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why have a relay fitted with resistor ?

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seagull Compulsive Aussie Vee Dubber

4,979 posts · joined Dec 2003 ·

#367397
does it stop back feed ?
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General_Failure Use your head, don't abuse it!

1,036 posts · joined Jun 2004 ·

#367410
Depends on where the resistor is and what it's used for. Can you give us a diagram?
Taking a totally uninformed guess, it may be to stop the source of the switching current being pulled to ground..or it could be an open collec....oh. VW, not electronics. Sorry. Diagram please :P

Anyway, you usually use a capacitor to help with damping spikes and smoothing off abrupt terminations of power. Resistors provide balance to the force :vader
If at first you don't succeed. Build, build again.
Vehicle: 1975 Special order delivery walkthrough panel based LCA pop-top camper. Motor: Nippon 1.8L Single port Wasserboxer, Transmission: 3 rib 002.

bus914 Custom Title Time!

1,230 posts · joined Aug 2002 ·

#367433
Some times they put a multi mega ohm resistor across the relay coil, because it, as coils do, generates a spark when its field collapses. this resistor grounds the spark, while not allowing any significant current flow under normal operating conditions.
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BajaChris Commited Dubber

62 posts · joined Jul 2004 ·

#367469
Are you sure it's not a diode?

I was taught to use diodes for spike suppresion, though I can't think of any reason you would need to use this on a vw
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General_Failure Use your head, don't abuse it!

1,036 posts · joined Jun 2004 ·

#368279
I tend to use capacitors. They soak up all the surging electrons. That's on the main current, not the switching current. Put a cap across the switching pins and it may be a while before your relay turns off.
If at first you don't succeed. Build, build again.
Vehicle: 1975 Special order delivery walkthrough panel based LCA pop-top camper. Motor: Nippon 1.8L Single port Wasserboxer, Transmission: 3 rib 002.

BajaChris Commited Dubber

62 posts · joined Jul 2004 ·

#368565
It's just occured to me that it could be there to prevent radio interference from the switching contacts.
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Purple Martin Fahrvergnugen

913 posts · joined Feb 2003 ·

#368607
BajaChris wrote:It's just occured to me that it could be there to prevent radio interference from the switching contacts.
That would be by damping sparks, wouldn't it? If so, makes sense to me.
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1975 Kombi camper