Radar keeps blowing fuse, cant figure out why

[jbap29]

So a year ago i got a radar using the blendmount mirror tap, which is just two leads that tap into the existing mirror harness, it worked flawlessly for 9 months but recently the radar wasnt powering on and it was because the fuse was blown, replaced fuse, new fuse blew in a day, pulled mirror taps out, reinstalled and it worked for a few days then blew another fuse.

Not a electrical expert so i dont really understand whats going on here. Anyone face the same problems or have any idea whats the deal?

[Smac770]

Something is drawing too much power, or a 12v wire is shorted to the chassis or ground wire.

Is there a plug or something you can disconnect on this radar unit? Disconnect it and see if the fuse stops blowing. It still might if there's a short in the wiring between the v+ and gnd wires.

Don't know anything about the integration solution utilized; I would just troubleshoot it like a normal electrical circuit.

[jbap29]

Something is drawing too much power, or a 12v wire is shorted to the chassis or ground wire.

Is there a plug or something you can disconnect on this radar unit? Disconnect it and see if the fuse stops blowing. It still might if there's a short in the wiring between the v+ and gnd wires.

Don't know anything about the integration solution utilized; I would just troubleshoot it like a normal electrical circuit.

If it was drawing too much power wouldn't it gave blown right away not 9 months later?

It's a power plug from the radar that had two leads on it that you slide into the power mirror harness.

The red and black are the leads that go into the harness. Like I said I'm no expert so I don't really know how to figure out what would be causing the short, everything looks fine so I don't understand.

[A4B7Avant]

I would say the issue is with the radar circuitry itself, not your wiring. Probably a under spec-ed transistor/op amp which slowly deteriorated over the 9 months.

[Smac770]

So the red and black go off to the radar unit? The most logical next step would be to put a multimeter in continuity mode (where it beeps if it detects continuity, ie a short) on the exposed leads there, one probe on exposed black, one probe on exposed red, and see if it registers a short. Maybe the issue is in the plug itself, maybe some plastic is cracked and they are making contact inside.

Something somewhere is now shorted together. You just have to get in there with a meter and see where it beeps when it shouldn't. It could also be an issue that only exposes itself when you try to power on the device, reflecting an internal fault in the device. I don't know anything about current day radar detector products regarding their long term reliability.

[A4B7Avant]

The OP says it takes at least a day to blow, so it isn't a dead short, therefore using meter won't turn up anything wrong.

[jbap29]

The OP says it takes at least a day to blow, so it isn't a dead short, therefore using meter won't turn up anything wrong.

So if it's a short it would blow right away when the car turns on? Bc it's tapped into the mirror so it powers up as soon as the car is started. And I pulled the taps out, reinstalled and then it didn't blow for a couple days.

[Smac770]

Oh, missed that aspect. Still, could be loose wiring shorting together. Might only short when the vehicle is in motion. Put the meter on it and jiggle the wires, press them around, see if it trips. But yeah, could be a heating issue in the device, etc.

[A4B7Avant]

It anything is a dead short the fuse will blow right away or your device will go bang or smoke and/or catch fire.

In you case I would say the fault is component related. Bad voltage regulator, power transistor etc. that overheats with use and then blows the fuse due to excessive current draw fault.

What is the amperage of the fuse recommended?

[1killera4]

It's because Jesus doesn't want you to speed.

[jbap29]

It anything is a dead short the fuse will blow right away or your device will go bang or smoke and/or catch fire.

In you case I would say the fault is component related. Bad voltage regulator, power transistor etc. that overheats with use and then blows the fuse due to excessive current draw fault.

What is the amperage of the fuse recommended?

its 5

yeah im going to contact the radar manufacturer bc it doesnt seem like a short

[jbap29]

It's because Jesus doesn't want you to speed.

then he wouldnt have made fun fast cars

- - - Updated - - -

Oh, missed that aspect. Still, could be loose wiring shorting together. Might only short when the vehicle is in motion. Put the meter on it and jiggle the wires, press them around, see if it trips. But yeah, could be a heating issue in the device, etc.

so if theres no short detected with the meter than its the radar itself thats bad?

[Smac770]

Well, it's either the unit itself drawing excessive current for whatever internal reason, or wires touching. That your fuse doesn't instantly blow every time (no idea if ignition has to be on for it to be powered from that tap) means there's not a short just sitting there all the time. But wires move in a moving car. It's not unheard of for wires to short against something when in motion.

If you really wanted to isolate the device vs the wiring, you'd unplug the device (assuming the wires can be unplugged from it) and mount a ~150kΩ resistor across the plug. Now you've got a static load that produces a constant .1mA current flow (no idea what the specified current draw of that device is) when the circuit is powered. If it shorts again, it's wiring somewhere. If it doesn't short for a week, then it has to be the removed component, the radar unit.

Or test the device by putting it on a 14v power supply with a fuse and let it sit for a week, see if it blows the fuse. But it could be your unit is responding to some input and it drives the current consumption up (because of internal degradation / failure) to the point of blowing the fuse. A static test on a table won't invoke that issue.

In the end, it'll probably be B7's expectation that the device is not robust and starting to fall apart.