Transmission Destroyed By Python 871xp

Soldered wires can be pulled apart?  This 'test' is rediculous and not based around real world applications.

Here is a test for you:

Take a car with coil on plug ignition.  Cut two trigger wires within 12" of the coil.  Solder one back together and crimp the other.  Drive the car and see which cylinder fails first.  $1000 says its the butt connector EVERY time, IF both are done 'correctly'. 

Butt connectors don't fail due to stress, they fail due to vibration and corrosion.  Your 'weight' test fails to acknowlege this.  Also, how were the wires connected BEFORE soldering?  You should always make a solid mechanical connection (ie twisting) before soldering.  Was this done in the test?  I'm guessing they soldered the wires side by side, and the actual solder joint broke.  Soldering is NOT welding!

Well, you got half the point.

I'm installing a DEI remote start this morning.  Before installation I opened it up and traced out the tach circuit.

There is one component on the input I can't identify (small, brown surface mount) that I believe is a cap.  There is then a 100K resistor going in to an HEF4538BP.  The HEF4538BP is a monostable vibrator - a device used for signal triggering/filtering.  I quit tracing at that chip, and I assume its output goes directly to the processor. 

So, no signs of an opto-isolator, but evidence of a high impedence input.

Are we talking about waterproof (sealed) crimp connectors or the much more commonly found basic blue / YELLOW/red barrel crimp connectors that installers use.  I have NEVER seen an install done with sealed crimp connectors. 

I have also never seen a solder joint corrode.  I've soldered every underhood connection I've ever made and I have never had to repair a single underhood connection because the solder joint failed. 

I'm not sure I follow you about the stress relief.  If you make a good mechanical connection before you solder you will have as good, if not better, strain relief then simply smashing a wire inside a metal crimp connector.

The point about soldering not being welding is that you can not expect solder to bond two wires together.  You must have a good mechanical connection before soldering.  If you simple lay two wries side by side and solder them the connection will most likely fail over time (as you are technically welding here and not soldering). 

I don't mean to get off topic here, but don't VW/Audis have a reputation for terrible electrical systems.  I'm not sure I would put much faith in what their 'engineers' claim.   :)

Anyway, I don't think you can compare a sealed OEM crimp with a field crimp, as they are two completely different things.  OEM crimps are precisely crimped and tested by million+ dollar purpse built machines.  Field crimps are crimped until the person performing the crimp feels that the crimp is sufficient. 

I'm with KP all the way here,let's take this a stage further and end this silly thread because all of the last few entries are right in their own way but:- join wire A from your alarm to wire B in a loom. Cut wire B strip 3/4"/19mm form each end, Strip A 1/4/6.4mm 11/2" from its end wrap one end of B VERY TIGHTLY around the stripped part of a and solder letting the solder flow*  use heat shrink or if under the hood, adhesive lined heatshrink to cover the joint , strip3/4"/19mm from A and WRAP VERY TIGHT around other end of B and solder and sleeve as above. CABLE TIE A to B's loom then cover with insulating tape. I guarantee that joint to last as long as the car because there is no strain at the joint and to me a proper solder joint with no contact resistance will beat every other joint.

2nd point You lot are so lucky not having to work on French and Italien cars, BUT VW and Audi have had ongoing engine management problems for the last 10 years or so, they decided 2 yrs. ago to cut down on their coil plug coil wiring to save money; you guessed it, misfiring cars 1999 onwards M/Benz, Autobox, instead of sep oil cooler rad, lets bury a pipe carrying trannie oil in the rad! Yes the dreaded Mercedes eats its own gearboxes in 2 yrs. syndrome; Bosch alternators, especially on Porsches kill themselves taking the battery with them, 1989 BM 5/7, the electrics had to be redesigned by Bosch; German designed GM (Opel/Vauxhall /Saab) engine bay looms to be redesigned because they were picking up inductive interferance from their alternators, BCM box in R/h kickwell gets waterlogged.

On a reliability track, statistically Clifford and now DEI product is far more reliable than the Space Shuttle, hands on hearts here people, have you EVER had a main unit failure that wasn't down to you?

KPierson wrote:

Anyway, I don't think you can compare a sealed OEM crimp with a field crimp, as they are two completely different things.  OEM crimps are precisely crimped and tested by million+ dollar purpse built machines.  Field crimps are crimped until the person performing the crimp feels that the crimp is sufficient. 

And therein lies the problem. As I mentioned in an earlier post, the crimping tool I use for my professional work to crimp amphenol pins cost around $80 back in the mid-1980s. It is designed to use with one specific size connector and it forces the user to complete the crimping cycle with the proper pressure. One can still mess up the crimped connection, but at least the pin is crimped to the proper level. The crimping tool I use on my automotive work cost $3.95. It works too, but it requires a lot of practice to learn the 'feel' for making a proper crimped connection.

I personally think that properly crimped connectors might be somewhat 'stronger' than soldered connections, but I doubt if those working in typical aftermarket shops invest in the proper crimping tool and many probably haven't developed the skill necessary to perform an adequate job with the cheaper models of crimping tools. I would trust "KPierson" to solder my connections any day and would equally trust "darth tater" to crimp them. For practical purposes in automotive work, the question is not which is ultimtely the best but which is the best for the 'average' (often poorly trained) installer.

So, is it more likely that the average 12-volt automotive installer will make a cold solder joint or an inadequate crimp? Hum, I could see arguements either way. The couple of connections that I saw on my own alarm/remote start installation job showed solder connections perpendicular to the OEM wire with about a 2 or 3 mm solder bead -- certainly not enough to wrap the wire as "KPierson" emphasized is important  for a strong connection (and as I do in my own work).

Finally, as a third-party to the 'soldering isn't welding' discussion (and I don't weld anything except plastic), I agree that this is an important difference. I didn't interpret "KPierson's" comment as a sm'ass interjection. My understanding is that welding (properly done) is real solid, fusing the two metals and soldering on it's best day isn't even close to this level of strength.

FYI: To those who might grumble that this discussion is off topic, this has been one of the more interesting subtopics posted on this thread.

FYI(2): I'm having diffculting posting the the 12-volt; I have to lower my 'shields' (i.e., disable my firewall) for some reason and that prevents quick replies to some of the postings. I'll post my thought sand comments later regarding the main theme of this thread along with occassional remarks regarding subtopics as time permits.

KPierson

I'm installing a DEI remote start this morning.  Before installation I opened it up and traced out the tach circuit.

There is one component on the input I can't identify (small, brown surface mount) that I believe is a cap.  There is then a 100K resistor going in to an HEF4538BP.  The HEF4538BP is a monostable vibrator - a device used for signal triggering/filtering.  I quit tracing at that chip, and I assume its output goes directly to the processor. 

So, no signs of an opto-isolator, but evidence of a high impedence input.

I always appreciate your thoughts and observations, KPierson. But one mans 'high' is another mans, well, not so high. I drive 12-volt signals through 75-125K impedance all the time and don't consider this high. For my brain stimulation work the nominal impendance is around 30K, but we can still deliver precisely regulated DC pulses in the microamp range when the impedance rises, as it often does, to the 100K range. For my work you have to hit the megaohm range before I would consider it a functionally isolated circuit. So, I'm not impressed with the DEI equipment. It's probably adequate for automotive work, but it's way out of range for most scientific work (including the space shuttle).

I haven't pulled the DEI unit out of my vehicle to bench test it yet. I did have to replace the battery in the remote, however. I noticed the day I went to court that the remote had a range of only about 50 yards in an open parking lot (well under the DEI specification) and suspected (hoped) the battery was bad. It was and I tried to open the battery compartment only to have the case split in half at the seam and the circuit board fly out across the floor. The glue they used on the case was weaker than the press-fit on the battery compartment door. Also, note the battery failed after less than 3 months of occasional use (defective, I presume, eh, hope).

I know that DEI never produces a lemon, but gee, I still suspect the unit could be bad. Unfortuantely, neither DEI nor Circuit City would look at it. Perhaps if they did they WOULD have to assume responsibility for my transmission failure.

Finally, it's interesting that the tach wire ties into a monostable vibrator. I told the judge that I suspect that the misconnected wire would have to drive the PCM into an astable mode resulting in oscillation to cause the damage to my transmission. (Remember, the Ford transmission has a fail-safe mode that locks it into 2nd gear if their is an electronics problem.) This was of course above his head (and my M.A. from RPI including coursework in biomedical engineering less 'expertise' than a two-week mail-order certificate that the installer probably even lacked -- OK, that was low, but I am a little psssssd). More on the court case later . . .

Cheers,