Temerpature gauge goes straight to max

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You seem to be missing the point that the splice to the lift pump relay is before the connection to the alternator. If on ignition 12 volts is going to the D+ terminal from pin 15 on the BECM to excite the field coils 12 volts is also going to the lift pump relay. If you have a supply then split it to two bulbs and ground both they will both light.
Sorry, you are missing the point, the splice is after the resistor in the BECM, so the D+ is at ground zero until the aternator starts charging, meaning both sides of the relay are also at ground zero so how will it operate?
Two bulbs of different resistance values will not necessarily both light.
 
Sorry, you are missing the point, the splice is after the resistor in the BECM, so the D+ is at ground zero until the aternator starts charging, meaning both sides of the relay are also at ground zero so how will it operate?
Two bulbs of different resistance values will not necessarily both light.

When the ignition is switched on the relay is pulled by the tap to number six glow plug until the glow lamps go out. So the relay does have a circuit. If there is 12 volts from pin 15 to the relay and to D+ the relay MUST be pulled. Therefore there CANNOT be 12 volts from pin 15 to the relay and D+. The exciting voltage if there is any must be far less that 12 volt or the relay would be pulled. Simple as that.
 
When the ignition is switched on the relay is pulled by the tap to number six glow plug until the glow lamps go out. So the relay does have a circuit. If there is 12 volts from pin 15 to the relay and to D+ the relay MUST be pulled. Therefore there CANNOT be 12 volts from pin 15 to the relay and D+. The exciting voltage if there is any must be far less that 12 volt or the relay would be pulled. Simple as that.
To quote you, you can take a horse to water etc.:rolleyes:
If there was no 12 volts providing an excitation current the alternator may never start to charge.
Do you not understand that 12 volts via a resistor or bulb to a fecking low resistance coil in the alternator result in the potential at the D+ being at zero? This is what produces the excitation current flow.
 
To quote you, you can take a horse to water etc.:rolleyes:
If there was no 12 volts providing an excitation current the alternator may never start to charge.
Do you not understand that 12 volts via a resistor or bulb to a fecking low resistance coil in the alternator result in the potential at the D+ being at zero? This is what produces the excitation current flow.

But it's not going to a low resistance coil when it is tapped off to the relay is it. I am not interested in the potential at D+ just the voltage at one side of the relay pull circuit.
 
But it's not going to a low resistance coil when it is tapped off to the relay is it. I am not interested in the potential at D+ just the voltage at one side of the relay pull circuit.
If the apparent voltage at D+ is zero, then how can it be different at the relay? The two are effectively directly connected together.
 
If the apparent voltage at D+ is zero, then how can it be different at the relay? The two are effectively directly connected together.

So basically what you are saying is with ignition on we have 12 volts at pin 15 to excite the field coils. This 12 volts travels up the wire to the splice, to the relay and to D+ but because the wire is connected to D+ it disappears up it's own orifice. That is bit i am struggling with.
 
So basically what you are saying is with ignition on we have 12 volts at pin 15 to excite the field coils. This 12 volts travels up the wire to the splice, to the relay and to D+ but because the wire is connected to D+ it disappears up it's own orifice. That is bit i am struggling with.
That's one way of putting it:)
The armature of the alternator has a very low resistance so is much the same as a direct connection to ground.
 
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