Damaged trace with continuity?

[slidr]

I apologize if this is in the wrong forum, but this is a board from a car so it didn't seem like it belonged anywhere else...

This is a DDM (Driver Door Module) from my gf's 2002 GMC Envoy, i.e. the board under the driver's arm rest panel that controls the windows, locks, heated seats, etc.

These are notorious for being highly susceptible to damage from moisture, so much so, that they issued a recall (just not for this model year). http://www.thecarconnection.com/news...-for-fire-risk

Nothing works on the panel, including the driver's door lock when the remote keyless entry is used (no audible clicks or anything). I swapped the passenger side door module and verified that it does work on the driver's side, so I'm pretty sure that the wires connecting to the board are fine.

Here are some pictures of the only damage I could find on the board.

http://imgur.com/a/3QW1p


I don't have an EMR reader to test the capacitors, but they look ok. I cannot locate a wiring diagram for the car or a diagram for the board, so I'm kind of in the dark.

Any ideas?

1. Is the most likely cause of the failure moisture causing a short between the trace and the area occupied by the two vias, where the other damage appears to be?
   
2. Can the trace still be damaged even though it's only showing 3 ohms of resistance, like most elsewhere on the board?
   
3. Also, where the damage appears to be, what is the point of the two burried vias being there if they appear to be within the same circuit?

Thank you for your help!

[mmartell]

Re: Damaged trace with continuity?

I had one of these from a Chrysler minivan which I could not repair and found a replacement. Mine DID have some broken traces which allowed some led's to function again but nothing beyond that. Did you use a magnifier to check the board or just your eyes ?

Btw, pictures should be posted to the forum using the "Manage Attachments" button.

[mmartell]

Re: Damaged trace with continuity?

What about pins 16 and 15 are they ok ? And 3ohms seems a little high for a trace. What does your dmm read when the probes are touched together ?

[stj]

Re: Damaged trace with continuity?

top right area on the first pic looks like a lot needs re-soldering.

[slidr]

Re: Damaged trace with continuity?

What about pins 16 and 15 are they ok ? And 3ohms seems a little high for a trace. What does your dmm read when the probes are touched together ?

Ha, the same.

And the pins are OK as well.

[slidr]

Re: Damaged trace with continuity?

I had one of these from a Chrysler minivan which I could not repair and found a replacement. Mine DID have some broken traces which allowed some led's to function again but nothing beyond that. Did you use a magnifier to check the board or just your eyes ?

Btw, pictures should be posted to the forum using the "Manage Attachments" button.

Just my eyes. I have a loupe I can use to investigate more. Thanks for the recommendation regarding the pictures.

[slidr]

Re: Damaged trace with continuity?

Ha, the same.

And the pins are OK as well.

EDIT: To clarify, I verified continuity/resistance from those numbered pins to the corresponding pins that would allow me to check that the traces are OK, and they seem to be OK. I also made sure that both ribbons were OK by checking for continuity/resistance at the pins on both sides of the ribbons and they all check out alright.

[slidr]

Re: Damaged trace with continuity?

What about pins 16 and 15 are they ok ? And 3ohms seems a little high for a trace. What does your dmm read when the probes are touched together ?

To clarify my previous response (sorry, I had just taken an Ambien to get to bed), when the probes are touched together, I get 3 Ohms, and get the same when I check any of the traces on the board.

Am I assuming correctly, that the typical resistance of a trace this size on your average board is wayyyyy less than 1 Ohm (wikipedia states that 1 meter of copper wire with 1mm of diameter has 0.02 Ohms of resistance)?

Since my multimeter is unable to measure Ohms at this minuscule level, given the small sizes of most of the components on a circuit board such as this, could a trace be "damaged", but show up as otherwise healthy on my crappy DMM?

Hypothetically, if a healthy trace has 0.02 Ohms of resistance, and this damaged trace has 0.20 Ohms of resistance, would that be enough to "break" the circuit?

I realize the difference is small (0.18) Ohms, but looking at it in another way, that's an increase of 900%!

[mmartell]

Re: Damaged trace with continuity?

Hypothetically i don't know, I'd doubt it but I suppose it could depend on the circuit.

Sounds like your traces are ok and you have other problems. Try taking your meter outside and verify that the ic's are receiving voltage. Maybe there is a fuse on one of those boards ?

[budm]

Re: Damaged trace with continuity?

"wikipedia states that 1 meter of copper wire with 1mm of diameter has 0.02 Ohms of resistance)? Hypothetically, if a healthy trace has 0.02 Ohms of resistance, and this damaged trace has 0.20 Ohms of resistance, would that be enough to "break" the circuit?

I realize the difference is small (0.18) Ohms, but looking at it in another way, that's an increase of 900%!"
But you are dealing with copper trace that you need to know the trace width and the copper thickness to determine the trace resistance.
0.18 Ohms reading is not the problem, you have problem some where else.

[slidr]

Re: Damaged trace with continuity?

If I understand what you are saying, then the trace isn't the problem, but could be related to the problem, in the sense that a component directly connected to the trace could have been overloaded/damaged?

[budm]

Re: Damaged trace with continuity?

That's what it looks like to me, since I do not have the board or info about this board then I cannot tell you what that small trace is connected to. I have seen board that the traces were heated up and the green solder mask were blistered and expose the copper traces.