SL/R129: How many Miles?
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MBWorld Fanatic!
Joined: Jul 2002
Posts: 2,447
Likes: 14
From: UK
SL55 AMG
OK, we're all used to electronics rarely failing, a far cry from 30 years ago when a man used to visit your home to fix the TV.
Electronics in cars is much more challenging than the cosseted environment of a corporate server room and whereas there's an attitude of cost no object in avionics, performance vs value remains an issue in cars.
The things which make electronics a worry in a car like the 129 are:
- Heat, vibration and damp are the enemies of electronics; the failure rate of semiconductors doubles with every 10 degree C rise in temperature. Vibration can lead to broken connections if parts are not mechanically anchored within the electronic module - in other words, it's a mistake to rely on the solder to hold parts in position. Damp leads to corrosion and, if the parts are not perfectly hermetically sealed, incorrect operation. All of these are addressed by putting the electronics in sealed, heat dissipating modules, often in the passenger compartment where the environment is more friendly. For example, in the R230, there's a lot of electronics in the fuse box under the hood, but this is open through the firewall to the passenger compartment.
- the R129 electronics were designed in the late 80s and are not as smart as they are today. That limits things like error logging and diagnostics and means they use parts which are no longer current and may even be in short supply.
- they cannot be repaired. Module replacement is the only answer, there are not the skills and parts available in the field to fix a failing module.
- the modules are made in small numbers, relatively, which makes them very expensive. It's not like the $20 manufacturing cost of an iPod.
So, a 1 cent resistor goes open circuit in your transmission control module. Replacement at several hundred dollars is the only solution.
Chris, I agree the engines are well built, the transmissions too, but as mine showed last year, when they do let go, it's expensive and messy to fix.
Electronics in cars is much more challenging than the cosseted environment of a corporate server room and whereas there's an attitude of cost no object in avionics, performance vs value remains an issue in cars.
The things which make electronics a worry in a car like the 129 are:
- Heat, vibration and damp are the enemies of electronics; the failure rate of semiconductors doubles with every 10 degree C rise in temperature. Vibration can lead to broken connections if parts are not mechanically anchored within the electronic module - in other words, it's a mistake to rely on the solder to hold parts in position. Damp leads to corrosion and, if the parts are not perfectly hermetically sealed, incorrect operation. All of these are addressed by putting the electronics in sealed, heat dissipating modules, often in the passenger compartment where the environment is more friendly. For example, in the R230, there's a lot of electronics in the fuse box under the hood, but this is open through the firewall to the passenger compartment.
- the R129 electronics were designed in the late 80s and are not as smart as they are today. That limits things like error logging and diagnostics and means they use parts which are no longer current and may even be in short supply.
- they cannot be repaired. Module replacement is the only answer, there are not the skills and parts available in the field to fix a failing module.
- the modules are made in small numbers, relatively, which makes them very expensive. It's not like the $20 manufacturing cost of an iPod.
So, a 1 cent resistor goes open circuit in your transmission control module. Replacement at several hundred dollars is the only solution.
Chris, I agree the engines are well built, the transmissions too, but as mine showed last year, when they do let go, it's expensive and messy to fix.
