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Discussion Starter · #1 ·
OK, I am an electronics tech from 80 or so.

I installed a pair of coils in series, 1 per side, in my Challenger - to 'knock' the highs off midbass - the opposite of a bass blocker, a treble blocker.
Everything tested well sonically, but...
Every once in a while the radio would lock out one of those sides, and tell me "Left Front Open or Short" through OBD. I would reseat radio connector (everything on one) and all would be fine again.
I tried ohming things out, reconnecting everything, etc. a couple of times.
I ran system without series coils for a while - no faults - so not the speaker or amp channel.
Took it all out and redid all, put it back, and the problem moved to the right side.
Apparently I switched sides with the coils.
Now, I'm just inserting a series component's hook up wires into the (cut) factory '+' wires, and soldering everything. I took the coils back out, shook them, beat them as best I could while on an ohmmeter - nothing changed.
I subbed another (3rd) spare coil into the system, problem gone.
For the life of me, I can't figure it out.
If the coil shorted, it would be as though not there at all - series - and not there at all worked fine.
It seems as thought the coil opens - momentarily - and then heals itself. It's wound with good sized (20g?) shellacked wire.
I have no experience with a coil effectively 'opening' to AC, and returning to OK - anyone?

THX guys
 

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The radio is testing the speaker when it is active and the coil at some frequency is representing an open circuit, you are asking the radio to work outside of a set of parameters and it can see something it shouldn’t, it’s not that the coil is actually short just it’s out of the parameters the radio considers ‘normal’
 

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Discussion Starter · #3 ·
Ok, thinking through it...
At some frequency, this coil rises in resistance/reactivity, and just goes past the point where the radio thinks it's OK - say at 5k it goes from 6.9 'Ohms' to 7 and triggers alarm.
I get that, maybe.
Why this 1 out of 3 matching coils? (I really have 4 from JBL crossover bits.)
It's thick wire, on 1 inch plastic air frame, 3 in OD.
Could past life have broken it down - insulation?
Or become passively more or less capacitive when warm?
 

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Maybe put a 20 ohm resister in parallel around the coil?
That will slightly lower the impedence and let a small amount of the freqs through… but it might help the radio to believe that all is well.
 

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Discussion Starter · #5 ·
I had a spare (# 3 of 4 total) just couldn't figure why I couldn't ID a fault in #2.
Looks perfect, ohms just like it's peers, no bad external connection, for some reason this 1 coil trips either side of the radio protection.
 

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The radio is detecting the change in impedance whenever the coil does what you put it there to do. The coil makes the resistance go up in the circuit. This is caused by the impedance rise in the coil.
It's the way coil works. Whenever the system sees something weird with that circuit it gives you the fault. The coil in this case that something weird.
I'm presuming that you wound these yourself? You may have just kinked that one and looked at it funny.
 

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I had a spare (# 3 of 4 total) just couldn't figure why I couldn't ID a fault in #2.
Looks perfect, ohms just like it's peers, no bad external connection, for some reason this 1 coil trips either side of the radio protection.
To find out the difference in that one coil you'd have to test impedance during a frequency sweep with something like DATS or an oscilloscope. You'll never see that with a DMM as they generally only look at 60Hz AC and DC for resistance.

Sent from my SM-G965U using Tapatalk
 
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Discussion Starter · #8 ·
Source - bone stock from old school JBL speakers - removed carefully and wire extended just so.
Instruments - are just home meters and apps...

However, I'm gonna' bet the active impedance on that coil goes up just a hair too much (for reasons unknown) and in #3 suggested by #2.
I was only thinking open and short (as that was the text to the error) but just over a close threshold would almost be logical.
Still would like to know why?
 

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Maybe move the coils around to different channels and see if it tracks the coil?

But it looks likeyou have the answer:

I subbed another (3rd) spare coil into the system, problem gone.
 

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You moved it. The failure followed the component. And, now you replace. Quit worrying about the why since it's intermittent

Temperature and humidity can be blamed when you think that you can't find the problem. Obviously, there is an issue with the coil, when hot or cold, when humid or not, that you can't immediately see. So, don't worry about it and buy a new coil.
 

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Source - bone stock from old school JBL speakers - removed carefully and wire extended just so.
Instruments - are just home meters and apps...

However, I'm gonna' bet the active impedance on that coil goes up just a hair too much (for reasons unknown) and in #3 suggested by #2.
I was only thinking open and short (as that was the text to the error) but just over a close threshold would almost be logical.
Still would like to know why?
You're over-thinking the problem, that one particular coil is falling just outside of the parameters that the head unit tests, the head unit just doesn't like that coil.
 
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