Slow windows, easy first try to improve things

Martin,
Did you see the sparking when the contacts were closing or opening?
Richard

 

Hello Martin,
Glad to see you fixed it, don't know how long it'll last... maybe a long time, as long as it has grease and the touching point were current is driven is wider, not just a small contact point.
Question, what are the contacts made of? Are they soft or hard metal?
I'm asking this because many years ago I had a 300 Liter air compressor with a single phase motor. It started up using a condenser and once rotating it would switch to another condenser via centrifugal contacts. This was the weak point of the motor, contacts would burn out very often. I found that the solution was replacing the contact points for the contacts of ignition points found on any set of points...Tungsten.
It did spark when starting, but didn't burn out.
Just an idea, maybe I'm overkilling the problem.

Best from Spain.

John.
BTW the weather here is really bad now

 

I have found the sparking when opening contacts going to a DC powered coil to be the most destructive due to the flyback effect.
I installed a diode to protect my ignition switch contacts to the starter solenoid.
It is more likely occurring with the window motor coils. I will put flyback diodes in my window circuits.

 

Those switches were only used on the carb cars as I remember. The later ones are much smaller and I do not believe as heavy duty electrically as yours.

Just out of curiosity I looked them up and they seem to be available again.

Nice fix though. The switches were always a common source of voltage loss. Good to know the grease cuts arcing.

 

At least in the 308 era of Ferraris ignition switch failure manifested itself as the plastic parts breaking and jamming the switch. Good part about them though is the electrical portion of the switch is a separate part and not that expensive or hard to change.

 

I have found the sparking when opening contacts going to a DC powered coil to be the most destructive due to the flyback effect.
I installed a diode to protect my ignition switch contacts to the starter solenoid.
It is more likely occurring with the window motor coils. I will put flyback diodes in my window circuits when I open the door panels.

 

The reproductions are junk. That is true. Last time I tried I was able to get SWF? or Bosch for not a lot of money. It was cheap enough I bought a spare or two to put on the shelf.

 

Brian,

New Bosch 308 GTSi 2V Ignition Switches are running in the €200.00+++ range. Ill bet there aint €10 worth of parts in one.

I found a couple NOS for less but I had to literally scower the planet.

 

It has been a couple of years. Not sure what I can get one for now.

 

Good day Richard,

I do not think you will find any benefit from placing a reverse biased diode across the contacts. I say this, as the "sparking" is because of the electric field (e-field) being generated just as the switch contacts start to open. The e-field is inversely proportional to the square of the separation distance between the contacts and so just as the switch contacts open a very, very large e-field is generated which ionizes the air and the spark occurs. Over time this "sparking" causes damage to the contacts. The way to mitigate this and prolong the contacts is to install a "snubber" circuit which is a resistance (could even be 0) in series with a capacitor. Here the Capacitor serves as an energy storage element... a place for the current to flow... as the contacts open far enough such that the e-field drops to a point where it is unable to ionize the air space. This is the reason why a capacitor is used in breaker point ignition systems (and not diodes). A reverse biased diode has other uses, but this would not be where I would use it.

Cheers,

Sam

 

Good day Martin,

Indeed, cleaning the contacts etc will help a lot. Over time oxidation occurs between the contact surfaces which adds resistance. Since the window motors draw a fair amount of current (7+A with a peak of about 11A) the current flowing through these oxidized contacts generates heat. This heat can eventually melt and/or distort the plastic pieces of the switch assembly which eventually can cause a switch failure (does not work, or fail up or down... in my car the switch melted to a permanent on position). Although the newer replacement switches are not made as well as the old ones the fundamental problem is that Ferrari used so-so switches for controlling high load motors... this is a recipe for problems. They should have used the switches to control external relays which would switch the motors. This approach is the best, but cost more because of the extra relays, a bit extra wiring, etc.

In my case I simply designed my own switched relay module in order to preserve the switches, but also to ensure that maximum voltage is seen across the motors... the result is very little current through my switches and so they will last a very long time and my windows move much faster (4 to 6 seconds up or down). Here are some pics of my 365's window switch that failed... this switch is one of the "old" good ones and even it failed because of age and no doubt motor drag (hardened grease, commutator oxidation, etc). Also, a few pics of my relay module... which is quite tiny (about 1.4" x 1.5") that I house in a small plastic enclosure.

Anyway, good job for addressing your switches first. However, I would go to a switched relay approach if you truly wish to minimize issues over time.

Cheers,

Sam

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Very nice, Sam. I did the same thing, but with wires. How big is the PCB? It looks quite compact.

 

The diode does not go between the contacts, Google flyback effect.
You connect the cathode of the diode to the 12 v wire on the motor/coil side and the anode to chassis ground. This will then allow the collapsing field in the coil to go to ground when the flyback effect occurs. This prevents the switch or relay contacts from vaporizing / arcing. Great for extending life of contacts, not ignition points.

 

I fear that poor Martins thread has exploded again. Is there a way to post these great ideas separately but maybe linked by using a very similar title? e.g. "Window Switch Protection - Contact Grease" or "Window Switch Protection - Diode" etc? I love the ideas but am finding it hard to follow.

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Yes Martin. I feel I hijacked your previous thread suggesting latching to reduce operation time.
My Carb car has loads of room for wiring since I removed the 4 cables for the electric mirrors that compressed the grommets for 20 years. [emoji4]. However there's a live feed in the door. Can it not be commoned with any relay feed?
I am going to be going at my 3 switches today with grease as I have doors exposed waiting for my Ganter bump stops (thank you for both ideas).

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Martin, I have copper grease. Awful fluid shiny stuff. Hope this works and I don't break my switches.

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Good day Richard,

No, I understand what you were referring to. However, I disagree that the collapsing field of the motor windings is the primary cause of the sparking. it is true that a reverse voltage is generated by the collapsing motor field, etc, but I believe the fundamental problem is because of the large e-field that is created just as the switch contacts start to open. Switching the window motor (in one direction) is not unlike breaker points and here they use a snubber/capacitor to prolong the point contacts. However, do as you see best.

Cheers,

Sam

 

Tell me more please. I seem to remember way back when I was smart that there is an extreme voltage built up when moving a switch to turn off a circuit, something about racing vehicles and the cuts off switch needing a resistor or diode?

Lester

 

Good day Patrick,

Thank you! Indeed, it is small... around 1.4 x 1.5" However this one is designed for my 365's window motors current characteristics and so a suitable design for the 308 motors could be larger and/or have different relays.

Cheers,

Sam