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Can anyone ID this solenoid?

Desert Rat

Well Known Member
I got this in a box of stuff I bought here on VAF a while back. It was sold to me as a start solenoid, presumably since it has 4 posts.

When I started looking at it last night, I realized it's got a jumper from one of the B terminals to what would be the I terminal on a start solenoid.

It's clearly not case grounded.

It doesn't have any markings at all on it other than a couple of inspection stamps on the dome end.

Does anybody have an idea of what I've got here?
 

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It’s just a continuous duty contactor with diodes, typically used as the battery contactor, but you can use it as a starter solenoid.
 
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If I Were A Betting Man ...

I think it's this one - Cole-Hersee #24047 (or equivalent) Intermittent Duty.
This particular contactor (solenoid) has long been used for starter "relay" service.

YMMV - And probably will

HFS

Sorry about the orientation of the pic - still don't know how to rotate them in Doug's format - help? Thx
 

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I think it's this one - Cole-Hersee #24047 (or equivalent) Intermittent Duty.
This particular contractor (solenoid) has long been used for starter "relay" service.

YMMV - And probably will

HFS

Sorry about the orientation of the pic - still don't know how to rotate them in Doug's format - help? Thx

Disagree. Dollars to doughnuts that’s a B&C S701-1 continuous duty contactor with installed spike suppression diode and battery terminal jumper.
 
Intermittent- vs continuous

Get an ammeter and test the activation current for instant and holding. This should allow you to differentiate between the two types. Or use an the ohm function, continuous ~ 15-70+ ohms and starter intermittent ~2-3-4 ohms. Measure it and post.

IIRC (and I may not) the specs are available for the CH solenoids for pull and hold amps. The intermittent (starter) units have a higher current (force) to bang the contacts together for low energy loss in the high amp contacts. The continuous will have lower holding amps so it does not over heat and does not need that high actuation force as the amps are much lower than starting. Also, it could be ok as a relay but not a primary starter solenoid as the instant starting current will reduce service life of the unit, but it could handle the flow through current after closed. Clear as mud?
 
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cole makes both intermittent duty and constant duty versions. If the owner said it was for a starting application, I would be concerned about usiing it as a master, unless you can find a part number on it and confirm it is a constant duty version.

Larry
 
Not sure the brand, but I can tell you my starter solenoid looks identical, same jumper to the main terminal as well as the diode for suppression. The post above from Bill is a good test to tell what it should be used as. MY guess is starter all the way.
 
Yup, don't want to mix up CD with ID solenoids. Using an ID solenoid in place of a CD will put unnecessary draw on the battery. A CD in place of the ID may not be rated for starting current. The Jumper is most likely a grounding diode for reducing arc in the starter switch when contact is broken. The coil in solenoids can produce very high voltages when current flow is interrupted. That's how an ignition coil works. A CD solenoid coil will measure a higher resistance when checked with an OHM meter.

Roberta
 
I got this in a box of stuff I bought here on VAF a while back. It was sold to me as a start solenoid, presumably since it has 4 posts.

When I started looking at it last night, I realized it's got a jumper from one of the B terminals to what would be the I terminal on a start solenoid.

It's clearly not case grounded.

It doesn't have any markings at all on it other than a couple of inspection stamps on the dome end.

Does anybody have an idea of what I've got here?

If it has no pedigree, I'd say use at your own risk. Not sure I would. Could be a genuine Cole Hersee, or could be some piece of junk knock-off. Or worse, like Lucas :).
 
B&C I do not believe makes (manufactures from scratch) contactors (solenoid, relay). They may label or market it as B&C. Their alternators are Nippon Denso, which the "Blue print" and modify. The diode is very common "flyback" voltage spike suppressor. You can roll your own easily or buy a diode kit from Van's (diode with crimp on terminals).

This is BATTERY MASTER contactor, continuous duty. Van sells them (or auto parts or industrial suppliers). Van has a diode kit/ The parts, diode, two crimp terminals are about $1. There are numbers on it? Likely a Cole-Hersee part number, one of typical and most common manufactures.

The STARTER contactor (solenoid) typically has a dark non-matallic body and is intermittent.

Check out Van's store... you will see this. Van covers the diode/terminals in heat shrink. As you all know the diode is a great option. It greatly reduce arching at your switch as the contactor coil EMF collapses and creates big volts. This can reduce the cockpit switches. Arching pits the contacts inside the switch. The Solenoid (relay, contactor) does not care if the diode is there to work.

master
https://store.vansaircraft.com/master-relay-es-24115.html
https://store.vansaircraft.com/surge-protection-diode-for-master-relay-es-diode-master.html

starter
https://store.vansaircraft.com/starter-solenoid-es-24021.html
 
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Terry,

I think that might have even come from my excess parts pile. If so it was a B&C.

Hey Ray- I think you're right. I got it in a box of breakers and switches. Couldn't remember who I got it from.

Now that I think about it, I think that I just saw 4 posts and assumed that it was a starter contactor, until I started looking a little closer.

B&C is just up the road from me. I think I'll ask them what it is the next time I'm up that way
 
A master solenoid typically has the word BATT stamped by one of the main terminals to denote the battery side.
 
What's The "I" Post For ...

on the starter relay Van's sells?

Thx for the help.

HFS
 
The "I" terminal is also used to energize the starter [solenoid] on the PM style starters. This architecture avoids the "hung starter" syndrome sometimes caused by back EMF from the starter motor.
 
I think you got a fair number of suggestions and good methods to figure out what it might be. But in the end there's no good way to know what it actually is.
Personally, without an item # or such stamped on it the only place I'd put it would be the recycle bin. Certainly not an airplane with many expensive things that need to keep the magic smoke contained. ;)
 
A legacy identifier. "I"

Yes "I" is for ignition. Many auto coils were powered with a resistor dropping the voltage from 12 to 6 ish. The I terminal would connect to bypass the resistor during starting, thus providing straight battery voltage. The battery voltage might drop to 9 or 10 v during crank and with the resistor would lower the spark energy substantially.

As stated, measurement of the energizing coil will determine if it is continuous or intermittent. Otherwise donate to some else.
 
Intermittent- vs continuous

Get an ammeter and test the activation current for instant and holding. This should allow you to differentiate between the two types. Or use an the ohm function, continuous ~ 15-70+ ohms and starter intermittent ~2-3-4 ohms. Measure it and post.

IIRC (and I may not) the specs are available for the CH solenoids for pull and hold amps. The intermittent (starter) units have a higher current (force) to bang the contacts together for low energy loss in the high amp contacts. The continuous will have lower holding amps so it does not over heat and does not need that high actuation force as the amps are much lower than starting. Also, it could be ok as a relay but not a primary starter solenoid as the instant starting current will reduce service life of the unit, but it could handle the flow through current after closed. Clear as mud?

An important distinction that Bill makes here: Of course the starting current passes through the master contactor as well as the starter solenoid. But it is already on, and just has to handle that peak current - it does not have to have contacts that can handle the engagement process with that much current.
 
Yup, don't want to mix up CD with ID solenoids. Using an ID solenoid in place of a CD will put unnecessary draw on the battery. A CD in place of the ID may not be rated for starting current. The Jumper is most likely a grounding diode for reducing arc in the starter switch when contact is broken. The coil in solenoids can produce very high voltages when current flow is interrupted. That's how an ignition coil works. A CD solenoid coil will measure a higher resistance when checked with an OHM meter.

Roberta

This has always puzzled me - but then, I'm an aero guy.

An ignition coil works by having two concentric coils. The collapsing field in the primary coil when the current through it is interrupted causes an induced field in the secondary coil, which produces very high voltage (by the ratio of the number of windings in the two coils).

But here we have just a single coil, actuating a pair of contacts by the axial motion of a ferrous rod from the magnetic field in the coil. When the current is interrupted and the field collapses, the rod is pulled back by a spring and opens the contacts. Does the collapsing field induce a high back-voltage in the coil? Does the collapsing field in an ignition coil induce high voltage in the primary coil as well as the secondary coil? I suppose that is why there is always a condenser across the breaker points?
 
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