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  #1  
Old 10-16-2017, 03:50 PM
Christopher Murphy Christopher Murphy is offline
 
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Location: colorado
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Default starter selonoid and diode

Today my starter stayed engaged after I released the starter switch. I checked the power lead to the solenoid and the switch was functioning properly. I isolated the solenoid and mechanically jumped the solenoid and the starter continued to turn after I opened the jumper. I then removed the
didode jumper and jumped again and after I opened the jumper the starter motor stopped.

Can failure of the diode jumper cause this? Anyone care to elaborate on the diode jumper that goes from the power coil term to the I term on the solenoid.

thanks

cm
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  #2  
Old 10-16-2017, 04:04 PM
rv7charlie rv7charlie is offline
 
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Default

Lots of starter configurations out there; what have you got? And where's the diode, exactly?
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  #3  
Old 10-16-2017, 04:13 PM
Christopher Murphy Christopher Murphy is offline
 
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Default simple

pretty standard set up

battery wire in and out to starter

starter switch wire to coil terminal..( the one that energizes the relay)

the diode wire was from the above term to the I terminal... according the the early vans instructions that came with the solenoid. the black anoid term on the coil term and the cathode end ( red) on the I terminal..


Seems it should be to ground to me.

cm
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  #4  
Old 10-16-2017, 04:24 PM
PilotjohnS PilotjohnS is offline
 
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Default Diodes do fail

I have seen many diodes fail short. My opinion is if it is critical, use 2 in series. Most people assume diodes are 0.7 v drop, but in reality my experience is that they are typically 0.3 v, so two in series wont hurt anything.JMHO.
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  #5  
Old 10-16-2017, 05:54 PM
bcondrey bcondrey is offline
 
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Default

It sounds like it's wired incorrectly... the "I" terminal has power anytime the starter is engaged. If the diode is between the "S" and "I" terminals then I'd expect exactly what you're seeing. The banded end of the diode should be toward the "S" terminal and the other end should be grounded.
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  #6  
Old 10-16-2017, 06:42 PM
rv7charlie rv7charlie is offline
 
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Default

+1 to what Bob said. A diode on a starter contactor (actually any of the contactors) should be wired across the coil of the contactor. That means from the control terminal (the one that's made hot by the start button) to ground. The banded end goes to the control terminal. Many starter contactors have the ground side of the coil tied to the case of the contactor, which means the other end of the diode would be tied to a mounting screw.
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  #7  
Old 10-16-2017, 06:50 PM
Christopher Murphy Christopher Murphy is offline
 
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Location: colorado
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Default Thanks guys

Bob and Charlie

I thought the same thing. I think its been wrong forever and when the diode failed it energized the coil..

I put it on as directed by the instructions in the packet it came in an ive always thought that was wrong..

Thanks
Cm
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  #8  
Old 10-16-2017, 07:02 PM
bcondrey bcondrey is offline
 
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Default

if you have a 4 post MASTER contactor, the 2 small posts are the coil and and it would be appropriate to put the diode across those terminals (band toward the side connected to the battery).

Starter contactors with 4 posts however are different animals; the coil will have one end grounded through the case and the other end connected to the "S" terminal. You apply power to that terminal to energize (internally connect the large terminals). Some starter contractors have a 4th terminal labeled "I" and it also gets power also when the contactor is energized. Purpose of the optional "I" terminal is to drive a starter mounted solenoid and/or a "starter engaged" light.

It might be that you were reading the instructions for a 4 terminal master contactor rather than a starter contactor...
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  #9  
Old 10-16-2017, 07:16 PM
rv7charlie rv7charlie is offline
 
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Wellll, the I terminal has been repurposed by some aviators for those uses, but the original use was to bypass the ballast resistor in the coil circuit of old style Kettering (breaker points) ignition systems, while the starter operates ("I" terminal...). Kinda tangential to the current discussion, so I'll shut up.
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  #10  
Old 10-16-2017, 07:29 PM
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Tommycat Tommycat is offline
 
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Default Contactor information...

My favorite go to resource about contactors and diodes. HERE... Has pictures!


Regards,
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