Thin and thick brown wire on solenoid

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nwxh
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Thin and thick brown wire on solenoid

Post by nwxh »

If there is a thick and thin brown wire on the solenoid, is this a sign that the wiring loom is for a dynamo and not an alternator? Is this a case of some old design decision rather than using one thick or two thick wires and should it be upgraded for an alternator?

As far as I see, having two wires, unless a single wire alone can handle the load, is bad as if ones fails there will be no sign until the other wire burns out.
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geoberni
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Re: Thin and thick brown wire on solenoid

Post by geoberni »

What?
If you're referring to the obvious 'thick' battery connection to the solenoid and the thinner brown to the same terminal, that's just a convenient point to connect the car circuits to the battery.
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nwxh
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Re: Thin and thick brown wire on solenoid

Post by nwxh »

Thanks. It's certainly not the cable from the positive terminal but it does attach as a ring underneath that. I now believe that it may not be from the autosparks loom but by the restorer simply to connect the alternator to the solenoid. The other connector (excluding starter motor and key starter) appears I think to connect to a 4 way bullet connector where the control box would be but isn't.

Though I just plan to install a tracker, dash cam and usb port, I guess I should upgrade the route between alternator and battery positive in anticipation of future upgrades like a heated rear windscreen. Though I guess it does have to be two cables to avoid overloading a single spade terminal on the alternator.
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geoberni
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Re: Thin and thick brown wire on solenoid

Post by geoberni »

Best put up a photo, or two, because I'm having trouble understanding what wires you're speaking about.

The Dynamo/Alternator doesn't connect to the Solenoid.... :o
The Solenoid (or Pull Start) only connects between the Battery and the Starter Motor.....

I've looked at the diagrams for late models originally fitted with an Alternator, and because those early Alternators required separate Controllers, the wiring is a bit more intricate, but still no Solenoid connection for the Generator.
I'm not convinced the Manual Wiring Diagram is actually 100% correct for those cars, but never having seen one I have no idea what they actually have. I think there is an erroneous line on the drawing.

But in any case, if I have understood what you've written, we're talking about a car that's been converted from Dynamo with a modern Alternator.
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StillGotMy1stCar
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Re: Thin and thick brown wire on solenoid

Post by StillGotMy1stCar »

I think you have an alternator fitted correctly with this loom.
https://www.morrisminorspares.com/elect ... ng-p829745
As you suggest the two large terminals are joined together within the alternator, I can only think they have used a large and small wire as a cheap way to make up the total current that the alternator can deliver.
Personally I would like to see two wires of the same cross sectional area to share the current equally between the two large alternator terminals.
The alternator output connection to the battery cable side on the solenoid is a common and tidy way of making the connection.

Regards John
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Re: Thin and thick brown wire on solenoid

Post by nwxh »

Image

It is indeed modified to have an alternator. Where would it be best to connect the alternator if I am going to want more upgrades (got a radio somewhere and planning heated rear windows, dashcam usb and and reverse lamp)? Connecting the alternator to a bus bar, then one connection for the equivalent connectors of A/AI where the 4 way bullet connector is, one to the solenoid and then one to any extra fuse box I add?
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Re: Thin and thick brown wire on solenoid

Post by nwxh »

StillGotMy1stCar wrote: Mon May 24, 2021 12:03 am I think you have an alternator fitted correctly with this loom.
https://www.morrisminorspares.com/elect ... ng-p829745
As you suggest the two large terminals are joined together within the alternator, I can only think they have used a large and small wire as a cheap way to make up the total current that the alternator can deliver.
Personally I would like to see two wires of the same cross sectional area to share the current equally between the two large alternator terminals.
The alternator output connection to the battery cable side on the solenoid is a common and tidy way of making the connection.

Regards John
Sorry just saw after replying. I think that has got to be it and perhaps the no point upgrading it if that matches the max output as any short term bursts of using more current such as rear windscreen will have to drain the battery.

It does not seem an ideal design in the first place for there to be two spade connectors on the alternator rather than a single terminal capable of carrying all the current given the danger of one cable going and the other carrying too much.

Many thanks!
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Re: Thin and thick brown wire on solenoid

Post by oliver90owner »

Look up the current specification for that sized spade terminal and compare it to the max current supplied by the alternator. I expect the latter exceeds the former, or the same format is used for higher output alternators.
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Re: Thin and thick brown wire on solenoid

Post by geoberni »

Morning
Now I see the photo, and seen the other comments, I realise you were talking about a couple of 'additional wires' of 2 different sizes, above and beyond the 'Thick' of the Battery Cable. A picture is worth a 1000 words and all that.

Alternators have evolved to have 2 output terminals and they are usually both the same size and are simply a double connection to the actual output. There are of course older ones undoubtedly in use still, with a single output connector.
Some designers on modern cars will use 2 different size cables to split the circuits, so for example the thicker one will include the battery charging connection, while the thinner one will go to things like heated seats and windscreen.
Some moderns will simply use a link at the connector to connect both spade terminals to one output cable, it just depends on the current requirements of the vehicle.

As Oliver said
oliver90owner wrote: Mon May 24, 2021 7:34 am Look up the current specification for that sized spade terminal and compare it to the max current supplied by the alternator. I expect the latter exceeds the former, or the same format is used for higher output alternators.
That's pretty much the reason.
There's a good webpage here explaining the plug/connector differences on early Alternators http://www.mgb-stuff.org.uk/altplug.htm
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Re: Thin and thick brown wire on solenoid

Post by StillGotMy1stCar »

From Berni’s link above.
When I posted just before your photo I assumed you have the Type B alternator with both large terminals joined together as that is the only type I have come across to use that style of plug. :oops:
I now see that it could be the Type A that use the outside large terminal for battery voltage sensing.
The only way to know if it is a Type B is by looking at the connections in the alternator or with a multimeter and test for zero ohms between the large terminals.

Regards John.
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Re: Thin and thick brown wire on solenoid

Post by nwxh »

Hi many thanks again. I found out it's the standard ESM one: https://www.morrisminorspares.com/elect ... le-p829750

Looks like no details on type and capacity.
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Re: Thin and thick brown wire on solenoid

Post by oliver90owner »

Looks like no details on type and capacity.

If you are that worried about it, why not ask ESM directly.

The current carrying capacity for spade terminals is quite well documented on the ‘net if you know where to look. The most common size is likely 8A - a good starting point to compare contact area - but the terminations may well accept a core of certain diameter which will limit the wire connection size.
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Re: Thin and thick brown wire on solenoid

Post by nwxh »

oliver90owner wrote: Fri May 28, 2021 7:22 am Looks like no details on type and capacity.
If you are that worried about it, why not ask ESM directly.
As of yesterday, I am not so worried. The reversing lamp arrived without bulb, but I found an LED bulb which can be fitted with only 42mA draw. Although I'll put wires to the back ready for a heated rear windscreen, that can wait given that the upgrade requires replacing the rear windows.
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