Relay has double contacts ???
 

The glow plug relay on my diesel Mercedes, an 83 300SD has two sets of
parallel contacts but only uses one because the other has a gap of about
0.035" when the first set closes. I thought this was due to improper
alignment and I bent the other arm so that both would make contact. The
other day I found another relay and noticed that it had one set of contacts
spaced so they didn't close. Are there any experts out there that can tell
why they do this? My guess is that the open set is a spare for when the
first set wears too much. But that doesn't make sense because two sets
working in parallel wouldn't wear as fast. Also would like to know if
anyone has reversed engineered the circuit as it has an IC and a couple
transistors. The circuit acts as monitor to make sure glow plug no. one is
drawing current and then turns a dash light indicating that the plugs are
heating and when it goes out in a few seconds it OK to hit the starter.
tnx

--

73
Hank WD5JFR

"Henry Kolesnik" schreef in bericht
. com...
The glow plug relay on my diesel Mercedes, an 83 300SD has two sets of
parallel contacts but only uses one because the other has a gap of about
0.035" when the first set closes. I thought this was due to improper
alignment and I bent the other arm so that both would make contact. The
other day I found another relay and noticed that it had one set of
contacts
spaced so they didn't close. Are there any experts out there that can
tell
why they do this? My guess is that the open set is a spare for when the
first set wears too much. But that doesn't make sense because two sets
working in parallel wouldn't wear as fast. Also would like to know if
anyone has reversed engineered the circuit as it has an IC and a couple
transistors. The circuit acts as monitor to make sure glow plug no. one
is
drawing current and then turns a dash light indicating that the plugs are
heating and when it goes out in a few seconds it OK to hit the starter.
tnx

--

Just a weird hunch, maybe the second set is bimetallic? Maybe it closes when
it's very cold; the plugs have to glow longer, and this way the first set is
a bit relieved from the extra (long) load.

Jeroen

They are both part of the same armature and it doesn't look like either one
is bimetallic, just heavy copper

--

73
Hank WD5JFR...
"Jamie" wrote in message
...
Henry Kolesnik wrote:

The glow plug relay on my diesel Mercedes, an 83 300SD has two sets of
parallel contacts but only uses one because the other has a gap of about
0.035" when the first set closes. I thought this was due to improper
alignment and I bent the other arm so that both would make contact. The
other day I found another relay and noticed that it had one set of
contacts spaced so they didn't close. Are there any experts out there
that can tell why they do this? My guess is that the open set is a spare
for when the first set wears too much. But that doesn't make sense
because two sets working in parallel wouldn't wear as fast. Also would
like to know if anyone has reversed engineered the circuit as it has an
IC and a couple transistors. The circuit acts as monitor to make sure
glow plug no. one is drawing current and then turns a dash light
indicating that the plugs are heating and when it goes out in a few
seconds it OK to hit the starter.
tnx

are you sure the other arm isn't some kind of termomatic timer? are they
connected together ?

Henry Kolesnik wrote:
They are both part of the same armature and it doesn't look like either one
is bimetallic, just heavy copper


Hi...

I think you'll find that the relay has two distinct
pull in positions.

The first "gentle" position providing a little heat
required for normal starting; the second providing
far far more during extreme cold weather starts.

Take care.

Ken

No signs of contact wear on the open set...

--

73
Hank WD5JFR
"Ken Weitzel" wrote in message
news:EqnVd.558001$6l.52133@pd7tw2no...


Henry Kolesnik wrote:
They are both part of the same armature and it doesn't look like either
one is bimetallic, just heavy copper


Hi...

I think you'll find that the relay has two distinct
pull in positions.

The first "gentle" position providing a little heat
required for normal starting; the second providing
far far more during extreme cold weather starts.

Take care.

Ken

Henry Kolesnik wrote:

No signs of contact wear on the open set...

Hi...

Can't tell where you live - perhaps you don't
have any of the 30 and 40 below winter weather?

Reason for my suspicion is I've seen here (real cold)
the ignition turned on; voltmeter drops to 9 and a half
or 10 volts... sits there for 20 seconds, then
jumps to about 11 volts for a while...

Makes me pretty sure that there's two levels
available.

Ken

Henry Kolesnik wrote:

The glow plug relay on my diesel Mercedes, an 83 300SD has two sets of
parallel contacts but only uses one because the other has a gap of about
0.035" when the first set closes. I thought this was due to improper
alignment and I bent the other arm so that both would make contact. The
other day I found another relay and noticed that it had one set of contacts
spaced so they didn't close. Are there any experts out there that can tell
why they do this? My guess is that the open set is a spare for when the
first set wears too much. But that doesn't make sense because two sets
working in parallel wouldn't wear as fast. Also would like to know if
anyone has reversed engineered the circuit as it has an IC and a couple
transistors. The circuit acts as monitor to make sure glow plug no. one is
drawing current and then turns a dash light indicating that the plugs are
heating and when it goes out in a few seconds it OK to hit the starter.
tnx

are you sure the other arm isn't some kind of termomatic timer? are they
connected together ?

"Henry Kolesnik" wrote in message
. com...
The glow plug relay on my diesel Mercedes, an 83 300SD has two sets of
parallel contacts but only uses one because the other has a gap of about
0.035" when the first set closes. I thought this was due to improper
alignment and I bent the other arm so that both would make contact. The
other day I found another relay and noticed that it had one set of
contacts
spaced so they didn't close. Are there any experts out there that can
tell
why they do this? ...

No good reason. Are they bifurcated contacts?

N

Henry Kolesnik wrote:

They are both part of the same armature and it doesn't look like either one
is bimetallic, just heavy copper

its very possible that maybe its there for ware.
in other words, as the first one burns away the contacts,
material gets removed, at some point the other side will start contacting.
-------
i have also seen relays being used for Peek and hold effects.
they normally energize a larger solenoid or something.
what happens is when the contacts are closed, the swing load of the
arms will cause the other contact to slam down, giving it a full contact
to deliver full current for a short pulse. then it bounces back and uses
the other side to simply hold it at a lower current state.
but normally those arms are made from some form of clad. giving it a
copper look on the out side but steel in the inside.

I've posted 2 pix to: alt.binaries.schematics.electronic

--

73
Hank WD5JFR

"NSM" wrote in message
news:_IpVd.34389$hN1.24365@clgrps13...

"Henry Kolesnik" wrote in message
. com...
The glow plug relay on my diesel Mercedes, an 83 300SD has two sets of
parallel contacts but only uses one because the other has a gap of about
0.035" when the first set closes. I thought this was due to improper
alignment and I bent the other arm so that both would make contact. The
other day I found another relay and noticed that it had one set of
contacts
spaced so they didn't close. Are there any experts out there that can
tell
why they do this? ...

No good reason. Are they bifurcated contacts?

N

Ken
I live in Tulsa, Oklahoma and it doesn't get that cold here. Each glow
plug has a resistance of less than an ohm and all are wired in parallel and
I can see how the second set of contacts could close and if they did I don't
think the current would increase by that much. The leads going to the glow
plugs look like a little less than No. 12 wire. Someone else asked if the
armature was bifurcated and if we have the same definition for the term it
is bifurcated and stamped out of one piece.

--

73
Hank WD5JFR
"Ken Weitzel" wrote in message
news:gWnVd.557587$8l.65515@pd7tw1no...


Henry Kolesnik wrote:

No signs of contact wear on the open set...

Hi...

Can't tell where you live - perhaps you don't
have any of the 30 and 40 below winter weather?

Reason for my suspicion is I've seen here (real cold)
the ignition turned on; voltmeter drops to 9 and a half
or 10 volts... sits there for 20 seconds, then
jumps to about 11 volts for a while...

Makes me pretty sure that there's two levels
available.

Ken