Starter Solenoid Questions?

[Scott Zackowski]

Starter Solenoid (not the Solenoid on the Starter) questions?


Background Info: Complete Build, Carbureted, Supplied FFR wiring harness, Breeze supplied Starter Solenoid frame mount type and Mini-Starter kit.

1) I assume the Starter Solenoid large terminals are interchangeable as long as the wires going to each terminal are correct. Clearly the small terminal is for the Lt Blue ignition switch wire. Is that correct?

2) If the Starter Solenoid is not attached to the frame, it must be grounded to the frame via one of the bolts used to attach the Solenoid case. What size/gauge wire should be used to ground it? I wouldn’t think it would need to be a 4-gauge battery type ground or should it?

3) Is there a case to cover the Solenoid? The exposed terminals make me nervous.



Mk IV, Complete Kit, FFR 7304

[DaleG]

What do the instructions say about solenoid wiring? http://www.breezeautomotive.com/details.php?prod_id=490 Have never seen a cover for the solenoid; would be nice, though.

If the solenoid is not attached to frame (not grounded to chassis via the screws) then ground the solenoid to the chassis with ? gauge wire via the G terminal, if there is one. Don't know the proper gauge wire (10, maybe?).

[Scott Zackowski]

Breeze instructions do not specify which Large Terminal. That is what makes me think it does not matter.

[Gumball]

With solenoid facing you, the large terminal on the left is the battery feed. The small terminal on the left is the start signal wire from the ignition switch. The solenoid should be mounted to ground - frame or an aluminum panel that has good ground via the rivets. The right side large terminal goes to the starter and the right side small terminal on the front is for a voltage boost to the coil during "start" if you're using an old-school coil with a resistor wire that only runs 7.5v-9v during run - it gives a boost to 12v when the ignition is turned to "start." If you're running a capacitive discharge (i.e., Pertronix) ignition with a matching coil, then you don't use the small right terminal.

No cover.

[mike w]

26692

[Scott Zackowski]

Great discussion guys!

The Solenoid/Relay I am using is supplied by Breeze and has only three Terminals (2 Large Terminals and 1 Small). See picture below.

It is a Ford Motorcraft part (SW-1951-C or E9TZ-11450-B).

The picture shows my mock-up location. The blue wire is coming from the ignition switch. The 2 gauge cable is representing where the battery feed will connect. The other wires are coming from the FFR wiring harness and are labeled to connect to the Starter Solenoid/Relay. I then plan to connect to the starter with 4 gauge wire from the same terminal as the battery feed. Thus, the line to the starter will always be "hot". The other large terminal (currently empty) will run a 10 gauge wire to the small terminal on the actual Starter's Solenoid.

This is how the Breeze instructions lay it out. The Breeze instructions to not specify which large terminal gets what connected to it as long as the group of connecting wires are correct. Making me believe the large terminal are interchangeable. Seems to make sense now that I understand better how the Solenoid/Relay works.

Also grounding the metal backing to the metal frame with the same gauge as the blue ignition wire makes sense.

Thoughts?

26721

[dforthof]

The ground on a Ford starter solenoid is through the rear mount (like you said), you are correct in thinking that you need to ground the mount of the solenoid out if it is not mounted to a grounded part of the chassis or is mounted to the fiberglass body... luckily, because the ground is only for the control side of the solenoid (not the driven side), 12GA wire is good enough to use between the mount of the solenoid and a good chassis ground, not need to go crazy with 2, 4 or 6 GA becuase the max current on the control side is somewhere in the range of 1-2A. In fact, you're doing yourself a dis-service by using wire > 12GA for the solenoid ground becuse it will propogate an unlikely short within the solenoid if it occurs.

Have fun on your build!!

[Scott Zackowski]

The ground on a Ford starter solenoid is through the rear mount (like you said), you are correct in thinking that you need to ground the mount of the solenoid out if it is not mounted to a grounded part of the chassis or is mounted to the fiberglass body... luckily, because the ground is only for the control side of the solenoid (not the driven side), 12GA wire is good enough to use between the mount of the solenoid and a good chassis ground, not need to go crazy with 2, 4 or 6 GA becuase the max current on the control side is somewhere in the range of 1-2A. In fact, you're doing yourself a dis-service by using wire > 12GA for the solenoid ground becuse it will propogate an unlikely short within the solenoid if it occurs.

Have fun on your build!!

dforthof,

Thanks for the info about the correct wire size/gauge for the ground. I was thinking of using 10 gauge but will now go with 12 gauge.

[Doutie]

Hi Scott,
Dforthof was exactly correct that the winding inside the solenoid will draw 1-2 amps. The winding forms a magnetic field that pulls a plunger with a big cooper washer down onto the two big terminals. So it no more than an electrically operated switch. There's a great site call "The Engineering Toolbox.com" that has all kinds of helpful information. For stranded wire in 12 volt circuits that are not over 10 feet long they give these specs.
18 gauge--4.2 amps
16 gauge--6 amps
14 gauge--9 amps
12gauge-- 12 amps
10 gauge--18 amps
8 gauge--24 amps
6 gauge-- 33 amps
4 gauge-- 42 amps
2 gauge-- 57 amps
Therefore to ground that solenoid an 18 gauge wire would be overkill. Hope this helps, Doutie

[Scott Zackowski]

Hi Scott,
Dforthof was exactly correct that the winding inside the solenoid will draw 1-2 amps. The winding forms a magnetic field that pulls a plunger with a big cooper washer down onto the two big terminals. So it no more than an electrically operated switch. There's a great site call "The Engineering Toolbox.com" that has all kinds of helpful information. For stranded wire in 12 volt circuits that are not over 10 feet long they give these specs.
18 gauge--4.2 amps
16 gauge--6 amps
14 gauge--9 amps
12gauge-- 12 amps
10 gauge--18 amps
8 gauge--24 amps
6 gauge-- 33 amps
4 gauge-- 42 amps
2 gauge-- 57 amps
Therefore to ground that solenoid an 18 gauge wire would be overkill. Hope this helps, Doutie

Doutie,

Thanks for the information and website referral.

[Dan Babb]

Regarding the location you have for mounting it, most guys wind up carpeting that panel on the cockpit side. If you do that, how would you get to the bolt heads that are holding the relay in place?

I guess you could always attach that portion of the carpet with velcro so you could pull it down should you ever need to access it. People have had the relay go bad, so just think about how you'll get it out should you ever need to (especially with the engine in place).

[OCCPete]

If you have a mini starter, you don't need an external solenoid, there's already one on the starter. I understand why people don't remove thier solnoid when upgrading to a mini-starter (you've already got lots of wires attached to the solenoid), but why would you install a solenoid for the solenoid on the initial build?

[Walt]

I am building a basic kit and am almost ready to install drive train, no where in the manual does it say where to install the coil or solenoid.
Any thoughts on where the best place is?
Walt

[DaleG]

Hi Scott,
Dforthof was exactly correct that the winding inside the solenoid will draw 1-2 amps. The winding forms a magnetic field that pulls a plunger with a big cooper washer down onto the two big terminals. So it no more than an electrically operated switch. There's a great site call "The Engineering Toolbox.com" that has all kinds of helpful information. For stranded wire in 12 volt circuits that are not over 10 feet long they give these specs.
18 gauge--4.2 amps
16 gauge--6 amps
14 gauge--9 amps
12gauge-- 12 amps
10 gauge--18 amps
8 gauge--24 amps
6 gauge-- 33 amps
4 gauge-- 42 amps
2 gauge-- 57 amps
Therefore to ground that solenoid an 18 gauge wire would be overkill. Hope this helps, Doutie


Thanks, Wayne. Stuck that treasure away in my Wiring & Electrical folder.

Cheers, Dale