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Just a quick post to give a BIG THANK YOU to IXLR8 for this solution!
On my second day of ownership, my car ('97 993TT) had a DME relay failure (car would crank but not fire up). I replaced the DME relay with the spare that the previous owner had left in the car and the car started right away.
As soon as I came back home, I opened the bad relay and resoldered solder joints. Put that relay back in the car and it started right up
Great tip! Saved myself a new DME, at least for now. I assume they are using leaded solder - not sure how much it even matters but that’s what I have. Back I there now and running great 👍🏼
Bad solder joint on failing DME Post repair. Fingers crossed...
The pictures shows the typical failure of these relays. It gets hot when in use, solder becomes soft, and vibration causes this.
Leaded solder is indeed the way to go, and it will work for another 30 years.
Cheers,
Tore
I've been using a SS relay for over a year now, all good so far. I didn't throw away the electromechanical relay though - it's in the glove box as a spare.
I've been using a SS relay for over a year now, all good so far. I didn't throw away the electromechanical relay though - it's in the glove box as a spare.
Same here. Given the prevalence of comments on this issue seems like cheap insurance to just go to SS and keep the regular one as back up.
I don't know why people think solid state is the way to go. Electronic components fail as well unless you are using military spec components, and yes, those fail too.
Now in a TV, solid state is the way to go. It beats tubes.
Perhaps because us EE's have learned a lot from primitive tech over the last couple decades. While not fail-proof and quality of materials/construction are a consideration, solid state components are generally more reliable.
Perhaps because us EE's have learned a lot from primitive tech over the last couple decades. While not fail-proof and quality of materials/construction are a consideration, solid state components are generally more reliable.
Generally, but having looked at my mechanical relay, once properly soldered, it cannot really fail. I ran current through it and measured the voltage drop across the contacts while cycling the relay over and over when I worked in a lab. It'll last forever. Not worried at all. Hey, but whatever works for users.
Now this doesn't apply to most of us, but when in really remote areas on my motorcycle (as in 152 miles between towns and gas stations), give me gravity feed fuel (no fuel pump), a carb (no fuel infection or pressure regulator) and basic ignition (no Motronic). I can fix that anywhere.
Now if this is "post repair", you missed a few joints, like the ones circled. If I were you, I would take the time to do it right and solder all joints. In fact when I did my board, I de-soldered the old joints, cleaned the pads and applied fresh solder.
And by the way, this is a solder failure, not a component failure. And that can happen on any circuit be it mechanical or solid state.
you missed a few joints, like the ones circled. If I were you, I would take the time to do it right and solder all joints.
And this is a solder failure, not a component failure. And that can happen on any circuit be it mechanical or solid state.
noted, will do, and good eye!
re solid state, everything dies and in fact will usually have some marketed est lifetime value. With SS depending on the technology node it can be quite long. Thermal cycles (how many & how extreme) kill solder joints. The reason I’m not so sure about my repair is that in my experience soldering is fairly nuanced. You need to have the two metal surfaces heated within spec peak temp range for the right duration and have limited contamination for really healthy, robust solder joints. Mine does not appear to have the right look. Good news it it’s easy to identify and re solder on future failure.
semiconductors, on the other hand, predominantly die from heat. E.g. a chip running 27/7 operation at 100C might last >>10ys, while running at 125C could be closer to 3yrs. Chips that go in the tranny, for example must be rated to very high temps. Inside the fuse box (away from the engine compartment) should be under 100C in my black P-car driving through the desert - the devices themselves also generate heat.
Which is why I prefer to work on my own vehicles, aircraft, what have you. You ought to see me on the range but my eyesight is going bad lately.
BTW, all of those solder joints look terrible. Do them all.
Originally Posted by ctilly
semiconductors, on the other hand, predominantly die from heat. E.g. a chip running 27/7 operation at 100C might last >>10ys, while running at 125C could be closer to 3yrs. Chips that go in the tranny, for example must be rated to very high temps.
Spent many years working on the M1A1 computers for the fire control back in the mid to late 80s. Lots of testing, heat cycles, pressure testing, re-work and repeat, etc. after we built them.
05-24-2014, 10:06 AM
