[urq] High beams/Relays... sigh.

Wed Jun 27 22:22:52 PDT 2012

LOL... taking the time to draw says something.

First, I don't claim to have the electrical knowledge to decipher why the behavior was what it was.  So my conclusions were purely observational.

Second, when this behavior occurred (prior to reversing the polarity) I simply went to the relay and pulled the wire from 85 - and "click" the relay opened, the light went to dim.  I hooked 85 back up, flipped on the brights, and again the one light wouldn't turn off.  Then I pulled the wire to 86, same thing... back to dim.

So, *behaviorally" the relay acted as if current was somehow available, "trapped" or feeding back in a manner that provided the coil sufficient current to keep the 30-87 contact closed.  I was stumped.

Off to the internet... read the bit about polarity, switched the wires, and problem gone.

I can only comment that far, and really nothing more.  I know what the fundamental purpose of a diode is... high resistance in one direction, low in the other, essentially a one-way check valve for current.  I also know that if that diode were not there (or fried), the relay would still function as a relay should... and at that point, polarity could have no possible impact.

I know how a relay works... there aren't many simpler electronic devices out there.

Why this worked or behaved the way it did is a question I can't answer.  However, the solution proposed in the article I read did solve the problem.  The wrong conclusion?  Possibly or probably... didn't really concern me at the time since the issue was resolved.  I bought in.

I wired up those headlights several years ago, but remain reasonably confident that if I were to change the polarity back, I'd experience the same problem.  So...

"The truth is out there"

All I can say is that I'm glad Hackl will have some extra time to discover/fix the bugs in his Pikes Peak steed before the big day.

Dave

-----Original Message-----
From: Scott Justusson <qshipq at aol.com>
To: djdawson2 <djdawson2 at aol.com>; urq <urq at audifans.com>
Sent: Wed, Jun 27, 2012 10:45 pm
Subject: Re: [urq] High beams/Relays... sigh.

Not full of crap, only the possible wrong conclusion?  How bout some Napkins?  Here's how a Bosch/Hella single reverse-bias diode works.  First let's look at a properly hooked up (Pin 86 12v+/Pin 85 12v-) Hella/Bosch single reverse-bias diode relay
http://forums.audiworld.com/picture.php?albumid=166697&pictureid=236800
If you look at C, when switched on, all current flows through the relay coil because the diode blocks current flow through the other parallel path.  If you look at D, switching off your high beams, you get a back EMF load in the opposing polarity.  The diode 'gate' is now open, and the load becomes the actual suppression device (in the form of heating the coil for milliseconds), as apposed to the headlight switch contacts (Note: NOT the pin 30>87 contacts, they have nothing to do with this phenom)

Now, let's take a look at an improper hooked up (Pin 85 12v+/Pin 86 12v-) Hella/Bosch single reverse-bias diode relay
http://forums.audiworld.com/picture.php?albumid=166697&pictureid=236801
If you look at A, when switched on, current flows through both the coil and the relay, the relay will function normally.  If you look at B, this is where the trouble starts.  With the sudden switching off, you get the same back EMF load reverse polarity, but now the diode is blocking that spike.  In the common 1N4001 (standard relay diode app), the Peak Inverse Voltage spike is ~50volts, so chances are good that diode won't last very long until failure. The EMF voltage will now bleed to the headlight switch just before release, and to the board mount (in an electronic circuit).  

What happens when the diode blows in a euro light conversion application?  Nothing. Because it's hooked in parallel, so it's the exact same thing as a non polarized, non diode equipped relay that is used more commonly on the exact same application.  And those of us with non-diode equipped relays running for the last 20 years on our euro-lights installs without a relay or a switch failure can attest that diode doesn't really do anything in a Automotive lighting application.

So.....  What I'm trying to understand is how a diode equipped relay hooked in reverse then, can cause relay sticking.  I claim whatever is going on, the installed *diode* can't cause that, because it's not a possible diode function.  And further, in 'failure' mode, the circuit will operate like any other non diode relay.   And, it's possible I have this very wrong too.....

My apologies in advance to a certain rocket scientist I know out your way, who uses really cool visio programs to draw his circuits, where I prefer the napkin/marker method.....

Cheers

SJ

-----Original Message-----
From: djdawson2 <djdawson2 at aol.com>
To: urq <urq at audifans.com>
Sent: Wed, Jun 27, 2012 8:04 pm
Subject: Re: [urq] High beams/Relays... sigh.

Hmmm... I'll do my best to not take this personally, but seems to me that you're 
telling me I'm full of crap.

My car:
1) 4 brand new Bosch 30 amp relays.
2) Perfectly functioning headlight switch prior to installation.
3) Completed installation resulted in one of my high beams "sticking" on, dash 
indicator did as well.
4) Searched internet, found article claiming that reversed polarity on a diode 
equipped relay could cause relay to remain closed.  Can't comment on the 
validity of this claim, nor can I find it when searching now.  I do not have a 
PhD in electrical engineering.
5) Switched 85 and 86 wires on affected light's relay.
6) Problem solved - NO new stalk installed.

This is a simple statement of fact... it happened on my car.

Initially I believed that there somehow must be voltage remaining between 85 and 
86.  There, in fact, was about 2 volts present (high beams off).

Want me to video this phenom when I get home?

-----Original Message-----
From: Scott Justusson <qshipq at aol.com>
To: mike <mike at urq20v.com>; djdawson2 <djdawson2 at aol.com>; spotatashleys 
<spotatashleys at hotmail.com>; s.b.mills <s.b.mills at gmail.com>; urq 
<urq at audifans.com>
Sent: Wed, Jun 27, 2012 9:03 am
Subject: Re: [urq] High beam indicator stuck on, high beam stalk has no effect- 
what did I break?

I agree Mike!  I have not seen nor heard of a diode affecting 30>87 activation 
in any way, as that's not the purpose/function of the reverse-bias diode.  
Further, although the voltage spike is suppressed, the amperage spike is much 
less 2amps, which is hardly enough to arc weld the points, if they were even 
involved.  Or looked at another way, if the amperage was too high, the coil 
windings would weld themselves together, pretty much eliminating the magnet 
function of the relay.

I say a reverse-bias diode really doesn't do much for a light circuit, nor most 
others basic switched Automotive applications for that matter.  The diode 
protects electronics/switches of components attached to Pin 85 and Pin 86.  It 
is not there for protection of the 30>87 jump.

>From what I read on the internetses, there is more misinformation on what a 
reverse-bias diode equipped relay does, and what it's designed to do.  It's been 
a while since I got trained on them for entry system design, but I don't see a 
big advantage to them in most Automotive applications.  I've run non-diode 
Hella/Bosch relays for years on lights and aux components, and any failures I've 
seen of a 'relay' itself, has nothing to do with, nor would it be 'avoided' by, 
putting diode in the relay.

So much mis-information I read on forums, I was half-tempted to draw out what a 
reverse-bias diode install does in a relay....  From many reads, I bet almost 
half of the reverse-bias diodes are already blown, and the relay is functioning 
just fine.

And btw, I *know* the light switch on the car in question is the problem within 
the first mile of the night-time drive of Steve's car.....

Thanks for the sanity check.  

Scott J

-----Original Message-----
From: Mike Sylvester <mike at urq20v.com>
To: djdawson2 <djdawson2 at aol.com>; qshipq <qshipq at aol.com>; spotatashleys 
<spotatashleys at hotmail.com>; s.b.mills <s.b.mills at gmail.com>; urq 
<urq at audifans.com>
Sent: Wed, Jun 27, 2012 6:56 am
Subject: RE: [urq] High beam indicator stuck on, high beam stalk has no effect- 
what did I break?

First of all, Steve doesn't even have a relay in his circuit so in his
case, the polarity of 85 and 86 is irrelevant.

However, if we want to continue the relay discussion, the wrong polarity
of across 85 and 86 is not going to cause the relay to stick.  For the
high beams to stay on, there needs to be a current path between 30 and
87 or between the positive side of the coil and the load. Its reverse
polarity is not going to create this current path.

The one schematic that I saw had a diode in series with the coil and one
parallel.  The 2 diodes are in opposite directions.  The parallel diode
is to shunt the back emf when the coil gets de-energized. The series
diode is to protect the parallel diode from reverse polarity.  Due to
the series diode, if the 85/86 polarity is reversed, the relay will not
activate when voltage is applied.  Even if the relay does not have the
series diode, a reverse polarity will just cause a lot of current
through the diode, not create a current path to 87.  This high current
could damage your high beam switch.

Regardless, when the high beam switch is off, there shouldn't be a
voltage across the coil circuit, so its polarity wouldn't matter.  If
there is a voltage there, your high beam switch is a problem.

Mike

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