[gaminde]

I just looked up smd coding and found a paper that talks about zener's and how there color coded with bands on the ends ??? its too large to upload on this site so a google search is in order.

[Coulomb]

Originally Posted by mora

.. So if that component is missing circuit isn't complete.

Good. So we know it is in series with the negative input lead.

There was no writing on the other side but PCB had silkscreen printing "L2".

Ah. I'd say it's 99% sure that this component is an inductor.

Should I try bridging that component with some wire?

You could do that, but I'd run it from a current limited source like a power supply that you can set the current limit on. I'd start with perhaps a 1 amp limit, even though it might not pull in at that current. There is a good chance that whatever caused L2 to overheat will still be causing way too much current to flow. If the power supply limits itself to a low voltage with 1A flowing continuously, you can say with reasonable certainty that there is still a fault there.

[ Edit: one amp at 12 V is still plenty of power to let smoke out of components. So be very watchful still; don't imagine that the 1 A limit will prevent all possible adverse events, like components burning up. ]

If it all works, [ edit 2: and you don't get a better clue about the value of L2, e.g. by measuring the inductance from a good economizer ] you could do worse than replacing L2 with a surface mount inductor that is capable of handling 3.8 A peak. It looks like a 1515 (4mm x 4mm) component to me, but it's hard to tell from the photo. Any inductance in the range 5 to 50 microhenries would be appropriate, I'd guess. Perhaps less, perhaps down to one microhenry, because of the rather large currents involved.

It will probably work fine with L2 shorted permanently; it's just that a little more of a spike may find its way back into the 12 V circuits that way. But consider that L2 acted as a kind of fuse last time; replacing it with another inductor may prevent worse burning up of components if this sort of thing happens again. It doesn't have to be an accident with a cable; voltage spikes in cars are a fact of life. The inductor will also help protect the economizer circuit from moderate spikes on the 12 V line from elsewhere. (The accidental cable connecting would be considered a jumbo spike .)

[mora]

That was some great info again. I measured resistance from red wire to that other similar looking component. Multimeter reads something like one ohm to both ends of component. Also components resistance seems to be very low. It is hard to tell where tracings go but I'd say that similar component is in series with red wire.

I'll try replacing the broken component with similar sized (physically) inductor.

[gaminde]

So did you try anything yet

[mora]

Nothing yet. I'll try to source that component locally first. I don't want to order full reel of inductors just to try if one of them works for me.

[Coulomb]

Originally Posted by mora

I don't want to order full reel of inductors ...

You should be able to buy a single inductor from the likes of Mouser or Digikey, etc. Freight will cost 10x or 100x the cost of one SMD part, so perhaps buy 10 (for a dollar or two) and have a lifetime supply of spares. There may be a minimum order quantity of 5 or 10 anyway. If the MOQ is something like 1000 or 2000, then just find a similar part number that has a lower MOQ; there will almost certainly be one.

They'll come on a short piece of tape, designed for a pick and place machine, but you can easily peel off the plastic by hand and get them out one component at a time.

[ Edit: re "sourcing locally": there are so many variations of SMD parts (at least 5 main sizes, different maximum currents for inductors, and so on) that usually you can only buy them on-line from companies with large warehouses. There are a few exceptions in my country (Australia), and there may be more in the USA, but I still find it unlikely that you will find an SMD inductor of roughly the right specifications (remember, this one has to withstand the surge current of over 4 A, possibly without saturating) at somewhere "local". Then again, a place like Fry's is pretty big; I haven't been to one recently enough to know what the chances are. ]

[mora]

Yea, I took a look at Digikeys online product index. Now I'll just have to find right one. Or some more with different values and have spares too. Those weren't that pricey anyway.

Local store most likely wouldn't have had anything like this in stock but they will order me anything.

[gaminde]

Originally Posted by mora

Yea, I took a look at Digikeys online product index. Now I'll just have to find right one. Or some more with different values and have spares too. Those weren't that pricey anyway.

Local store most likely wouldn't have had anything like this in stock but they will order me anything.

Well for a test I would get a finish nail and wind my own coil arround it for a nice round coil and then solder it in. Don't spend any money just yet

Oh yea remove the nail when soldering it in its just a form.

[gaminde]

size ohm per 100' ohm per 10'

Solid Wire for
Wire Wrap 30 10.32000 1.03200

[gaminde]

Mora sorry I just cracked myself up at your expense,, I see your from Finland and I said use a (finish nail) this is a real small nail in USA for doing wood trim work.

Coulomb you can use a gator tooth