Im assuming it is some kind of capacitor? It's labeled L1 and L2 on the PCB. Not sure what L stands for. It appears to be leaking electrolyte and i am assuming it is the reason this device is malfunctioning since it is the first component in series with the V+ pin.

 

If it's labeled "L" then it's an inductor. The capacitors on your board are labeled "Cx". At least I have never seen a capacitor labeled "L".

If it is an inductor it cannot leak anything. Did water get onto this board?

Measure the resistance between the component pins, should be very low.

 

Yes, they are inductors.

I don't recall ever seeing anything leaking from inductors.

hgmjr

 

okay, thank you! yes i believe water got onto the board at some point. although, not recently. the device worked great for a long time then all of a sudden it decided to stop. i say electrolyte but i guess it could be anything. it's a white powdery stuff coming from the bottom of these things

 

so, being an inductor in series with a circuit, do you suppose i could just bypass it momentarily to determine weather or not it is the culprit, or i suppose a simple resistance check at the posts should suffice huh?

 

The inductor nearest your arrow looks like 15uH; the next one is 100uH.
Don't try to operate that dashboard panel without those inductors in place; they are part of the voltage regulation for the board. If you jumper across them and try to operate the board, I guarantee you that you will burn up a switching regulator and/or a MOSFET being used as a switch.

The regulator is depending on the inductors to cause the current to increase at a predictable rate when the switch is turned on. If you jumper across it, the current will increase to maximum with virtually no delay. Besides burning up the switch and/or regulator, you may very well burn up traces on the board and other components that are depending on whatever regulated voltage they are supposed to be receiving.

Did you pull the dash because your gauge needles were not working? That's a GM dash panel, right? And it has small stepper motors driving the needles? Did it come out of a Chevy or GMC truck, like a Silverado or 2500?

 

Very informative! Thank you! This is out of a 01 toyota sequoa. The odometer all of a sudden isn't coming on. Or the speedo or tach. I don't want to buy a new one cause then it won't read the correct mileage. It was working fine a couple weeks ago then the battery died over the last couple weeks (its been parked) when I charged it up it didn't work. Pulled it out and tried another one and the new one worked fine so I know its the cluster. The cluster is all corroded everywhere for some reason but its probably been that way for years.

 

Corrosion doesn't stop once it starts. It keeps right on going until there is nothing left.

Those electrolytic caps with the brown plastic wrapper look like they're REALLY high on the board. Are they corroded out on the bottom? I don't see any electrolyte, but that doesn't mean much. I don't see any glue holding them in place, either. I would think that the leads would break due to metal fatigue with those caps flopping around loose.

If you want to try to get rid of some of that corrosion, clear hand sanitizer works pretty well. You can get jugs of the stuff pretty cheaply. That with an old toothbrush and some elbow grease will help get rid of lots of crud. The nice thing about hand sanitizer is that it evaporates completely, as well as being a pretty good cleaner.

The end of that resistor R49 sure looks corroded, especially right where the lead enters the body of the resistor. I wonder if it's open?

 

Are you near a saltwater coast?

In addition to R49, take a look at the TO-220 mounting screw/rail, and the white specks on the open PCB areas overall.

I'd suggest 1 toothbrush you don't plan on brushing your teeth with again, 1 L Spray bottle, and 1L of 90% Isopropyl alcohol. Put tape over stepper motors so it doesn't get into bearings. Spray and scrub both sides of board until everything is nice and shiny and as clean as possible, and let dry.

It may not ever work again. In that case, it is just an extra expense, buy a new dash panel from www.carpart.com (Finds junkyards in your area). The actual mileage and stuff is stored on your ECU, so swapping out display panels shouldn't be an issue if a good cleaning doesn't fix it, and you aren't familiar with electronics to troubleshoot it.

If that is your dash panel, I'd suggest getting AntiOX or similar compound that prevents water from entering, and applying it to your ECU module and other connectors to keep the nasty stuff out. Many newer cars are coming with that clear goo as a stock item. Be sure to discuss this with your dealer before implementing! They might have a better solution/chemical. Also, the dealer may need to do a reset on the ECU when the new panel is in place, so do the swap in his parking lot, then ask about the protection glue or conformal coatings that may be needed. Tip him a bit if he gives good advice. (anything other than "schedule it to have a new factory dash installed")

 

r49 looks bad but tests fine. i think i'll go ahead with your suggestion of cleaning the whole thing. i've actually got another cluster here from another sequoia, same yr, trim, and all! comparison tests with the dmm show the 101k inductor is fubar'd. as far as the caps are concerned, they are mounted exactly the same as the working cluster i've got.

now, i'd like to order new ones, i'll probably replace both. how should i go about finding a good replacement? i've got the uh rating thanks to wookie but just typing that in gives me all different shapes and sizes, which none look exactly like these ones.

 

Interesting. Did you remove the 100uH inductor from the board?
What are its' dimensions? Height, Diameter, Lead spacing.

Just for show, Digikey has some drum core inductors like these:
http://search.digikey.com/us/en/products/AIRD-02-101K/535-11411-ND/2660672
http://search.digikey.com/us/en/products/AIRD-03-101K/535-11331-ND/2660621
You can compare dimensions to see if it's in the ballpark.

Another possibility is re-winding the original drum core using new magnet wire. Just because it's now open, doesn't necessarily mean that you have to throw it away. You would need to put the same size copper magnet wire back on it, the same number of turns, and use a piece of large-diameter heat shrink tubing to keep the wires in place. It's really not as hard to do as it may sound.

You would need to be very careful when removing the original cover of the inductor; you might even be able to re-use the cover it if it is not full of adhesive or the like. The ferrite drum core is fragile. If you bust it up, you can actually glue it back together - but it's certainly much better if you don't. What will be most helpful about the exercise is to see if it was corrosion or if it was overtemp that caused it to fail. If it was overtemp, you could have a shorted MOSFET switch.

 

Make sure you use the same gauge magnet wire, you may need to order a larger spool. Those inductors are for high current, and the magnet wire Radio Shack sells is neither large enough diameter, or durable enough enameled to survive in an automotive environment.

Both coils should read 0.05Ω-1Ω in resistance, if you are using the inductance feature on a multimeter, you'll need to take them out of circuit.

I'm wondering if the labeling isn't similar to capacitors, except instead of picofarad, the result is μH.

 

The "150" means 15 with no zeros after it; thus 15uH.
The "101" means 10 with one zero after it; thus 100uH.

 

i have to say, i am so impressed with the quality information you guys are providing, much thanks again! so, i ended up removing the inductor from the board and sure enough corrosion had eaten right through the wire connecting the post to the coil. cleaned it up with some hand sanitizer and a tooth brush then dropped a bead in there to bridge the gap, reassembled and installed.......... IT WORKS! thank you all so much!

 

Gee, that's great to know it can be fixed

Careful though - because the solder joint you just made is not nearly as strong as copper. The inductor needs to be secured to the board. A hot glue gun will do a good job of it; if you don't goop too much of it on, you can remove it later if need be.

Leaving just the bit of solder in there is not really a good repair; the magnet wire should not be left with a break in it. Vibration, heating and cooling will work that soft solder until the joint breaks. It's different when the wire is through a hole in the circuit board.