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

[djdawson2 at aol.com]

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