Solenoid Wiring Problem

[Ray Smith]

I am in the process of replacing the solenoid on my BJ7. I plan on using an after market unit that I have on hand. Can someone tell me the proper way to wire this new unit?

The aftermarket unit has two connection points on the front, one is designated with the letter I, the other is marked with the letter S. Where do I connect the two leads from the starter button to the solenoid? Same for the two leads from the switch.

Thanks,

Ray

 

[Keoke]

Hi Ray, I do not understand how a solenoid with only two connection points on the front can replace one that had Three. I would expect a replacement unit to contain at least three Connection points and possibly four. Similarly, I do not understand why there are two leads coming from the starter button to the solenoid, when usually one is all that is required.---Fwiw--Keoke- /bcforum/images/%%GRAEMLIN_URL%%/confused.gif


Perhaps I should ask why is the solenoid being replaced??

 

[Dave Russell]

The aftermarket unit has two connection points on the front, one is designated with the letter I, the other is marked with the letter S. Where do I connect the two leads from the starter button to the solenoid? Same for the two leads from the switch.
Thanks,
Ray

The solenoid appears to be for a slightly different car. I'm assuming that it has two large terminals & two small terminals. One of the large terminals should go directly to the large cable to the battery. On the same large terminal should be a smaller wire, maybe 12 gage, that goes to the voltage regulator. It is likely brown.

The other large terminal should go to the starter via a large cable.

The small terminal marked "S" should go to the starter button. This wire is likely white/red.

The small terminal marked "I" would be not used. I think it is intended for a system that uses a coil ballast resistor & bypasses the ballast during starting. Not the case with your car.

Your description puzzles me a bit. There should be only one wire from the starter button. I don't understand what you mean by the "two leads from the switch". Would it be the previously mentioned brown & white/red wires?

I don't know if this will help or confuse you.
D

 

[shorn]

Ditto to what Dave wrote. On my BJ8.
A brown wire from the voltage reg. and the heavy gauge wire from the battery connect to one side of the solenoid. Thus the brown wire would always be hot as long as the battery cut off switch is in the on position. The other side with only a heavy gauge wire goes directly to the starter, and is only hot when when the solenoid is activated. Finally the white/red wire from the starter switch is connected to the spade terminal separate from the other wires. The solenoid would be grounded with the bolt connecting it to the chasis. When the starter switch is turned, current from the white red wire activates (closes) the solenoid so that current passes from the heavy gauge battery wire to the heavy gauge starter wire.

 

[Ray Smith]

Dave/Shorn,

Thanks for the explaination. I think that I will be able to install the wires correctly, thanks to your very good description.

How is the starter button grounded if only one wire goes to the solenoid? How does power get from the ignition switch to the distributor?

Thanks,

Ray

 

[shorn]

The power travels through the switch/starter button when it is turned or pushed closing the connection. The grounding occurs at the equipment; i.e. the solenoid. Same thing happens for your lights; the switch closes the connection in the switch supplying power (the hot lead) to your lights, but the grounding or completion of the circuit takes place at the lights themselves. Notice the black wire from your head or. tail lights that goes to the chassis

 

[Dave Russell]

Hi Ray,
The starter button does not get grounded. It supplies voltage to the starter solenoid small terminal marked "S", white/red wire. The solenoid is internally grounded.

There are two white wires on the coil supply side, one from the ignition switch, & one going to other circuits. There are two white/black wires on the other side of the coil, one to the distributor, & one to the battery cut off switch in the back. It grounds the points when the battery switch is turned off.

Some cars used a lower voltage coil, maybe 8 volts, with an external resistor to drop the voltage from 12 volts. The resistor was bypassed by the starter solenoids second small terminal, marked "I", to give full 12 volts to the coil for starting only. As soon as the starter solenoid was released, the resistor was unbypased so that about 8 volts was supplied to the coil while running. Your car does not have a coil resistor, the coil is designed to run on full 12 volts at all times, & so doesn't use this bypass terminal.
D

 

[Keoke]

Well yeah Dave, but the fact that the Healey's installed Lucas solenoid did not include the fourth terminal circumvented ones use of it. However, the ignition system in the car could benefit by its use. There is approximately a 2 volt drop between the starter 12 Volt distribution point and the hot side of the coil during starting. Routing a #16 AWG wire from this fourth terminal to the hot side of the coil would improve cold starting. I have recently found an identical Lucas four terminal solenoid like the one in the Healey located in a box of junk but have not identified is original source as yet. Installed as noted it makes the difference between 10 volts at the coil and more like 11.5.---Fwiw--Keoke

 

[Dave Russell]

Hi Keoke,
Yeah - I suppose there might be some benefit. I've personally never found a need for it. My old car starts first turn with the standard Pertronix ignition & a lowly 31 amp hour battery. Can we mention Miata battery? Plus a GR starter which draws about 1/3 the current of the old starter. Probably over kill.

I haven't really noticed any Healey Sixes either, that particularly needed better starting. I guess if you have starting problems, it might help.

I can't really see a two volt drop from the starter solenoid battery connection point to the coil though. The coil only draws an additional three amps. If the drop was between battery & solenoid, The extra contact wouldn't help unless you went to a lower voltage input coil & ballast resistor.
D

 

[Keoke]

Take a digital Volt meter set it on the 200 volt scale to get rid of the One bit resolution hop so you see a constant voltage and measue it. On a system that is poorly maintained or just old I have measured less than 10 volts at the coil during starting.---Keoke

 

[Dave Russell]

I don't doubt it a bit. Most of the drop is in the battery itself. It wouldn't be unusual for a battery to have .007 ohms internal resistance. At 300 amps starter draw, this resistance would drop the battery voltage by two volts before it ever left the battery. Another 1/2 volt could be dropped in the battery cable, connections, & grounds.

You were saying that an extra wire from a four terminal solenoid would raise the coil voltage. But if the drop is in the battery, adding an extra wire from the solenoid to the coil won't help much.
D
PS - I just measured a very good Optima battery, directly at it's terminals, while starting my truck. The voltage dropped from 12.5 to 10 volts.
D

 

[Keoke]

Dave, Jess get a BJ8 and try it you be surprised! As a matter of fact have you ever noticed that the main #4 battery cable runing underneath the car always has wiggles in it instead of runing straight. well if you watch it while on a lift and crank the engine it will wiggle like a snake. After all for installed chassis wiring applications it is rated at under 200 Amps---Keoke-?

 

[Dave Russell]

Really, BJ8's originally had #4 battery cable? All the ones I've been around have apparently been changed.

That should be entertaining, being under one when starting. Thinking about it, I guess if the current was going on one cable & returning on the frame next to it, things might move.
D