33 replies to this topic

[Ethel]

The diode would go between where the the feed to operate the solenoid is tapped off and the alternator.

 

 

^{ign switch---}T^{--- Diode >I---- alternator}

                    ^I

           ^{Relay terminal 86}

 

 

^{Any diode that can handle 12v 5A of forward current should do.}

 

Reckon something like an optocoupler could be better though, you may even get something that's a complete package with a relay - or isolate the alternator from the ignition circuit via a relay too....

[JonnyAlpha]

The diode would go between where the the feed to operate the solenoid is tapped off and the alternator.

 

 

^{ign switch---}T^{--- Diode >I---- alternator}

                    ^I

           ^{Relay terminal 86}

 

 

^{Any diode that can handle 12v 5A of forward current should do.}

 

Reckon something like an optocoupler could be better though, you may even get something that's a complete package with a relay - or isolate the alternator from the ignition circuit via a relay too....

 

Ethel,

 

I have amended the wiring diagram to include a relay for the ECU. The ignition switched supply for the ECU / Coil Pack and Fuel Pump will connect to the Mini Fuse Box Terminal 2?

 

The relay for the FP will be in the boot with the 12v for terminal 30 coming from the +ve terminal on the battery in the boot.

The relay for the ECU will be in the dash with the 12v for terminal 30 coming from the Battery terminal on the wing mounted solenoid.

 

Where do I need to fit the protecting diode?

 

[Icey]

It’s not a protecting diode, as said before - that’s a different problem.

The diode goes inline with the alternator exciter wire, otherwise known as the battery or charge light on the dashboard

It’s needed because the alternator, when the engine is running, will feed current back through the ignition circuit (via the exciter wire) causing your ignition switched relay to stay energised. In turn this will hold your ignition system powered on, rendering your ignition switch ineffective (you won’t be able to turn the engine off).

The diode is used to ensure current can only flow into the alternator windings from the exciter wire, not out of it.

Pick a 12v diode with a high enough current rating (5a should do it, I think I used higher), then install it with the bias allowing current flow to the alternator. You can buy automotive diodes (i.e with spade connectors) from places like Polevolt.

[JonnyAlpha]

It’s not a protecting diode, as said before - that’s a different problem.

The diode goes inline with the alternator exciter wire, otherwise known as the battery or charge light on the dashboard

It’s needed because the alternator, when the engine is running, will feed current back through the ignition circuit (via the exciter wire) causing your ignition switched relay to stay energised. In turn this will hold your ignition system powered on, rendering your ignition switch ineffective (you won’t be able to turn the engine off).

The diode is used to ensure current can only flow into the alternator windings from the exciter wire, not out of it.

Pick a 12v diode with a high enough current rating (5a should do it, I think I used higher), then install it with the bias allowing current flow to the alternator. You can buy automotive diodes (i.e with spade connectors) from places like Polevolt.

 

Iv'e always struggled to find the exact wiring diagram for my 1982 HLE 1000 Saloon, but the one labelled:

ROVER MINI WIRING DIAGRAM MINI 1000 SALOON - MINI SPECIAL 1976 ON - PAGE 86-5

Seems to be as near as I can find.

 

So, according to this diagram, the diode would be fitted inline on the NY (Brown / Yellow) wire that runs from the Alternator to the No Charge Warning Lamp?

 

Alternator ----------Diode |<-----------Warning Lamp

 

No matter where I take my 12v feed or ignition Switched Supply for the ECU or Fuel Pump Relays?

 

Sorry I am not a vehicle electrician or a mechanic

[Icey]

It doesn’t really matter the year, brown/yellow was used until the MPi loom.

Easiest way to ensure it’s in the correct location is to either fit it under the bonnet on the wire going to the alternator or on either side of the dash warning lamp. You need to stop the current getting into the rest of the ignition switched circuit.

[Ethel]

I got curious how more modern cars got round the issue. Still not much wiser as many just show connection to an engine management black box, but the MGF diagram I found showed a diode on the ignition light, opposite side to the alternator. As Icey suggested.

 

It wouldn't be on your latest diagram. But as long as your "ignition switched supply" was on the opposite side of the diode to the alternator that's fine, just tap existing white wire(s) wherever is convenient. The left side of the fusebox, for example.

[Icey]

I got curious how more modern cars got round the issue. Still not much wiser as many just show connection to an engine management black box, but the MGF diagram I found showed a diode on the ignition light opposite side to the alternator. As Icey suggested.

I wouldn't be on your latest diagram. But as long as your "ignition switched supply" was on the opposite side of the diode to the alternator that's fine, just tap existing white wire(s) wherever is convenient. The left side of the fusebox, for example.

I suspect modern electronics also cut the exciter wire when the ignition is switched off. I’ll check one of my manuals for other cars, see if they show anything…

Edit:
Only other manual I have is for early MINIS (R50/53) - they just have a two-wire alternator.
But! The MPi Mini does actually still use brown/yellow for the dash warning lamp….guess what it has fitted…

Edited by Icey, 09 April 2023 - 09:52 PM.

[JonnyAlpha]

It doesn’t really matter the year, brown/yellow was used until the MPi loom.

Easiest way to ensure it’s in the correct location is to either fit it under the bonnet on the wire going to the alternator or on either side of the dash warning lamp. You need to stop the current getting into the rest of the ignition switched circuit.

 

So just to be clear cut and fit a diode inline on the Brown / Yellow wire between the Alternator and the No Charge Warning Lamp with the + (Anode) side of the diode on the Warning Lamp  side.

 

Alternator ---------(-ve)- Diode -|<-(+ve)----------Warning Lamp

 

 

I got curious how more modern cars got round the issue. Still not much wiser as many just show connection to an engine management black box, but the MGF diagram I found showed a diode on the ignition light, opposite side to the alternator. As Icey suggested.

 

It wouldn't be on your latest diagram. But as long as your "ignition switched supply" was on the opposite side of the diode to the alternator that's fine, just tap existing white wire(s) wherever is convenient. The left side of the fusebox, for example.

 

So pick up the switched ignition supply for my ECU Relay / Fuel Pump Relay and Smart Coil Pack (all shown with a yellow wire on the diagram I added earlier) on the left hand side of Fuse Terminal 1 (Which is a White Wire) and operates off of the ignition switch position II.

[Ethel]

Yes.

 

It's a handy place because there are 2 spades fixed together, but you could tap anywhere coming from the ignition switch if it's more convenient.

[JonnyAlpha]

I have updated the wiring diagram, to take into account the information gleaned in this thread and elsewhere. I have added a note ref the diode on the alternator / warning lamp wire, changed the Ignition Switched Supply to all come off of Terminal 1 on a Classic Mini Four Fuse Box.

I have also input the fuse ratings for the inline fuses on the ignition switched supplies.

 

Question:

There was a fuse annotated on the negative side of the Fuel Pump 12v Feed from terminal 87 of the relay, so I have added one on terminal 87 for the ECU. Is this correct?

 

[nicklouse]

Why earth to the engine? Earth to the same structure that the battery is earthed to.

 

as to the rest of the wiring. Not having the instructions to hand it is hard to say but stuff looks wrong to me. With power going the wrong way. But like I said nothing to check against.

[nicklouse]

You have your coil pack totally wired backwards.

it has no 12v feed. 
 

sorry you do but your diagram is very confusing as you have not marked your switched live as a positive.

Edited by nicklouse, 10 April 2023 - 07:08 PM.

[Icey]

You have your coil pack totally wired backwards.
it has no 12v feed.

Apart from the line that says 12v switched supply? It’s not a diagram I’d draw but it’s not that bad!

[nicklouse]

 

You have your coil pack totally wired backwards.
it has no 12v feed.

Apart from the line that says 12v switched supply? It’s not a diagram I’d draw but it’s not that bad!

 

See the edit done some time back.

[nicklouse]

Not happy about the fuel pump wiring.

 

are you sure that is not the feed for the relay from the ECU. How else does it prime the pump?