopoke
1966 Austin Mini - Audrey
1965 Morris Mini Traveller - Trixie
2007 Land Rover Freelander 2
2009 Nissan Pathfinder

rob53 Officially Full-On Dubber

385 posts · joined Jan 2007 ·

#786629
grumble wrote:Sometimes the wiper or hazard wiring will be crushed by the stereo or pushed up onto the wiper mechanism as there is not a lot of room up there.
+1
Thats not rust, it's ah ... orange primer ... yep that's what it is ...

68AutoBug Beetle Restorer - Experience over 138\% - YIKES --

11,654 posts · joined Aug 2002 ·

#786717
Are You sure He was an auto electrician..??

Well, there was an auto electrician in Scone who knew nothing.... He was retrained after being hurt in another job.
How He got the new Licence??? I don't know..

He used to ask me questions...?? that He should have known
the answer if He knew about electrics in cars/tractors etc...

I've only ever seen Positive earthed cars in the late 50s-60s
they were all pommie cars.. Morris-Austin-Wolseley-Triumph
etc...

some radios could be switched, and many others were not earthed to the chassis of the Radio...
the Positive and Negative wires were used... [no earth]
and speaker wires should NOT be earthed either... IMHO

LEE



qpsdubber wrote:Just a quick question for the auto electricians amongst you..

I have had some electrical work done on my 72 Beetle, by an auto electrician. I wanted to have my Pioneer cd player installed in the car. The auto electrician has told me that when the vehicle was made 12v the polarity was not reversed, therefore the stereo keeps blowing a fuse everytime it is connected and earthed properly.

Is there any truth to this? If so how is this done, because when the stereo is connected to the permanent live and switched live and earth it simply does not work.
- Helping keep Air Cooled VWs on the road - location: SCONE in the Upper Hunter Valley - Northern NSW 320 kms NNW of SYDNEY---

barls Administrator Causer of Chaos and Mayhem

9,473 posts · joined Jun 2004 ·

#786744
didn’t they all go 12v around 67.
i know mine is 12 volt with the negative being the earth and its a 72
“We all pay for life with death, so everything in between should be free.” Bill Hicks
the chaos project - click me

Smiley Veteran Volks Folk

2,125 posts · joined Oct 2008 ·

#786747
barls wrote:didn’t they all go 12v around 67.
i know mine is 12 volt with the negative being the earth and its a 72
1968 was the first year.


Smiley 😎
If you said I was a Volkswagen man, you'd be right.

jacky_moo Seriously Crusin Dubber

115 posts · joined Feb 2010 ·

#789325
On the same track my cd player crapped itself a few weeks ago after changing the speakers over.. was running boxed 6X9's as a temp fix and the system was working fine with the engine running etc but as soon as i cranked the volume the head unit blew... fuse is intact but theres no life in the headunit 🙁
schnell!! schnell!! schnell!! schnell!!