Did I fry my car radio? And how can I use a multimeter to troubleshoot?

[suchamoneypit]

So in my infinite wisdom I may have broke a aftermarket car radio.

 

Here's the setup, 2005 Chrysler 300 stock harness correctly adapted to aftermarket radio through an adapter harness thing most aftermarket radios use, however for my red wire 12V constant that activates on ignition, I tapped in a wire for the 12V plug/cigarette lighter (what is even the proper term these days?) Because the stock 12v constant was not strong enough to turn on the radio (common issue with chrylser, Chevy, and jeeps I read)

 

Worked fine besides some other unrelated issues. I took a multimeter and touched a red probe to a metal prong (one at 9 o'clock position of plug) in the 12v power plug and it sparked and the radio shut off and now won't turn back on. Rest of car electrical system fine. 

 

I will inspect it later , but is this just a blown fuse on the radio or did I kill the radio, and if someone could explain the electrical mistake I made and what I made happen so I learn from my mistake , that would be great. 

 

@iamdarkyoshi @CUDAcores89 (you guys seems to be good with this stuff if you got any input please chime in, much appreciated)

 

Also my amp wasn't turning on does anyone know how I can help a multimeter not like a moron in order to test if it's receiving power from the 12V (from battery directly), how to check if my remote on cable is working (sends signal when car radio is turned on telling amp to power on), and also how to check if my ground for the amp is working. 

[AresKrieger]

29 minutes ago, suchamoneypit said:

but is this just a blown fuse on the radio or did I kill the radio, and if someone could explain the electrical mistake I made and what I made happen so I learn from my mistake , that would be great.

So it could easily be a just blown fuse if the fuses are sufficient enough to protect other components, if not it could have burned other components you won't know for sure until you replace any blown fuses present (or see a burnt part on the power line). As for what you likely did I would guess when probing you accidentally hit a ground pin or got too close to a ground pin with the probe on the 12V line, causing an arc and damaging the radio.

 

As for proper probing, I often use hook probes to avoid potential disaster if my hand slips as they can attach to pins. As for ground if you use it as a reference and measure a dc voltage with one probe on it and the other on said DC it should be stable (assuming the dc input is stable) ie not bouncing around by much voltage, a little is fine as the multimeter will fluctuate a little in most cases and a little noise is often present.

 

Another thing to note it is often better to check connectivity while off via impedance measurements rather than measuring voltage if in close proximity to other lines.

[iamdarkyoshi]

Did you have the probes plugged into the current jacks instead of the voltage jacks on the multimeter?

[suchamoneypit]

15 hours ago, Pangea2017 said:

Just replace the blown fuse. They are build for such accidents.

I didn't know if it was a blown fuse or if I broke something. I looked into it today and it was a blown fuse, we are back up and running. 

10 hours ago, iamdarkyoshi said:

Did you have the probes plugged into the current jacks instead of the voltage jacks on the multimeter?

Honestly I'm not sure. It was setup like this. 

[BeefyMeats]

That setting is for measuring resistance, continuity, and amps. So in that mode the probes probably allow current to flow from one probe to the other probe.

A quick search says that meter should only be used to measure a maximum of 200 MICRO amps  a car battery can be like 600amps but the wire in the dash is limited to its own resistance based on the diameter of the wire (so maybe like 40amps though a 12 gauge wire) and hopefully the wire was fused somewhere. 

 

I don't think you would have had trouble if it was in the voltage mode. 

If you want to test continuity to random things, I would suggest sticking the black probe to a known ground, than measuring all your mystery pins for voltage first so nothing gets shorted in the future.

[suchamoneypit]

On 5/2/2018 at 8:41 PM, BeefyMeats said:

That setting is for measuring resistance, continuity, and amps. So in that mode the probes probably allow current to flow from one probe to the other probe.

A quick search says that meter should only be used to measure a maximum of 200 MICRO amps  a car battery can be like 600amps but the wire in the dash is limited to its own resistance based on the diameter of the wire (so maybe like 40amps though a 12 gauge wire) and hopefully the wire was fused somewhere. 

 

I don't think you would have had trouble if it was in the voltage mode. 

If you want to test continuity to random things, I would suggest sticking the black probe to a known ground, than measuring all your mystery pins for voltage first so nothing gets shorted in the future.

I somehow missed your reply, this is extremely informative. Thank you.

[artuc]

So you created a short at the cigarette plug ?

 

Check your accessory fuse, it's probably blown. Stereos also have their own fuses, can check there but it shouldn't have blown. It should be able to tolerate such a fault.

 

Ideally run a new fused constant 12VDC straight from the battery, rated for the current the stereo will draw. You're robbing your current draw from the plug so won't be able to draw a full 10A from it.