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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Relay has double contacts ?? why
"Henry Kolesnik" wrote in message . com... This message was previously posted on alt.auto.mercedes, sci.electronics.components, sci.electronics.repair 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. FWIW, only one set looks like full current contacts. IMO, it may be a relay used for other purposes and they don't want to run current through the light duty points. N |
#2
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No other use than supplying power to the glow plugs, turning a dash lamp on
and off, that's it. -- 73 Hank WD5JFR "NSM" wrote in message news:5bsVd.35599$ab2.22727@edtnps89... "Henry Kolesnik" wrote in message . com... This message was previously posted on alt.auto.mercedes, sci.electronics.components, sci.electronics.repair The glow plug relay on my diesel Mercedes, an 83 300SD has two sets of parallel contacts but only uses one because the other has a gap of about 0.035" when the first set closes. I thought this was due to improper alignment and I bent the other arm so that both would make contact. The other day I found another relay and noticed that it had one set of contacts spaced so they didn't close. Are there any experts out there that can tell why they do this? My guess is that the open set is a spare for when the first set wears too much. But that doesn't make sense because two sets working in parallel wouldn't wear as fast. Also would like to know if anyone has reversed engineered the circuit as it has an IC and a couple transistors. The circuit acts as monitor to make sure glow plug no. one is drawing current and then turns a dash light indicating that the plugs are heating and when it goes out in a few seconds it OK to hit the starter. FWIW, only one set looks like full current contacts. IMO, it may be a relay used for other purposes and they don't want to run current through the light duty points. N |
#3
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There's no other purpose, dash lamp and glow plugs.
-- 73 Hank WD5JFR "NSM" wrote in message news:5bsVd.35599$ab2.22727@edtnps89... "Henry Kolesnik" wrote in message . com... This message was previously posted on alt.auto.mercedes, sci.electronics.components, sci.electronics.repair 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. FWIW, only one set looks like full current contacts. IMO, it may be a relay used for other purposes and they don't want to run current through the light duty points. N |
#4
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"Henry Kolesnik" wrote in message . com... No other use than supplying power to the glow plugs, turning a dash lamp on and off, that's it. This is my best guess. N |
#5
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Sometimes there are two ,where one set takes the first high current ,then
the other set assure there is a true connection. "NSM" wrote in message news:5bsVd.35599$ab2.22727@edtnps89... "Henry Kolesnik" wrote in message . com... This message was previously posted on alt.auto.mercedes, sci.electronics.components, sci.electronics.repair 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. FWIW, only one set looks like full current contacts. IMO, it may be a relay used for other purposes and they don't want to run current through the light duty points. N |
#6
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"Andy" wrote in message ... Sometimes there are two ,where one set takes the first high current ,then the other set assure there is a true connection. The picture doesn't imply this. I suspect they don't want to run current through the second pair. N |
#7
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On Sat, 05 Mar 2005 18:33:32 GMT, "NSM" wrote:
"Andy" wrote in message ... Sometimes there are two ,where one set takes the first high current ,then the other set assure there is a true connection. The picture doesn't imply this. I suspect they don't want to run current through the second pair. N Perhaps the second pair of contacts make a momentary connection during the initial closure, then spring back? ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice480)460-2350 | | | E-mail Address at Website Fax480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
#8
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Jim Thompson wrote:
On Sat, 05 Mar 2005 18:33:32 GMT, "NSM" wrote: "Andy" wrote in message ... Sometimes there are two ,where one set takes the first high current ,then the other set assure there is a true connection. The picture doesn't imply this. I suspect they don't want to run current through the second pair. N Perhaps the second pair of contacts make a momentary connection during the initial closure, then spring back? ...Jim Thompson that is exactly what i suggested also. i have seen that config before used as a peek and hold relay. |
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