Hey there,

Here again as i have been chasing what i think must be a charging / alternator or possibly engine harness wiring harness issue. I realise thats 3 categories each extensive on their own.

So what i am faced with is a rev drop (sounds like 100 to 150 revs) when the headlights come on and sometimes the ''IGN'' light will remain illuminated when starting the car up, if i don't rev it a bit. Like two small throttle applications. The alternator is not the original 65amp unit, its a 55amp one. The proper one along with an NOS engine loom are underway for good measure and also because i am an NOS parts hoarder.

The coil is new and good quality too. The ballast resistor on these was integrated in the wiring harness. Is that worth checking too ? Alternator reads 14.0 volts at idle and that drops to 13.8 volts when still at idle but with the headlights switched on. Revs drop when you switch on the headlights as said and pick up again when you switch them off. The voltage gauge in the car (the original one - Smiths isn't it?) reads on the higher end of the normal scale but does fluctuate slightly when the above happens (which is what it should do i think given there is voltage drop). Also the earthing points have been cleaned and the earthing strap replaced.

I suspect an alternator regulator might be my source of issues. Not sure however. Are the 14.0 reading and the 0.2 drop an indication of charging issues ? The rev drop surely means the engine works harder in correlation to the alternator working harder. Can it be that the alternator is by default a smaller one ? (55amps instead of the factory 65amps).

Lastly the alternator part of the harness is kinda strange. Normally there are two brown wires and one brown / yellow. In my case the thicker brown wire is connected as well as the brown / yellow one (in their respective positions) but the thinner brown wire has been disconnected and secured on the harness with a zip tie (see the photo).

Please let me know of any advice on how to approach this apart from going in and replacing the whole bunch (engine loom and alternator).

Many thanks !!!

Jim_P said:

Hey there,

Here again as i have been chasing what i think must be a charging / alternator or possibly engine harness wiring harness issue. I realise thats 3 categories each extensive on their own.

So what i am faced with is a rev drop (sounds like 100 to 150 revs) when the headlights come on and sometimes the ''IGN'' light will remain illuminated when starting the car up, if i don't rev it a bit. Like two small throttle applications. The alternator is not the original 65amp unit, its a 55amp one. The proper one along with an NOS engine loom are underway for good measure and also because i am an NOS parts hoarder.

The coil is new and good quality too. The ballast resistor on these was integrated in the wiring harness. Is that worth checking too ? Alternator reads 14.0 volts at idle and that drops to 13.8 volts when still at idle but with the headlights switched on. Revs drop when you switch on the headlights as said and pick up again when you switch them off. The voltage gauge in the car (the original one - Smiths isn't it?) reads on the higher end of the normal scale but does fluctuate slightly when the above happens (which is what it should do i think given there is voltage drop). Also the earthing points have been cleaned and the earthing strap replaced.

I suspect an alternator regulator might be my source of issues. Not sure however. Are the 14.0 reading and the 0.2 drop an indication of charging issues ? The rev drop surely means the engine works harder in correlation to the alternator working harder. Can it be that the alternator is by default a smaller one ? (55amps instead of the factory 65amps).

Lastly the alternator part of the harness is kinda strange. Normally there are two brown wires and one brown / yellow. In my case the thicker brown wire is connected as well as the brown / yellow one (in their respective positions) but the thinner brown wire has been disconnected and secured on the harness with a zip tie (see the photo).

Please let me know of any advice on how to approach this apart from going in and replacing the whole bunch (engine loom and alternator).

Many thanks !!!View attachment 312845

Click to expand...

The thin wire being disconnected might account for the ignition light but if it's the connection I think it is, the light should not come on at all. 14 volts is OK but a bit on the low side for a modern Lead/Calcium battery. If the revs drop when the alternator is under load, that is down to the engine not the alternator. Needs a wiring diagram to be sure of what should go where, but the alternator, although being a low amperage unit, is certainly working.

Datatek said:

The thin wire being disconnected might account for the ignition light but if it's the connection I think it is, the light should not come on at all. 14 volts is OK but a bit on the low side for a modern Lead/Calcium battery. If the revs drop when the alternator is under load, that is down to the engine not the alternator. Needs a wiring diagram to be sure of what should go where, but the alternator, although being a low amperage unit, is certainly working.

Click to expand...

Hey there,

Thanks for the response!

Got the diagram. The brown wires go to the starter. The brown / yellow to the light. The brown ones don't have a relation with the ign light.

It should come on when the key is on the second position and go out when you fire the Rangie up.

When you say engine issue what sort of thing should I look into? I mean it surely must be electrics related. I do think that the engine loom is my issue to be honest. It was an ex Fire Truck and had some mods on it.

Jim_P said:

Hey there,

Thanks for the response!

Got the diagram. The brown wires go to the starter. The brown / yellow to the light. The brown ones don't have a relation with the ign light.

It should come on when the key is on the second position and go out when you fire the Rangie up.

When you say engine issue what sort of thing should I look into? I mean it surely must be electrics related. I do think that the engine loom is my issue to be honest. It was an ex Fire Truck and had some mods on it.

Click to expand...

Put load on the engine and if it's not making enough power to cope with the load, the revs will drop. For example, on one of my cars with electronic injection, switching on any load causes the ECU to increase idle revs.
As you say, the ignition light should come on with the key in the second position and go out when the alternator starts to charge, in some cases, an increase in revs is needed to kick the alternator to start charging.

Datatek said:

Put load on the engine and if it's not making enough power to cope with the load, the revs will drop. For example, on one of my cars with electronic injection, switching on any load causes the ECU to increase idle revs.
As you say, the ignition light should come on with the key in the second position and go out when the alternator starts to charge, in some cases, an increase in revs is needed to kick the alternator to start charging.

Click to expand...

I see. That's how I had it cleared in my head too. Just wondered whether you meant something different.

Couldn't it also be a case of a weak alternator causing the rev drop? As it's not compensating for the load thus robbing power from anywhere else? The engine I have opened up to do the heads. Cam was excellent and its not tappet at all. The carbs have been rebuilt properly and it pulls very nice.

Thats why I was focusing more on the alternator and wiring topic.

Thanks for always being one of the first to come by and respond to the threads I post man. Appreciate it!

Revs dropping as the load on the alternator increases is entirely normal.
If the revs drop too far then the ignition light may well illuminate or flicker.
If you increase the revs it should go out.

The later Classic Range Rover was fitted with a stepper motor & a more sophisticated ECU which would automatically increase the idle revs as loads increased.
The stepper motor is a motorised valve on the rear of the plenum chamber which opens & closes - effectively an automatic throttle increase.
Once the load is off the ECU will then decrease the revs to stay within the normal idle range for that engine.
This applies to any extra load on the engine, such as turning power steering when stationary or at very low speed (such as manoeuvering a trailer/caravan) or putting the car in gear with an automatic gearbox.
Yours on carbs does not have this & neither do many of the earlier 3.5EFis - including mine which is an '86 3.5EFi with the 4CU ECU.

Over the years on a number of cars I've had alternators fail, usually the charge light stays on or sometimes remains on very faintly which is often only visible at night.
I had the voltage regulator fail on one on the RRC. Blew several fuses on aftermarket fitments incl the radio & thoroughly cooked the battery. Voltage being put out was in excess of 19 volts & I consider myself lucky it didn't damage any of the wiring.

Jim_P said:

I see. That's how I had it cleared in my head too. Just wondered whether you meant something different.

Couldn't it also be a case of a weak alternator causing the rev drop? As it's not compensating for the load thus robbing power from anywhere else? The engine I have opened up to do the heads. Cam was excellent and its not tappet at all. The carbs have been rebuilt properly and it pulls very nice.

Thats why I was focusing more on the alternator and wiring topic.

Thanks for always being one of the first to come by and respond to the threads I post man. Appreciate it!

Click to expand...

An alternator under load takes a fair bit of power but with a hulking great V8 driving it, I wouldn't expect much of a drop in revs really. I have no idea if the drop in revs you are experiencing is normal for that engine, needs someone who knows the Classic to comment really.

Ratae said:

Revs dropping as the load on the alternator increases is entirely normal.
If the revs drop too far then the ignition light may well illuminate or flicker.
If you increase the revs it should go out.

The later Classic Range Rover was fitted with a stepper motor & a more sophisticated ECU which would automatically increase the idle revs as loads increased.
The stepper motor is a motorised valve on the rear of the plenum chamber which opens & closes - effectively an automatic throttle increase.
Once the load is off the ECU will then decrease the revs to stay within the normal idle range for that engine.
This applies to any extra load on the engine, such as turning power steering when stationary or at very low speed (such as manoeuvering a trailer/caravan) or putting the car in gear with an automatic gearbox.
Yours on carbs does not have this & neither do many of the earlier 3.5EFis - including mine which is an '86 3.5EFi with the 4CU ECU.

Over the years on a number of cars I've had alternators fail, usually the charge light stays on or sometimes remains on very faintly which is often only visible at night.
I had the voltage regulator fail on one on the RRC. Blew several fuses on aftermarket fitments incl the radio & thoroughly cooked the battery. Voltage being put out was in excess of 19 volts & I consider myself lucky it didn't damage any of the wiring.

Click to expand...

Hey there,

Thanks for the great info! Got ya.

Yep indeed the later ECU systems do have the rev increase facility.

What I am gonna do since I will have them at my disposal, I am gonna put the new alternator and the harness on the Rangie. Seems like good practice since the wiring especially has had some modifications done to it.

Gonna report back once its all done. I think it will be okay fingers crossed.

Thanks again!

Datatek said:

An alternator under load takes a fair bit of power but with a hulking great V8 driving it, I wouldn't expect much of a drop in revs really. I have no idea if the drop in revs you are experiencing is normal for that engine, needs someone who knows the Classic to comment really.

Click to expand...

Indeed it does. The V8 statement is indeed true. I think the rev drop I am seeing or shall I say listening is enough to cause discomfort if you know what I mean.

Gonna replace the loom and alternator and report back.

Cheers!

Jim_P said:

It was an ex Fire Truck and had some mods on it.

Click to expand...

TACR2 by any chance ?

norseman said:

TACR2 by any chance ?

Click to expand...

Nope hehe. First year of the official Rover 4 door Range Rovers i think. Its an 82. It was registered in Germany. The German Fire Departments seemed to really like the Rangies. They began using them in 74 i think.

Not a TACR2 though lol.

Sooo,

Figured what the extra wire that had been left disconnected is. Its the battery sensing one. The early A133 Lucas alternators were battery sensed ones. The newer ones from what i can understand are machine sensed. The brown thin one would normally connect to an ''S'' marked connection on the back of the alternator. Confirmed this through the wiring diagram.

The only alteration I can spot on the harness are the spade terminals in place of the the original ring terminals.

Gonna replace the alternator for a start then move on to the harness after more checking with the new alternator.

Cheers guys !

Jim_P said:

Sooo,

Figured what the extra wire that had been left disconnected is. Its the battery sensing one. The early A133 Lucas alternators were battery sensed ones. The newer ones from what i can understand are machine sensed. The brown thin one would normally connect to an ''S'' marked connection on the back of the alternator. Confirmed this through the wiring diagram.

The only alteration I can spot on the harness are the spade terminals in place of the the original ring terminals.

Gonna replace the alternator for a start then move on to the harness after more checking with the new alternator.

Cheers guys !

Click to expand...

That is old, not seen remote voltage sensing for a very long time. All alternator regulators sense at the alternator now.

Datatek said:

That is old, not seen remote voltage sensing for a very long time. All alternator regulators sense at the alternator now.

Click to expand...

I know its bloody old. That's why they left it (the thin brown wire) disconnected when the then new unit replaced the original Lucas one.

Ratae said:

Revs dropping as the load on the alternator increases is entirely normal.
If the revs drop too far then the ignition light may well illuminate or flicker.
If you increase the revs it should go out.

The later Classic Range Rover was fitted with a stepper motor & a more sophisticated ECU which would automatically increase the idle revs as loads increased.
The stepper motor is a motorised valve on the rear of the plenum chamber which opens & closes - effectively an automatic throttle increase.
Once the load is off the ECU will then decrease the revs to stay within the normal idle range for that engine.
This applies to any extra load on the engine, such as turning power steering when stationary or at very low speed (such as manoeuvering a trailer/caravan) or putting the car in gear with an automatic gearbox.
Yours on carbs does not have this & neither do many of the earlier 3.5EFis - including mine which is an '86 3.5EFi with the 4CU ECU.

Over the years on a number of cars I've had alternators fail, usually the charge light stays on or sometimes remains on very faintly which is often only visible at night.
I had the voltage regulator fail on one on the RRC. Blew several fuses on aftermarket fitments incl the radio & thoroughly cooked the battery. Voltage being put out was in excess of 19 volts & I consider myself lucky it didn't damage any of the wiring.

Click to expand...

Hey there mate !

Good morning ! I wanted to ask you since you have been faced with a faulty regulator that won't regulate voltage and allow excessive voltage to pass through. Would it be possible in such an instance that the wiring would melt ? Any possible part of it i mean.

Just gathering info and opinions on the topic.

Jim_P said:

Hey there mate !

Good morning ! I wanted to ask you since you have been faced with a faulty regulator that won't regulate voltage and allow excessive voltage to pass through. Would it be possible in such an instance that the wiring would melt ? Any possible part of it i mean.

Just gathering info and opinions on the topic.

Click to expand...

As I said on your other thread on the subject, the alternator regulator is not responsible for your melted wire. High voltage from a duff regulator may blow bulbs, it may even cause the battery to explode but it would not account for one melted wire to a rear light.

Datatek said:

As I said on your other thread on the subject, the alternator regulator is not responsible for your melted wire. High voltage from a duff regulator may blow bulbs, it may even cause the battery to explode but it would not account for one melted wire to a rear light.

Click to expand...

I know you said that mate, I am only collecting info and possible scenarios from different people. Its not a matter of not showing trust in your words. I appreciate that you always show up first when i post a new thread.

As said i am only trying to gather info. Thanks again and keep well !

Jim_P said:

Hey there mate !

Good morning ! I wanted to ask you since you have been faced with a faulty regulator that won't regulate voltage and allow excessive voltage to pass through. Would it be possible in such an instance that the wiring would melt ? Any possible part of it i mean.

Just gathering info and opinions on the topic.

Click to expand...

Blew the fuses for the aftermarket immobiliser & the aftermarket radio/cd player.
I've since replaced both items - nothing to do with this issue - & can't remember what fuses they had in.
Thoroughly cooked the battery, it swelled up a bit too - had to replace it.
Nothing else damaged & none of the bigger fuses blew, which would suggest that the load on the wires wasn't enough to melt or set light to stuff.
Only time I've melted wires is direct short from a battery fed live to ground.

Just remembered. It blew the fuse on the petrol/LPG changeover - manually switched - as well & that's a 7.5 amp blade fuse.
Default position of the relay is petrol & I can't remember which fuel I was on at the probable time it went so it wouldn't have stopped the car.
If I had been on LPG the loss of power to the relay would have seen it make the contact required to activate the injectors so I may not even have noticed.