Park lamp fuse keps blowing

Hi all, I dont know if this is a common problem, but my park lights have suddenly started blowing fuses, I have disconnected all lamps with the exception of the towbar plug and it still blows fuses.
Does this point to the indicator/light/wiper switch?
I cannot unplug the towbar plug as it is stuck hard but I will find a way to disconnect it.
Also I have not disconnected the cluster.
Regards, Tony

Did you change head units or anything recently? The park lamps (pink and blue wires) are on the same circuit as all the backlighting on the dash incl. radio and ventilation controls etc; I'd say you have a short in there somewhere.

Check into bad earths

Thanks guys, I will check both.

You mentioned you've disconnected everything except the towbar plug - well thats the first place I'd be looking

Dion, I did change the head unit recently and cant remember if the park lights worked after that, since its not a daily driver.
I will unplug the head unit tomorrow night to check if that is the cause.
That is the only recent change, so logically it should be the culprit. Or should I say I am the culprit?

My money is on the head unit earthing THROUGH the instrument cluster, vastly increasing the load on the park lamp fuse and blowing it.

Run a separate earth from your head unit to the chassis and your problem should go away.

"You mentioned you've disconnected everything except the towbar plug - well thats the first place I'd be looking"
Exactly, it was the first place I went looking, now if only i could get the wiring plug apart, i would disconnect it.
All I need is some daylight and patience so I dont do more harm than good.

Old.Tony said:

My money is on the head unit earthing THROUGH the instrument cluster, vastly increasing the load on the park lamp fuse and blowing it.

Run a separate earth from your head unit to the chassis and your problem should go away.

Click to expand...

Um, I get the second part, but I'm not sure I understand the first part. How does the head earth through the cluster, and how does that add load to the park lamp? The fuse is between the positive of the battery and the lamp, so even if the head was using the same earth as the cluster, the park lamp fuse wouldn't be drawing any more current, or am I missing something?

Thats what happened with me,what i thought was a negative wire switched too positive when i turned my park lights on, ended up running a seperate wire for the stereo earthing

It's a capacity thing. The stereo doesn't actually draw current on the positive side. The negative side is negative because that's the side electrons come from. The more electrons, the higher the current - which means, the higher the current, the more electrons. Higher energy electrons propagating along a conductor equals higher voltage.

Anyway, if you're earthing the radio through your instrument cluster - the lights from the instrument cluster are fed power from the parkers and hence through the parker fuse - then the current that's going to flow THROUGH that fuse is going to increase.

i found out the hard way when changing my stereo that if i connected the stereo earth to the cars wiring harness earth i would blow my park and dash light fuse. after speaking with an auto electrician he said i would have to earth the stereo to the car not the wiring harness, after doing this no more probs, i didnt think it would make any difference but i was wrong again i think i just like to learn the hard way.

Dion, you were 100% correct, now all working.
Thanks very much to all who offered suggestions.
Tony

DaSmeg said:

Thats what happened with me,what i thought was a negative wire switched too positive when i turned my park lights on, ended up running a seperate wire for the stereo earthing

Click to expand...

I know the problem's sorted and all that, but these sort of things get under my skin, hey. The above post might suggest an alternative reason in some cases.

If the parking lights are positively switched (ie before the lamp), then when the switch is off you might test the wire going from the switch to the lamp, and it would seem like a good earth - resistance of the lamp is quite small and the other end of the lamp is earthed, and is not connected to the 12V while the switch is off.

Meanwhile, the chassis of the head unit butts against the dash frame with enough force to create its own reasonable (but not brilliant) earth connection.

While the parker switch is off, all is fine and dandy. As soon as you turn on your parkers, your new head unit earth wire running to the cluster is actually earthing the parker light fuse through the head unit chassis, rather than the other way around. It wouldn't need to be a brilliant earth to be enough to blow the fuse.

In any case, it always pays to run an earth wire to a good know earth on the chassis.