Hello,

I had this unit in my SKODA FABIA 2000 working for few years

this car provided 2 sets of ISO plugs (speakers + power) and HU worked straight from box I just switched red and yellow to rectify memory issue.

I tried to put this unit into my new car skoda octavia 2002 this car again provides duo of ISO plugs (speakers + power) but this time HU wont turn on so I benched tested the HU and didnt power on (yellow with red in + and black in -) so I assumed HU was faulty and bought another one I plugged it into the car again not working.

Things Ive done so far.

-Checked fuses in the car and in HUs they are fine everywhere

-I measured +12V constant and ignition +12V against ground on the ISO connector

-Switching red and yellow cable didnt do anything

In order to switch on this HU I have to just connect ground and constant and ignition and it should turn on right?

Things I have heard and dont think they should have any effect.

Connecting antenna- I dont think that is related

Grounding chassis of the Headunit directly to metal part of the vehicle. Havent tried yet and dont think it is necessary either.

Any other suggestions apart from both HUs faulty because that is highly unlikely.

thank you in advance for suggestions

damn... I had been having problems putting a new head unit in.... I was saying my fuses were fine, I was counting to the wrong fuse in the car for the audio and that was my problem !! , finding and replacing the right fuse worked...(I swapped the wires to get the memory working) .....

 

BUT if you have checked the feeds , fuses isn't your problem....

 

you are right in saying attaching the antenna isn't ness for earth....

 

 

I would say that maybe, however unlikley, both head units are dead?

 

can't think of another reason.... there was no reason when I had problems, hence an overlooked fuse..... (I tried 3 head units before I decided it was something else!!)

 

good luck! its as frustrating as hell!!!!

I would start by running a temporary ground cable to the body to see if you get power to the unit, if you do, your in loom earth has failed somewhere.

I dont understand how could have earth failed when I measured full 12.54V against it?

Anyway Ill try...

Edited 21 June, 201610 yr by Entalpie

In which case, I would do a multimeter continuity check between the loom earth pin and the body. reading your original post, it wasn't clear what you had used as an earth for the readings.

 

A lot of head units use the antenna lead as an extra earth, as it earths to the body on the vehicle.

 

I know when we put an aftermarket unit in my father in law's 51 plate fabia, I had to trace the earth back in the loom as it had separated or been damaged by the previous owner.

 

Just a silly thought here, your iso cable from the radio is definitely keeping the cable orientation to the wires in the loom - i.e live red on the radio is going to live on the loom, and it hasn't got a different orientation from the Pioneer loom?.

somebody must have done something with cables as I found ignition cable connected to red wire and then original yellow +12V constant battery disconnected which gave me nothing against black earth in loom (key in ignition) still before I found out about this I had normal constant on red wire and ignition(which is that additional cable) to radio connected and didnt turn on.

So I have standard ISO with 8 cables 5 (+12v const +12v igni ground ilu antena booster) which are normal for headunit but in the back(there in the radio compartment in that space where cables are coming out) yellow constant is disconnected and both constant and ignition have their red wire. That was taped with different adhesive tape as Skoda uses cloth adhesive tape.

I measured live wires in ISO against black cable earth in ISO loom I measured just voltage (as current would short circuit it). = 12.54V

By continuity you mean impedance that one with beep?And to measure ground impedance in ISO LOOM against something metal which is grounded to battery?

I had to buy aftermarket loom for pioneer which is 1st thing which Im not okay with but Ill survive it on the pioneer there are 2 pins which are bigger by size +12 and ground then second from left is yellow which is memory then illumination and antenna booster (blue and orange cable)and brown which is mute with bare end not connected to ISO (Im leaving out speakers pins) these copy configuration in ISO loom from car blue on blue orange on orange and black on black and yellow leads to red and red to yellow which is not a problem as I switched that in couple of times and does not change anything on both instances I turned key in ignition to verify.

Now back to earth/ground problem so I understand that multimeter when its measuring voltage it really needs just couple of miliamps to show that full 12.54V so youre suggesting that thing such as headunit during its initiation taking few amps but because that earth is poor impedance is higher thus those few amps are not enough to maintain 12V thus voltage drops bellow 12v and unit wont turn on as a result?(please correct my statement if necessary)

Edited 21 June, 201610 yr by Entalpie

By connecting antenna plug thus part of the current would travel through antenna negative/ground back through chassis of the car to negative pole of battery?

Essentially the last paragraph of yours just about covers it, you may not be able to pull sufficient current to run the unit if the car loom has been compromised by poor connections or worse still chaffing damage to the loom itself. The continuity beep test should be adequate to prove a circuit, but a second temporary earth run from a good body point would eliminate any degrading of the internal loom earth.

 

If you have any pictures of the loom area it may become clearer of what may have happened here?.

Okay ill post photo later.

Continuity measured black negative in iso loom against metal part gave me reading 00.5 to 00.4 = between 0.4-0.5ohms..

So 12v wires leading from dash are Yellow Red Red

Yellow is marked constant but instead is switched, then both red are marked ignition but one is switched and one is constant. In final Ive got 2 switched and one constant cable tried to connect them to radio in combination with ground but no avail with connected antenna via reduction didnt help either.

Last thing which Im going to investigate is that aftermarket loom for pioneer which may have swapped memory cable for different position no other things come into my mind then both faulty units which is unbelievable..

Edited 22 June, 201610 yr by Entalpie

Last update

loom seems to be fine Im really desperate here only other thing I found out is that some guy with Punto MK2 had problem with PIoneer needing some canbus adapter which sounds to me absolutely unrelated...

Problem solved both units faulty...by quick look by external person some IC chip is burned

thanks everybody for some input.

^^^ my answer glad you got it sorted, can be as frustrating as hell! lol..