Diode (?) in heater resistor pack
01-02-2005, 11:40 AM
#1
Guest
Posts: n/a
Diode (?) in heater resistor pack
We're working on a friend's "new" 94 Cherokee and have replaced the busted
heater fan motor. We then tracked why the fan only worked on "High" to an
open
component in the heater resistor. It's shown as a switch in the wiring
diagram, and physically resembles a silicon diode. Shorting across it
restored all four fan speeds. Does anyone know what that diode-looking thing
is? And why it's there? I hate to buy a new resistor pack just to replace
the diode (?).
heater fan motor. We then tracked why the fan only worked on "High" to an
open
component in the heater resistor. It's shown as a switch in the wiring
diagram, and physically resembles a silicon diode. Shorting across it
restored all four fan speeds. Does anyone know what that diode-looking thing
is? And why it's there? I hate to buy a new resistor pack just to replace
the diode (?).
01-02-2005, 11:45 AM
#2
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
Diodes only conduct in one direction. So, I'm assuming that the cathode is
pointing towards the motor/fan....if this is the case, then it's there to
prevent the motor from shunting back power to other components back
upstream.
I don't know any other reason for it....not to say there isn't one.
When a motor spins, it has a magnetic/electrical field around it....when the
motor stops, this field collapses and fires current back up the line.
Diodes will help block this....but for different reasons, they stop working.
We just had a problem with a large UPS system at work. When we were
troubleshooting it, we had a large diode blow and send out a 2 foot spark.
Lucky for me, I had a spare pair of drawers in my locker! ;)
Sometimes diodes open....other times they short. BUT, they also weaken
(don't block the way they used to)...but this leads up to one of the first 2
failures.
"Pat Moore" <pmoore@gatecliff.com> wrote in message
news:10tg90dga95ta10@corp.supernews.com...
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking
> thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
>
>
pointing towards the motor/fan....if this is the case, then it's there to
prevent the motor from shunting back power to other components back
upstream.
I don't know any other reason for it....not to say there isn't one.
When a motor spins, it has a magnetic/electrical field around it....when the
motor stops, this field collapses and fires current back up the line.
Diodes will help block this....but for different reasons, they stop working.
We just had a problem with a large UPS system at work. When we were
troubleshooting it, we had a large diode blow and send out a 2 foot spark.
Lucky for me, I had a spare pair of drawers in my locker! ;)
Sometimes diodes open....other times they short. BUT, they also weaken
(don't block the way they used to)...but this leads up to one of the first 2
failures.
"Pat Moore" <pmoore@gatecliff.com> wrote in message
news:10tg90dga95ta10@corp.supernews.com...
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking
> thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
>
>
01-02-2005, 11:45 AM
#3
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
Diodes only conduct in one direction. So, I'm assuming that the cathode is
pointing towards the motor/fan....if this is the case, then it's there to
prevent the motor from shunting back power to other components back
upstream.
I don't know any other reason for it....not to say there isn't one.
When a motor spins, it has a magnetic/electrical field around it....when the
motor stops, this field collapses and fires current back up the line.
Diodes will help block this....but for different reasons, they stop working.
We just had a problem with a large UPS system at work. When we were
troubleshooting it, we had a large diode blow and send out a 2 foot spark.
Lucky for me, I had a spare pair of drawers in my locker! ;)
Sometimes diodes open....other times they short. BUT, they also weaken
(don't block the way they used to)...but this leads up to one of the first 2
failures.
"Pat Moore" <pmoore@gatecliff.com> wrote in message
news:10tg90dga95ta10@corp.supernews.com...
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking
> thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
>
>
pointing towards the motor/fan....if this is the case, then it's there to
prevent the motor from shunting back power to other components back
upstream.
I don't know any other reason for it....not to say there isn't one.
When a motor spins, it has a magnetic/electrical field around it....when the
motor stops, this field collapses and fires current back up the line.
Diodes will help block this....but for different reasons, they stop working.
We just had a problem with a large UPS system at work. When we were
troubleshooting it, we had a large diode blow and send out a 2 foot spark.
Lucky for me, I had a spare pair of drawers in my locker! ;)
Sometimes diodes open....other times they short. BUT, they also weaken
(don't block the way they used to)...but this leads up to one of the first 2
failures.
"Pat Moore" <pmoore@gatecliff.com> wrote in message
news:10tg90dga95ta10@corp.supernews.com...
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking
> thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
>
>
01-02-2005, 11:45 AM
#4
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
Diodes only conduct in one direction. So, I'm assuming that the cathode is
pointing towards the motor/fan....if this is the case, then it's there to
prevent the motor from shunting back power to other components back
upstream.
I don't know any other reason for it....not to say there isn't one.
When a motor spins, it has a magnetic/electrical field around it....when the
motor stops, this field collapses and fires current back up the line.
Diodes will help block this....but for different reasons, they stop working.
We just had a problem with a large UPS system at work. When we were
troubleshooting it, we had a large diode blow and send out a 2 foot spark.
Lucky for me, I had a spare pair of drawers in my locker! ;)
Sometimes diodes open....other times they short. BUT, they also weaken
(don't block the way they used to)...but this leads up to one of the first 2
failures.
"Pat Moore" <pmoore@gatecliff.com> wrote in message
news:10tg90dga95ta10@corp.supernews.com...
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking
> thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
>
>
pointing towards the motor/fan....if this is the case, then it's there to
prevent the motor from shunting back power to other components back
upstream.
I don't know any other reason for it....not to say there isn't one.
When a motor spins, it has a magnetic/electrical field around it....when the
motor stops, this field collapses and fires current back up the line.
Diodes will help block this....but for different reasons, they stop working.
We just had a problem with a large UPS system at work. When we were
troubleshooting it, we had a large diode blow and send out a 2 foot spark.
Lucky for me, I had a spare pair of drawers in my locker! ;)
Sometimes diodes open....other times they short. BUT, they also weaken
(don't block the way they used to)...but this leads up to one of the first 2
failures.
"Pat Moore" <pmoore@gatecliff.com> wrote in message
news:10tg90dga95ta10@corp.supernews.com...
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking
> thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
>
>
01-02-2005, 12:15 PM
#5
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
Pat Moore did pass the time by typing:
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
Any numbers on it or bands?
Can you post a pic of it to alt.binaries.pictures.autos.4x4
or a link?
http://tinyurl.com/465fj
(radioshack)
If it's just a diode you can use any rectifier diode that
is rated high enough for the motor current. Overkill is fine.
276-1661 or 276-1653
However, it could be a different animial. You could be looking
at a thermal fuse designed to turn off the system should the
resistor pack overheat due to a seized motor.
http://www.thermodisc.com/productdet...p?ProductID=30
http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
(lacks pictures)
http://www.circuitspecialists.com/prod.itml/icOid/5704
--
DougW
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
Any numbers on it or bands?
Can you post a pic of it to alt.binaries.pictures.autos.4x4
or a link?
http://tinyurl.com/465fj
(radioshack)
If it's just a diode you can use any rectifier diode that
is rated high enough for the motor current. Overkill is fine.
276-1661 or 276-1653
However, it could be a different animial. You could be looking
at a thermal fuse designed to turn off the system should the
resistor pack overheat due to a seized motor.
http://www.thermodisc.com/productdet...p?ProductID=30
http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
(lacks pictures)
http://www.circuitspecialists.com/prod.itml/icOid/5704
--
DougW
01-02-2005, 12:15 PM
#6
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
Pat Moore did pass the time by typing:
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
Any numbers on it or bands?
Can you post a pic of it to alt.binaries.pictures.autos.4x4
or a link?
http://tinyurl.com/465fj
(radioshack)
If it's just a diode you can use any rectifier diode that
is rated high enough for the motor current. Overkill is fine.
276-1661 or 276-1653
However, it could be a different animial. You could be looking
at a thermal fuse designed to turn off the system should the
resistor pack overheat due to a seized motor.
http://www.thermodisc.com/productdet...p?ProductID=30
http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
(lacks pictures)
http://www.circuitspecialists.com/prod.itml/icOid/5704
--
DougW
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
Any numbers on it or bands?
Can you post a pic of it to alt.binaries.pictures.autos.4x4
or a link?
http://tinyurl.com/465fj
(radioshack)
If it's just a diode you can use any rectifier diode that
is rated high enough for the motor current. Overkill is fine.
276-1661 or 276-1653
However, it could be a different animial. You could be looking
at a thermal fuse designed to turn off the system should the
resistor pack overheat due to a seized motor.
http://www.thermodisc.com/productdet...p?ProductID=30
http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
(lacks pictures)
http://www.circuitspecialists.com/prod.itml/icOid/5704
--
DougW
01-02-2005, 12:15 PM
#7
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
Pat Moore did pass the time by typing:
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
Any numbers on it or bands?
Can you post a pic of it to alt.binaries.pictures.autos.4x4
or a link?
http://tinyurl.com/465fj
(radioshack)
If it's just a diode you can use any rectifier diode that
is rated high enough for the motor current. Overkill is fine.
276-1661 or 276-1653
However, it could be a different animial. You could be looking
at a thermal fuse designed to turn off the system should the
resistor pack overheat due to a seized motor.
http://www.thermodisc.com/productdet...p?ProductID=30
http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
(lacks pictures)
http://www.circuitspecialists.com/prod.itml/icOid/5704
--
DougW
> We're working on a friend's "new" 94 Cherokee and have replaced the busted
> heater fan motor. We then tracked why the fan only worked on "High" to an
> open
> component in the heater resistor. It's shown as a switch in the wiring
> diagram, and physically resembles a silicon diode. Shorting across it
> restored all four fan speeds. Does anyone know what that diode-looking thing
> is? And why it's there? I hate to buy a new resistor pack just to replace
> the diode (?).
Any numbers on it or bands?
Can you post a pic of it to alt.binaries.pictures.autos.4x4
or a link?
http://tinyurl.com/465fj
(radioshack)
If it's just a diode you can use any rectifier diode that
is rated high enough for the motor current. Overkill is fine.
276-1661 or 276-1653
However, it could be a different animial. You could be looking
at a thermal fuse designed to turn off the system should the
resistor pack overheat due to a seized motor.
http://www.thermodisc.com/productdet...p?ProductID=30
http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
(lacks pictures)
http://www.circuitspecialists.com/prod.itml/icOid/5704
--
DougW
01-02-2005, 12:29 PM
#8
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
DougW proclaimed:
> Pat Moore did pass the time by typing:
>
>>We're working on a friend's "new" 94 Cherokee and have replaced the busted
>>heater fan motor. We then tracked why the fan only worked on "High" to an
>>open
>>component in the heater resistor. It's shown as a switch in the wiring
>>diagram, and physically resembles a silicon diode. Shorting across it
>>restored all four fan speeds. Does anyone know what that diode-looking thing
>>is? And why it's there? I hate to buy a new resistor pack just to replace
>>the diode (?).
>
>
> Any numbers on it or bands?
>
> Can you post a pic of it to alt.binaries.pictures.autos.4x4
> or a link?
>
> http://tinyurl.com/465fj
> (radioshack)
>
> If it's just a diode you can use any rectifier diode that
> is rated high enough for the motor current. Overkill is fine.
> 276-1661 or 276-1653
>
> However, it could be a different animial. You could be looking
> at a thermal fuse designed to turn off the system should the
> resistor pack overheat due to a seized motor.
> http://www.thermodisc.com/productdet...p?ProductID=30
> http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
> (lacks pictures)
> http://www.circuitspecialists.com/prod.itml/icOid/5704
>
If it has three leads and looks like a diode otherwise, perhaps a
SCR switch?
> Pat Moore did pass the time by typing:
>
>>We're working on a friend's "new" 94 Cherokee and have replaced the busted
>>heater fan motor. We then tracked why the fan only worked on "High" to an
>>open
>>component in the heater resistor. It's shown as a switch in the wiring
>>diagram, and physically resembles a silicon diode. Shorting across it
>>restored all four fan speeds. Does anyone know what that diode-looking thing
>>is? And why it's there? I hate to buy a new resistor pack just to replace
>>the diode (?).
>
>
> Any numbers on it or bands?
>
> Can you post a pic of it to alt.binaries.pictures.autos.4x4
> or a link?
>
> http://tinyurl.com/465fj
> (radioshack)
>
> If it's just a diode you can use any rectifier diode that
> is rated high enough for the motor current. Overkill is fine.
> 276-1661 or 276-1653
>
> However, it could be a different animial. You could be looking
> at a thermal fuse designed to turn off the system should the
> resistor pack overheat due to a seized motor.
> http://www.thermodisc.com/productdet...p?ProductID=30
> http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
> (lacks pictures)
> http://www.circuitspecialists.com/prod.itml/icOid/5704
>
If it has three leads and looks like a diode otherwise, perhaps a
SCR switch?
01-02-2005, 12:29 PM
#9
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
DougW proclaimed:
> Pat Moore did pass the time by typing:
>
>>We're working on a friend's "new" 94 Cherokee and have replaced the busted
>>heater fan motor. We then tracked why the fan only worked on "High" to an
>>open
>>component in the heater resistor. It's shown as a switch in the wiring
>>diagram, and physically resembles a silicon diode. Shorting across it
>>restored all four fan speeds. Does anyone know what that diode-looking thing
>>is? And why it's there? I hate to buy a new resistor pack just to replace
>>the diode (?).
>
>
> Any numbers on it or bands?
>
> Can you post a pic of it to alt.binaries.pictures.autos.4x4
> or a link?
>
> http://tinyurl.com/465fj
> (radioshack)
>
> If it's just a diode you can use any rectifier diode that
> is rated high enough for the motor current. Overkill is fine.
> 276-1661 or 276-1653
>
> However, it could be a different animial. You could be looking
> at a thermal fuse designed to turn off the system should the
> resistor pack overheat due to a seized motor.
> http://www.thermodisc.com/productdet...p?ProductID=30
> http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
> (lacks pictures)
> http://www.circuitspecialists.com/prod.itml/icOid/5704
>
If it has three leads and looks like a diode otherwise, perhaps a
SCR switch?
> Pat Moore did pass the time by typing:
>
>>We're working on a friend's "new" 94 Cherokee and have replaced the busted
>>heater fan motor. We then tracked why the fan only worked on "High" to an
>>open
>>component in the heater resistor. It's shown as a switch in the wiring
>>diagram, and physically resembles a silicon diode. Shorting across it
>>restored all four fan speeds. Does anyone know what that diode-looking thing
>>is? And why it's there? I hate to buy a new resistor pack just to replace
>>the diode (?).
>
>
> Any numbers on it or bands?
>
> Can you post a pic of it to alt.binaries.pictures.autos.4x4
> or a link?
>
> http://tinyurl.com/465fj
> (radioshack)
>
> If it's just a diode you can use any rectifier diode that
> is rated high enough for the motor current. Overkill is fine.
> 276-1661 or 276-1653
>
> However, it could be a different animial. You could be looking
> at a thermal fuse designed to turn off the system should the
> resistor pack overheat due to a seized motor.
> http://www.thermodisc.com/productdet...p?ProductID=30
> http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
> (lacks pictures)
> http://www.circuitspecialists.com/prod.itml/icOid/5704
>
If it has three leads and looks like a diode otherwise, perhaps a
SCR switch?
01-02-2005, 12:29 PM
#10
Guest
Posts: n/a
Re: Diode (?) in heater resistor pack
DougW proclaimed:
> Pat Moore did pass the time by typing:
>
>>We're working on a friend's "new" 94 Cherokee and have replaced the busted
>>heater fan motor. We then tracked why the fan only worked on "High" to an
>>open
>>component in the heater resistor. It's shown as a switch in the wiring
>>diagram, and physically resembles a silicon diode. Shorting across it
>>restored all four fan speeds. Does anyone know what that diode-looking thing
>>is? And why it's there? I hate to buy a new resistor pack just to replace
>>the diode (?).
>
>
> Any numbers on it or bands?
>
> Can you post a pic of it to alt.binaries.pictures.autos.4x4
> or a link?
>
> http://tinyurl.com/465fj
> (radioshack)
>
> If it's just a diode you can use any rectifier diode that
> is rated high enough for the motor current. Overkill is fine.
> 276-1661 or 276-1653
>
> However, it could be a different animial. You could be looking
> at a thermal fuse designed to turn off the system should the
> resistor pack overheat due to a seized motor.
> http://www.thermodisc.com/productdet...p?ProductID=30
> http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
> (lacks pictures)
> http://www.circuitspecialists.com/prod.itml/icOid/5704
>
If it has three leads and looks like a diode otherwise, perhaps a
SCR switch?
> Pat Moore did pass the time by typing:
>
>>We're working on a friend's "new" 94 Cherokee and have replaced the busted
>>heater fan motor. We then tracked why the fan only worked on "High" to an
>>open
>>component in the heater resistor. It's shown as a switch in the wiring
>>diagram, and physically resembles a silicon diode. Shorting across it
>>restored all four fan speeds. Does anyone know what that diode-looking thing
>>is? And why it's there? I hate to buy a new resistor pack just to replace
>>the diode (?).
>
>
> Any numbers on it or bands?
>
> Can you post a pic of it to alt.binaries.pictures.autos.4x4
> or a link?
>
> http://tinyurl.com/465fj
> (radioshack)
>
> If it's just a diode you can use any rectifier diode that
> is rated high enough for the motor current. Overkill is fine.
> 276-1661 or 276-1653
>
> However, it could be a different animial. You could be looking
> at a thermal fuse designed to turn off the system should the
> resistor pack overheat due to a seized motor.
> http://www.thermodisc.com/productdet...p?ProductID=30
> http://www.partsexpress.com/webpage.cfm?WebPage_ID=63
> (lacks pictures)
> http://www.circuitspecialists.com/prod.itml/icOid/5704
>
If it has three leads and looks like a diode otherwise, perhaps a
SCR switch?