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Why is my stereo fuse blowing?

Hi all. I'm the new proud owner of a T4 which I am doing a few things to.

I decided to replace the stereo as it was the old original one (1999) and I wanted one with bluetooth handsfree and music streaming.

Anyway, the old one came out easy enough, just a firm pull did it so I disconnected it and connected up my new stereo. It wouldnt turn on, so I checked the fuse, all ok, so plugged back in old stereo to check, now that wouldn't turn on.

Everytime I check the plug for power, the 10A fuse blows. Plugging the stereo in doesn't blow it although it doesnt power up, only when I test the plug for power. Negative on a grounded bolt and positive on the power pin in the plug, and pop goes the fuse !

Also the previous stereo would sometimes drop the volume lower when I went over a bump. I would turn it back up and next big bump, down goes the volume again. I didnt notice if it was cutting off power and back on again.

Has anyone got any ideas please? I'm certainly no electrician so in basic terms would be nice :) What I don't understand is why the fuse blows when I test the stereo plug for 12 volts.

Snoop
July 2010

T4 Vehicles, Cars Stereo Fuse Blowing

Good morning. ok I have checked it again this morning and I must have been doing something wrong last night as the fuse now isnt blowing when I check the voltage at the stereo plug! Hmmm tiredness, dark, me being rubbish at electrics, not a god mix I guess.

Anyway there is 12V at the positive pin, I checked the earth and get a circuit from the earth pin to another earth point on the vehicle.

The stereo still doesnt power up when I plug it in. Neither does the new one. Its got me completely bambuzled, help !!!!

Snoop
July 2010

The meter's ok, works elsewhere. Yep I am measuring DC volts. Range set to 20V.

I'll try the lamp test tomorrow. I had a good look at the plug and wires as far as I could see and couldnt see any damage or anything untowards.

The fuse is definitly good before I test. I hear it pop and the courtesy light also goes out at this point.I've gone through 3 fuses now.

I'll also try and find an alternative power supply if I cant sort the original one. Will report back tomorrow.

Thanks for your reply :)

Snoop.
July 2010

This should not happening - measuring voltage with a moving coil instrument consumes micro Amps - with a digital meter even less - my first thought was that you have the meter set to Amps rather than Volts (in which case the fuse will pop) but I'm sure that this is not the case. Might the meter be defective? Do you have access to an alternative meter. Can it measure the battery voltage OK?

To pop a 10A fuse you must by default be causing more than 10A to flow - you might try a test with a low wattage auto lamp - 50W will draw about 4A and the fuse should not pop. Inspect the plug delivering the power to the srereo - might it be shorting when it gets touched - are you sure the fuse is good immediately before testing and that the act of testing is actually blowing the fuse.

A strange situation - fuse remains good when plugged in to equipment but equipment does not operate - attempts to measure voltage cause fuse to blow. Can you rig up an alternative supply - preferably with a fuse - that bypasses the existing supply route and cable?

Good luck...

Peccavi
July 2010