Could two relays overload door-unlock output?

[mm]

I have a car alarm, Excalibur, AL-1510-EDP. It has been installed in
my Chryler LeBaron for about 3 years and had always worked fine. (In
a previous car, I had an AL-1000-E for several years)

The alarm included a separate relay to unlock the two doors** and
another separate relay to unlock the trunk. The standard automotive
relays used with car alarms.

Since the trunk lid doesn't pop up anyhow, and I often wanted the
trunk open when I unlocked the car, I changed the wiring, I moved the
trunk relay wire, so that when I unlock the car doors, it also unlocks
the trunk.

Everything was fine for a week, but then the remote, both of them
would no longer arm the alarm, or lock or unlock the locks.**

Did I overload the circuit by connecting two relays to the same
output?

**Alhthough it's not totally dead. I think there are 3 fuses in the
setup and none are blown. When the battery dies (as it did often in
the cold winter, I have a Battery Buddy that disconnects the battery
when it gets too low, and when I push the button on the battery buddy
to reset it, or sometimes after that, when I then turn the ignition
key (one or the other and always), the alarm sounds for 4 or 5 seconds
and stops.


If I overloaded it, or not, is there any chance of repairing it? I
have many years of very part time amateur tv repair. If the problmee
is in an IC, I'm stuck, but if there's an internal relay I overloaded,
I should be able to fix that, for example, and maybe even something
more difficult.



**And another one to look the doors. There is also the other usual
features like a current sensor, a starter motor interrupt, Echo II
two-way remote, plus a regular remote.

 

[Bill]

"mm" wrote in message

I have a car alarm, Excalibur, AL-1510-EDP. It has been installed
in
my Chryler LeBaron for about 3 years and had always worked fine.
(In
a previous car, I had an AL-1000-E for several years)

The alarm included a separate relay to unlock the two doors** and
another separate relay to unlock the trunk. The standard automotive
relays used with car alarms.

Since the trunk lid doesn't pop up anyhow, and I often wanted the
trunk open when I unlocked the car, I changed the wiring, I moved
the
trunk relay wire, so that when I unlock the car doors, it also
unlocks
the trunk.

Everything was fine for a week, but then the remote, both of them
would no longer arm the alarm, or lock or unlock the locks.**

Did I overload the circuit by connecting two relays to the same
output?

**Alhthough it's not totally dead. I think there are 3 fuses in the
setup and none are blown. When the battery dies (as it did often in
the cold winter, I have a Battery Buddy that disconnects the battery
when it gets too low, and when I push the button on the battery
buddy
to reset it, or sometimes after that, when I then turn the ignition
key (one or the other and always), the alarm sounds for 4 or 5
seconds
and stops.


If I overloaded it, or not, is there any chance of repairing it? I
have many years of very part time amateur tv repair. If the
problmee
is in an IC, I'm stuck, but if there's an internal relay I
overloaded,
I should be able to fix that, for example, and maybe even something
more difficult.



**And another one to look the doors. There is also the other usual
features like a current sensor, a starter motor interrupt, Echo II
two-way remote, plus a regular remote.

Usually outputs, like the relays in this case, are sort of a separate
thing which can go bad, but then just the output no longer works, but
everything else works like normal. In technical terms, there would be
a transistor output driving the relay(s) and that, if overloaded,
would act like a fuse and the output only would no longer work.

I suppose an output transistor could fail so that it was always
shorted "on". If that is the case, try powering it up and see if the
relays activate when you power it up. And if this was shorted on, then
it could overload other things in the electronics.

Anyway I would suspect some other problem. Try using a voltmeter to
see if the unit is getting a good 12 volts power.

As to how many relays the output could power, this would be the
amperage rating of the output (transistor or whatever). If you don't
have a schematic diagram of the unit, call the manufacturer and ask.

If you do have schematics, then search for the data sheet for the
output transistor and see the max amperage rating. And also find the
data sheet for the relays and see what their amperage draw is. Here is
an example of a data sheet...
http://www.nxp.com/documents/data_sheet/BUJ105A.pdf

Also relays sometimes have a "flyback diode" which is a backwards
diode. When a relay turns off, it can send a high voltage back into
the electronics and "zap it". That diode prevents this. So it could be
important that you used the provided relays and wired them correctly.

On flyback diodes and relays...
http://www.physics.unlv.edu/~bill/PHYS483/relay.pdf

As to adding the 2nd relay, I would have connected that to the output
of the 1st relay rather than in parallel. Then the alarm output would
only be driving one relay, then that relay would drive the doorlocks
*and* the 2nd relay. Thus you would not be placing an additional
amperage load on that output.

 

[mm]

"mm" wrote in message

Usually outputs, like the relays in this case, are sort of a separate
thing which can go bad, but then just the output no longer works, but
everything else works like normal. In technical terms, there would be
a transistor output driving the relay(s) and that, if overloaded,
would act like a fuse and the output only would no longer work.

That's what I would have thought.

I suppose an output transistor could fail so that it was always
shorted "on". If that is the case, try powering it up and see if the
relays activate when you power it up. And if this was shorted on, then
it could overload other things in the electronics.

Neither the trunk nor the locks do anything when I reconnect, after
the Battery Buddy disconnects (which has happened probably 20+ times).

Anyway I would suspect some other problem. Try using a voltmeter to
see if the unit is getting a good 12 volts power.

But it does set off the siren every time the battery buddy disconnects
the battery and then I reconnect it.

As to how many relays the output could power, this would be the
amperage rating of the output (transistor or whatever). If you don't
have a schematic diagram of the unit, call the manufacturer and ask.

I don't want to bother them just for myself. I'm not a dealer, and I
think they'd prefer me to take it to a dealer or just buy another one.

If you do have schematics, then search for the data sheet for the
output transistor and see the max amperage rating. And also find the
data sheet for the relays and see what their amperage draw is. Here is
an example of a data sheet...
http://www.nxp.com/documents/data_sheet/BUJ105A.pdf

Also relays sometimes have a "flyback diode" which is a backwards
diode. When a relay turns off, it can send a high voltage back into
the electronics and "zap it". That diode prevents this. So it could be
important that you used the provided relays and wired them correctly.

I did put in the diodes, as the installation manual said to.

On flyback diodes and relays...
http://www.physics.unlv.edu/~bill/PHYS483/relay.pdf

I delayed posting until I read these. Thanks.

As to adding the 2nd relay, I would have connected that to the output
of the 1st relay rather than in parallel.

DA

Then the alarm output would

 

[mm]

"mm" wrote in message

Usually outputs, like the relays in this case, are sort of a separate
thing which can go bad, but then just the output no longer works, but
everything else works like normal. In technical terms, there would be
a transistor output driving the relay(s) and that, if overloaded,
would act like a fuse and the output only would no longer work.

That's what I would have thought.

I suppose an output transistor could fail so that it was always
shorted "on". If that is the case, try powering it up and see if the
relays activate when you power it up. And if this was shorted on, then
it could overload other things in the electronics.

Neither the trunk nor the locks do anything when I reconnect, after
the Battery Buddy disconnects (which has happened probably 20+ times).

Anyway I would suspect some other problem. Try using a voltmeter to
see if the unit is getting a good 12 volts power.

But it does set off the siren every time I reconnect after the battery
buddy disconnects, so there must be power.**

As to how many relays the output could power, this would be the
amperage rating of the output (transistor or whatever). If you don't
have a schematic diagram of the unit, call the manufacturer and ask.

I don't want to bother them just for myself. I'm not a dealer, and I
think they'd prefer me to take it to a dealer or just buy another one.

If you do have schematics, then search for the data sheet for the
output transistor and see the max amperage rating. And also find the
data sheet for the relays and see what their amperage draw is. Here is
an example of a data sheet...
http://www.nxp.com/documents/data_sheet/BUJ105A.pdf

Also relays sometimes have a "flyback diode" which is a backwards
diode. When a relay turns off, it can send a high voltage back into
the electronics and "zap it". That diode prevents this. So it could be
important that you used the provided relays and wired them correctly.

I did put in the diodes, as the installation manual said to. I was
careful and I'm sure I did it right, but if they were backwards, that
would cause a problem of its own, from the beginning, right? The
output would be shorted and the locks or trunk would never open, iiuc.

On flyback diodes and relays...
http://www.physics.unlv.edu/~bill/PHYS483/relay.pdf

I delayed posting until I read these. Thanks.

As to adding the 2nd relay, I would have connected that to the output
of the 1st relay rather than in parallel.

DANG! Why didn't I think of that? Better yet, in advance. Then if
it broke, I wouldn't be wondering if I was the cause.

Then the alarm output would
only be driving one relay, then that relay would drive the doorlocks
*and* the 2nd relay. Thus you would not be placing an additional
amperage load on that output.

I have no garage and it was a cold winter. The weather's getting
warm. I'll try some more, I'll open the thing if I have to and check
out the lock output, and if that doesn't work, I'll put in another
one.

Thanks a lot.


**(They don't sell Battery Buddys anymore, but Battery Brains are
simlar. I haven't been stuck by a dead battery in 15 years, since I
got the thing, even though I've used really poor batteries that I know
would have gone completely dead. I love the thing, although I have to
reset the radio stations after it trips, and the engine control
computer forgets details of how to run the engine, but it always seems
fine again within 2 minutes. This is a '95. Maybe newer cars would
forget more.)