# Touched battery cables to wrong terminals. Is my radio toast?



## 8v deathsquad (Jan 8, 2005)

In my rush to install a new battery in my 2000 NB, I failed to notice the terminals were opposite of the one I was replacing. I touched the cables to the terminals and got a good spark. 

It burned up one of these little jumps in the fuse box on top of the battery, causing the battery light to come on in the dash. I replaced it with a piece of 12g wire and the light went off. It was actually the one on the ground that burned, but I swapped them around.










It also blew the fuse on the back of my stock head unit, I haven't found any others. But now if I put a new fuse in it immediately blows. Is there something else I'm missing, or did I just ruin my stereo?


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## MyOtherRidesAVette (Nov 13, 2010)

There is a fuse for the radio. Read about another poster who did a similar thing and blew the radio fuse. In his case, he reversed the polarity jumping the car. 

You say you blew the fuse on the ground? The ground isn't fused. Not even a ground wire on that panel. 

Do you mean the black wire on the far left? That is the alternator lead servicing the vehicle. Those aren't "jumps", they are fuses (sometimes refered to as fusible links by old skool ppl), and the fuse you blew was a 110A if you have a 90A alternator, and a 150A if you have a 120A alternator. This fuse may have already been blown, and may be why you thought you needed a new battery in the first place. Why did you think this? When you get everything running you need to have the alternator laod tested AND the voltage regulator checked. Many corner auto parts stores can do this in place. It is not necessary to bench test an alternator and regulator but you do have to have the right equipment. 

I think your 12 AWG wire may be a little light to use for a 110A fuse. That lead services the load reduction relay which services most of your vehicle.

What's up with the fuse in the fourth position from the left? Is that a piece of trash lying on top of it, or is it damaged? That lead services your fuel pump relay (I assume this is not a TDI) and is a 50A.

You have a 10A radio system related fuse in position 37 on your fuse panel (lower section, middle row, bottom fuse), and a 25A in position 42 on the fuse panel (lower section, right row, third from the bottom). I have no clue what the fuse is on the back of your stock HU. I'll have to see if that information is in the Bentley Repair Manual. I think there is a wirring diagram for the HU, is it a base radio or a Monsoon? Not finding any fuse shown in the Bentley on the HU, doesn't mean there isn't one, possibly for the antennae amplifier.

By the way, that poster and I are working through other damage he has apparently done, creating other issues. Possibly electronics damage. 

As an expensive lesson, besides never reversing polarity, here are the other no-no's when it comes to your battery and jump starting. Never allow your car to run off the alternator without a battery hooked up as a shade tree mechanic way of checking your alternator. Never jump start your vehicle with the engine running in the vehicle you are using to jump your vehicle.

You don't say if the car is running, without issues, other than the radio problem.

If you need some more help, you can most easily find me over on the Org. www.newbeetle,org , same User ID. I don't come over here too often, usually checking the NB classifieds when I do.

MORAV


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## 8v deathsquad (Jan 8, 2005)

> Do you mean the black wire on the far left? That is the alternator lead servicing the vehicle. Those aren't "jumps", they are fuses.


Yes that's the one I was referring to. The car sat for about 6 months and the battery wouldn't hold a charge. I'm sure it wasn't blown before because the battery light came on after I reversed the terminals, and when I put the 12 wire on it turned off.



> What's up with the fuse in the fourth position from the left? Is that a piece of trash lying on top of it, or is it damaged? That lead services your fuel pump relay (I assume this is not a TDI) and is a 50A.


Just a little piece of plastic or something sitting on top of it. Engine is a 1.8t.



> You have a 10A radio system related fuse in position 37 on your fuse panel (lower section, middle row, bottom fuse), and a 25A in position 42 on the fuse panel (lower section, right row, third from the bottom). I have no clue what the fuse is on the back of your stock HU


I'll have to double check those fuses tomorrow. The one on the back of the HU is a 10A. The car is running and everything else is working normally.

Thanks for the info it's a good start. :thumbup:


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## MyOtherRidesAVette (Nov 13, 2010)

Okay, I got a little more info out of you. You're correct, the fuse that blew was for the alternator, and the "battery" light came on after the fuse blew because the alternator could not charge anything. FYI, the light has nothing to do with the battery actually, it's what VW calls the "Generator" Light and monitors the output of the alternator.

Now, you say you have a 1.8. My 1.8 has a 120A alternator, if your's does also, that needs to be a 150A fuse, not the 110A you have moved into that position. There should be a label on the alternator visible from the topside. In the meantime, don't operate high draw items like the a/c. You may have to get the steel fuses from VW or online, probably not going to be available at your Corner Auto Parts store.

You need to check all the fuses I have suggested. I'm still at a loss as to the fuse attached to the head unit. Is it a base unit or Monsoon?

Is the car running, battery charging properly, and everything else working properly and without issue?

M.


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## Blingen (Mar 20, 2021)

So ... I did the same thing this morning with my 2012 Jetta... I thought, "That's interesting. Why's it sparking so much? Why's the horn going off?" 
Long story short, The battery light came on, the voltage wasn't right, so I cussed a bit and changed the alternator out - and realized I probably shouldn't have. The voltage is still 12.2 instead of 13+.

What do I check next?


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