Dolomite 1300 starter solenoid :Earthing.

[MIG Wielder]

The Dolomite 1300 starter solenoid reminds me of my early Mini ! The question is ... there are 4 terminals. 2 for the high currents in and out, 1 x red/ white for Ignition ballast and a yellow/ white for the ignition key switch.
So when you turn the key to the Start position, 12V will be applied to the white/yellow wire to operate the solenoid. But where is the return path to earth ? Is it through the fixing bolts, meaning you have to keep those clean, or is it like the Sprint / 1850 with the earth connection being made through the low resistance starter motor winding ?
Thank you,
Tony.

[Magenta Auto Sprint]

yes it earths through the mounting flange, just tested mine on the bench.

Malcolm

[MIG Wielder]

Hi Malcolm, Thanks very much for confirming that; It is just as we thought.
Cheers for now,
Tony.

[Larry 1300]

The Dolomite 1300 starter solenoid reminds me of my early Mini ! The question is ... there are 4 terminals. 2 for the high currents in and out, 1 x red/ white for Ignition ballast and a yellow/ white for the ignition key switch.
So when you turn the key to the Start position, 12V will be applied to the white/yellow wire to operate the solenoid. But where is the return path to earth ? Is it through the fixing bolts, meaning you have to keep those clean, or is it like the Sprint / 1850 with the earth connection being made through the low resistance starter motor winding ?
Thank you,
Tony.

Hi could anyone tell me what size the screws are that mount the solenoid to the wing please. So that I can order new ones. Thanks

[MIG Wielder]

Hi Lawrence, The parts book, page 1N 04L, shows the bolts as part no; 513249 with washers WM55. I had a look for these on the www. and drew a blank. So there must be something unusual about them, Like length ? If they go into captive nuts then they will probably be UNF / BSF , If not they will probably be self-tappers.
HTH,
Tony.

[Larry 1300]

Hi thanks for that. I found reference to the page that you mentioned on the internet but got no further than that. Anthony said that they may be self tappers. Laurence

[Carledo]

The parts list pic definitely shows what appears to be parallel thread rather than a tapper and the index, unhelpfully, just calls it a screw. My hazy memory from my Toledo, which shared the remote solenoid before I ripped it all out to fit a Vauxhall motor in 2008, is of setscrews in captive nuts in the flitch, but not the common or garden 1/4" UNF that secure most bits in that area, more like a 3/16" UNF or possibly a BA.

Thinking about it, though the solenoid is long gone, the flitch (and holes) are still there! I'll have a look when the rain eases up!

Steve

[Magenta Auto Sprint]

they may be 10/32 unf or something like that.

malcolm

[Carledo]

OK, i've investigated and it's definitely a captive nut fitting and smaller than 1/4" Whatever it is, it's the same thread as the screws that held the coil in place, just above it on the strut tower. I've searched through my screw collection, garnered from many scrapped Dolomites and easily found a couple of short-ish, new-ish Phillips head setscrews that fit nicely, if somebody wants them!



Steve

[captain_70s]

I did indeed think they were self tappers, but on removal they are a fine thread of some description!

[Magenta Auto Sprint]

A quick summary to small thread sizes:-
U.N.F = Unified National Fine
T.P.I = Threads Per Inch
B.A = British Association


1/4 U.N.F 28 T.P.I Major Diameter 0.250

O B.A 25.4 T.P.I Major diameter 0.236

12/28 U.N.F 28 T.P.I Major Diameter 0.216

10/32 U.N.F 32 T.P.I Major Diameter 0.190

All these screws sizes are available on the internet from various suppliers in stainless steel if required.

Malcolm

[Carledo]

A quick summary to small thread sizes:-
U.N.F = Unified National Fine
T.P.I = Threads Per Inch
B.A = British Association


1/4 U.N.F 28 T.P.I Major Diameter 0.250

O B.A 25.4 T.P.I Major diameter 0.236

12/28 U.N.F 28 T.P.I Major Diameter 0.216

10/32 U.N.F 32 T.P.I Major Diameter 0.190

All these screws sizes are available on the internet from various suppliers in stainless steel if required.

Malcolm

The last 2 of these make no sense Malcolm, 10/32" is better known as 5/16", the common or garden (and misnamed) "half inch bolt", half an inch being the head size across flats. The major diameter of this bolt should be 0.3125", TPI around 24 iirc

The other one makes even less sense, 12/28" translates down to 6/14 and NOBODY measures ANYTHING in fourteenths of an inch!

The screws I have found have a major diameter around 5/32-3/16" ( 0.15625-0.1875", I dont have a vernier caliper to be more precise) and a TPI count of 28-30, the screws are 1/2" long and I get a thread count of 14 or 15 depending on where in the circumference of the screw I count it.

Steve

[Magenta Auto Sprint]

Steve,

Perhaps this will explain this better. I think you mean 3/16 and not 5/16th?

https://journeymans-workshop.uk/unified.php

Malcolm

[Carledo]

Steve,

Perhaps this will explain this better. I think you mean 3/16 and not 5/16th?

https://journeymans-workshop.uk/unified.php

Malcolm

Ah that explains it! 10/32 is not a measurement! My schoolboy fractions, using lowest common denominator, translated 10/32 as 5/16, when in fact it's a NUMBER 10 screw with 32tpi. This also accounts for 12/28.

This makes the screws I have most likely No10 UNF.

Steve

[Larry 1300]

Hi you were spot on with the size of the bolts. Size 10. Thanks