Relay 109 (m): Replacement for New Car

Hello.

While exploring my car, I also opened up the ubiquitous 109.

What I saw there immediately made me reach for my soldering iron...

ulf wrote:

What I saw there immediately made me turn on my soldering iron.

.... and that's how the vulnerability is actually created.

These crimp connections are extremely temperature-stable, while solder joints are always the worst solution.
I am familiar with stress tests for these connections, and it's quite remarkable what they can withstand without any issues. For comparison, these connections were soldered and subjected to the same tests.
The soldered connections failed after only a few temperature cycles (-40°C to +85°C) under vibration stress, while the clamped connection remained intact.

The reason for these inspections is that during servicing, these crimp connections were re-soldered, and in various vehicles, these re-soldered connections have come loose.

Hello.

While exploring my car, I also opened up the ubiquitous 109.

What I saw there immediately made my soldering iron heat up.

@ulf, but with you, nothing has a chance to remain untouched .


The reason for these investigations was that during the service, these crimp connections were re-soldered, and in various vehicles, these re-soldered connections have come loose.

[irony]
'Something like that definitely doesn't happen with ULF; everything is disassembled after every trip.'
[/ironie]

[irony]

Bertil wrote:

... that during the service, these crimp connections were resoldered, and that in various vehicles, these resoldered connections have come loose.

Hi Bertil,

That's quite something... so, does the "solid" clamping connection fail if it's encased in solder?

Then I will shorten the connector wire slightly and bridge the gap to the contact pin with a loop made of very thin wire, which will absorb temperature and vibration stresses due to its elasticity.

... and put a spare 109 bulb next to the spare light bulbs in the glove compartment .

Best regards,
Uwe

Hi Ulf,

ulf wrote:

... That's quite something... so, does the "solid" clamping connection fail if it's encased in solder? Then I will simply shorten the connector wire a bit and bridge the gap to the contact pin with a loop made of very thin wire, which will absorb temperature and vibration stresses due to its elasticity.

Okay, the solder joint isn't great, but I'd leave it as it is for now. Just keep in mind that if your car ever malfunctions, it might be due to the solder joint. It will probably take several years for the solder joint to completely fail.

These crimp connectors look incredibly fragile, but they are not. You shouldn't repeatedly play with them (opening and closing them), as that's not good for these connections.
In particular, these clamping connections are ideal for applications where connections are exposed to significant temperature and vibration stress, such as in automobiles.

Hello Bertil & all,

Let's take a slight detour into the realm of "development":

Why aren't semiconductor switches used instead of these complex relays?

The 109, with its only 3 connections, practically begs to be replaced, for example, by a transistor, just like the old Lima contact regulators, which have long since become obsolete.

A PNP Darlington switching transistor would be a great alternative to the 109: Connect the emitter to a constant positive voltage, the collector to the load (EDC), and the base to the motor computer's control output via a current-limiting resistor.

If the power transistor is properly saturated, the voltage drop across the switch is less than 0.1 volts, which results in minimal power dissipation.

Are there already FETs or other semiconductor switches available that can switch the load current without any voltage drop?

Something like that would be ideal for a fake AGR signal of the mass airflow sensor .
My engine seems to produce significantly less carbon buildup in the intake manifold compared to the AFN (the ASZ only produces a very light, dry carbon deposit), so I haven't yet made any firm plans to completely disable the EGR system. After almost 2,000 kilometers, I'm still holding off.
But you never know...

ulf wrote:

Why aren't semiconductor switches used instead of these complex relays, which have been around for a long time?

Good question, next please...

I can't tell you that either. Perhaps the semiconductor switches in this power class are still 1 cent too expensive...