Lotus Elan and Lotus Elan Plus 2 Forums

Could someone please confirm the correct wiring to the starter solenoid on my 1972 +2 S 130/5.
The electrics have the fuses in the centre of the dash and the coil is fitted with a ballast resistor.
Specifically which is the the correct terminal on the solenoid for the White/Yellow (to +ve post on coil) and White/Red (to ignition switch)?
I believe that the White /Red is connected to the lowest, centre right small spade as in the photo and the White/Yellow connected to the left centre spade.
Your clarification would be most welcome please!

Thanks
Gary

My car has White/yellow is middle left, white/red is middle right as viewed on your picture. (The smaller connectors.)

Bottom is 12v from battery and constant power wiring, top is starter motor connection.

Using an ohm meter there should be a lowish ohm reading between the Solenoid activating coil connection and the metal case. This will be one of the smaller terminals. This would be the connection for the wire from the starter position on the ignition switch.

The other small terminal must be the wire to the coil bypassing the ballast resistor.

It probably doesn't matter which of the big terminals you use for the permanent battery connector and hence the other big terminal as the starter motor cable, but those medium size spade connectors go on the permanent battery connection for your fat brown wire to provide unswitched battery voltage to the ignition circuit and the fuses (lights etc).

On our fibre-glass cars don't forget to fit an earthing wire to the case of the solenoid. Without it nothing will happen.

billwill wrote:It probably doesn't matter which of the big terminals you use for the permanent battery connector and hence the other big terminal as the starter motor cable, but those medium size spade connectors go on the permanent battery connection for your fat brown wire to provide unswitched battery voltage to the ignition circuit and the fuses (lights etc).

Not correct,

The ballast by pass comes live at the same time as the starter feed, the small one that has continuity to the large one (should be the large one without the spades on it) is the one you need for ignition feed.

Jon the Chief

oldchieft wrote:

billwill wrote:It probably doesn't matter which of the big terminals you use for the permanent battery connector and hence the other big terminal as the starter motor cable, but those medium size spade connectors go on the permanent battery connection for your fat brown wire to provide unswitched battery voltage to the ignition circuit and the fuses (lights etc).

Not correct,

The ballast by pass comes live at the same time as the starter feed, the small one that has continuity to the large one (should be the large one without the spades on it) is the one you need for ignition feed.

Jon the Chief

Sorry but you are wrong. I think you mis-read my description above.

The starter solenoid is basically the same as a relay. It has a coil, one end of which is connected to ground/Earth and the other end to a terminal (which is not connected to anything else).

The other 3 terminals, two big and one small are isolated initially but all connect together when the coil is activated.

<later>
A pre-engaged starter solenoid has the extra internal coil that you describe creating a connection between the starter switch input terminal and the motor feed big terminal.





~~~~~~~~

It seems that this exact subject has been discussed here before back in 2009
lotus-electrical-f38/starter-solenoid-wiring-t18576.html

Mea Culpa

Yes Bill I am wrong, I metered mine on the car and did not isolate the coil feed.

I metered an old one and it came out as you described and your drawing, so I re-checked the car and it confirmed it.

Thinking it through, it would have to be your way, or the coil feed would earth via the starter.

So as you say it does not matter what side you feed, and what side you connect the load on the big terminals.

Jon the Chief

Slight thread drift...but I have electronic distributor (TT) should the Coil case / bracket be earthed? I haven't earthed mine and although it seems okay...I just wondered.

Thanks all for the replies and the lively debate.

Checked the right side small terminal which was advised to be connected to the ignition switch with white & red wire. As Bill suggested there should be a small resistance to the body/earth. This measured 2.8 ohms on my new solenoid and 3.5 ohms on the 1972 original.

In the +2 workshop manual Fig. 80 there is a white / yellow wire shown to the ballast which is slightly different to Bill's image. For the later +2, the white/yellow from the left of the solenoid (live during cranking only) connects to the +ve on the coil where in Fig. 80 this link is white/blue.

Anyway, all clear now and I can progress in confidence......!

Gary

The picture of the solenoid with the wire colours shown, is not actually one of mine
it comes from the other thread mentioned above.

Bill

Don't know what the circuit diagram is that you have uploaded but its not of a Lucas as Fitted to our +2s.
There is only one coil circuit and you can use either large stud for battery supply/starter.
To my knowledge as you look at the photo of the unit that was uploaded by Gary, is as follows

North and south large studs are battery supply and starter either way
West is ballast bypass.
East is solenoid supply.

Early solenoid units had a smaller spade for the ballast supply to indicate it

Hawksfield wrote:Bill

Don't know what the circuit diagram is that you have uploaded but its not of a Lucas as Fitted to our +2s.
There is only one coil circuit and you can use either large stud for battery supply/starter.
To my knowledge as you look at the photo of the unit that was uploaded by Gary, is as follows

North and south large studs are battery supply and starter either way
West is ballast bypass.
East is solenoid supply.

Early solenoid units had a smaller spade for the ballast supply to indicate it

You didn't read my text accurately Your text re-iterates what I actually said.
The diagram with the double internal coil is for a solenoid of a pre-engaged motor

I didn't put up a circuit diagram of our bulkhead solenoids as I couldn't find a good one with the ballast connector.

Hawksfield wrote:Bill

North and south large studs are battery supply and starter either way
West is ballast bypass.
East is solenoid supply.

Early solenoid units had a smaller spade for the ballast supply to indicate it

Some units have a different terminals for the ignition feeds, some Ford had a threaded stud other makes have a male for the solenoid operation an a female for the ballast by pass.

Jon the Chief

Bill

Your quite right