Car Cuts Out With Stereo Turned On...

Evening folks,

Have a weird one here…

I've put this one in 'Electrics' purely because I'm sure it's electric related.

Installed an Alpine head unit in the dash back in April. (there was no stereo before then)
The original stereo wiring had been butchered by the previous owner so I cut the original plug off, put a meter across the wires to determine what was what and fitted an ISO connector to the original wiring. Only thing I haven't done is ran a switched live.

Anyway… when I first connected the radio, I took the car for a test drive. Literally 15 mins from home, the car cut out. Not a fuel starvation kind of cutting out. I mean total loss of power. Alternator light flashed and engine just died.
Managed to get the car home and disconnected the head unit as a process of elimination. This seemed to sort the problem and car drove fine after that and has been until today.
I decided to give the head unit another try and re-connected it this morning. Same problem… Car died on the other side of town. Not convinced the stereo was the problem, I managed to get the car started but the revs instantly dropped and engine died. Disconnected the radio, started fine after burning off the unburnt fuel and carried on to work.


Short of putting a meter across the battery to measure voltage with the radio on, I don't know where to begin with this one.
Any ideas?
Is the head unit drawing more current than the circuit can give?

Yes you have got a weird one and I haven't got the foggiest idea to boot.
But I might know a Man who does!    

Calling rubjonny  

very strange, the only wires you'll have originally on the mk1 stereo plug is red for live and brown for earth plus you may possibly have a grey/blue which is dash illumination and unused on most modern headunits. if its a late cab or has a power hood theres a thin brown/red which is key-in-ignition live which you can use for your accessory feed. and in very rare cases you sometimes have a white/yellow wire which is speedo feed from clocks, but only there if you have cruise control or expensive aktiv radio system (speed sensitive volume control, again unused on modern headunits)

anyway if plugging it in causes this and you have the live and earth right i can only think its drawing too much power and your alternator is too weak to cope, unless some other wirign bodgery has gone on behind the dash and something else has been tapped into the stereo live that shouldnt have been, the only other feed on this wire should be the ciggy lighter socket

Hi John,

Apologies for the late response, and thanks for your reply.

It definitely is a strange one…
You are right, the radio wiring does only consist of three wires:

Red, Brown and Grey/Blue.

I did double check to make sure that the live and earth are the right way around and doesn't appear to be any issues there.
I came to the same conclusion about the alternator being too weak to cope and the next troubleshooting step is to measure the voltage with the headunit plugged in.
There was an immobiliser installed when I first bought the car. This wasn't working at all and had been bypassed at the ignition switch. It was tapped into the ciggy lighter feed but the immobiliser has since been removed along with all relative wiring. The original wiring remains intact.

I'll have a gander at the weekend to see if there is any wiring bodgery behind the dash and let you know what I find.

Thanks for your help mate. Much appreciated!

The symptoms you describe are exactly like those I had on a MK2 Polo Coupe, donkey's years ago.

Unbeknown to me prior to my buying the car it had been extensively repaired, including repainting the engine bay.

The cause of my cutting out was eventually traced back to the earth strap which had been reconnected without rubbing back the new paint so as to get a sufficient connection to the body.