Electric trickery - the prince of darkness strikes again!

[Mike Stevens]

the line I'm following is that the battery is the main source of power rather than the alternator, Certainly battery voltage droops with load, droop being dependent on the load itself, hence the ballast ignition system as the voltage drops by a few volts on cranking (albeit drawing 100, or more amps.). At idle the alternator should be generating above nominal battery voltage and the increased load should not really impact the alternator as the battery should feed the load?

Sorry Alec, can't agree there! James measured 14.1V engine running, lights OFF and 12V with the fan on. 14.5 V can only come from the alternator (too high from a battery) so it was charging at the time. With the fan on, dropped down to 12V, so part of this load will be from the alternator - remember it is a high output one, so could be producing more output at tickover than standard. It is still odd though.

Things to try/think about.

1. What size pulley is on the alternator. If too small, it will run the alternator faster.
2. This fan - I assume it's rad cooling fan? Where is it wired in the system? The best way would be a direct connection from the battery (fused) via a relay to the fan. The current then comes directly from the battery rather than through the loom - it might be quite a current. Also see below about extra wire!
3. Luminition. This is the ignition thingy? How is it wired to the coil with the ballast resistor?
4. It might be interesting to short out the ballast resistor and see if that has an effect on the stalling. If not, it's not a coil thing.
5. Unplug the alternator and see what happens with the lights on. Again, perhaps giving some clues.
6. More when I can think of it!

As you have so many non-standard parts (all of which are a good idea and nothing wrong with them) it makes it a bit harder to think of issues.

BTW, when measuring voltages, try to measure across the battery. The loom wiring is not up to modern standards and there will be odd volt drops all over the place. In fact, I would be tempted to fit a wire DIRECT from the alternator output to the battery +ve. How many THICK brown wires are there in the connector on the alternator? Hopefuly 2, but if not, I would fit this extra wire, especially with the high output alternator.

I'll keep thinking....

Cheers,
Mike.

[squeezer]

Hi,

The earth strap 'appears' to be OK though I may replace this anyway. The voltage at idle with the lights on was showing just over 14v. I have cleaned the strap earth connection, the earth connection by the front lights and also the earth for the kenlowe. I have also increased the idle speed slightly so we'll see how I get on. The wife's 306 slows when the fan cuts in so perhaps it is the increased load on the alternator (assuming the earths/wiring are all ok). And yes - it does have a lightened flywheel but not sure by how much (I wouldnt like to drop it on my big toe though ).

Will let you know how I get on...

Thanks for all the replies so far!

[Alec]

Hello Mike,

"James measured 14.1V engine running, lights OFF and 12V with the fan on. 14.5 V can only come from the alternator (too high from a battery) so it was charging at the time. With the fan on, dropped down to 12V, so part of this load will be from the alternator"

The thing is you can't separate them, they are one system,
battery voltage will equal alternator voltage and should only start droop when the alternator reaches full output current. I'm saying the battery somehow is not powering the fan and or the lights but the alternator is?
I have a Kenlowe fan but don't remember what it's rating is although 10 amps comes to mind? I'll try and measure it tomorrow. But that is not a huge load, and James mentions worrying about the load of lights, heater etc in winter. Well my fan rarely runs even in summer (no mechanical fan fitted) so I don't think it should be a problem.

Alec

[squeezer]

Hi.

With or without the alternator disconnected, regardless of the fan or lights being on, directly powering the coil made no difference to how the engine performed (I haven't tried this with the feed to the lumenition). The kenlowe thermostat is wired directly (via a fuse of course!) to the +ve terminal of the battery.

With the alternator disconnected (std pulley size), there was no difference when either the lights were on or the fan was running. This was at just over 12v showing on the gauge so it it smply the alternator loading which is causing this problem? One of the reasons I had lowered the idle speed was to reduce 'running on' but I have recently purchased an 'anti run-on valve' which should eliminate this.

I'm off to Fitchets tomorrow to get a new ig'n switch and earth strap. If this doesn't make any difference I may resort to getting a new main loom (ouch). Will update when new switch/earth are fitted.

Regards

James

[Alec]

hello james,

I can see no reason at all to replace the main loom, or even the ignition switch.

If you see 12 volts without the alternator connected but with lights and fan on then it proves the battery is good and your load not excessive. What I have been trying to say is that if the alternator is being loaded so that it stalls the engine, I don't understand why as the battery should be taking that load. What is your alternator size? Assuming 50 amps and 14 volts (idle voltage?) that is 700 watts, marginally less than one horsepower, should that stall an engine?

Alec

[Alec]

Hello all,

just a little follow on.

I measured the current of my Kenlowe fan at 5 amps, and at idle with full headlights and the fan on or off made no difference to my idle speed. This is at a very low tickover speed, about 500 rpm, and the system voltage was about 11.5 volts with both lights and fan.

Alec

[Mike Stevens]

With the alternator disconnected (std pulley size), there was no difference when either the lights were on or the fan was running. This was at just over 12v showing on the gauge so it it smply the alternator loading which is causing this problem? One of the reasons I had lowered the idle speed was to reduce 'running on' but I have recently purchased an 'anti run-on valve' which should eliminate this.
James

I agree with Alec - you don't need a new loom etc. Am I correct in thinking that if you disconnected the alternator, the problem disappears? I have to say, that this would suggest that it's the excessive alternator load that is causing the problem. 14.5V at tickover is higher than I would expect from a standard Lucas 15/16/17ACR type, so that also suggests the uprated one you have can produce higher output at tickover. At this voltage, the alternator will be putting current into the battery, but if the battery is in a good state of charge, it won't be much, so a big change on current happens when extra load comes on. The theory goes summat like this. Yes, the battery/alternator can be treated as one, but if the volts drop with load, (which they will) this means that the alternator (which was trying to produce 14.5V) will produce more current up to what it CAN do at that speed. A 15/16/17 ACR doesn't give that much at tickover speed, but if your uprated one does, then that load goes back to the engine. As the load goes up and the voltage comes down, the share of the current will change so that more will come from the battery. Blip the throttle and the alternator can now give a lot more power so the volts rise for a bit.

I believe that although the electrical power you are drawing is small compared to the engine max power out, at tickeover, it is doing hardly anything. Also with an uprated CAM (GT6 one was it?), tickover will be a bit lumpy as the inlet charge goes past the carbs a few times at tickover with the large timing overlap. Funnily enough, the 'short' inlet manifold should be better on this front. Again, the lightened flywheel will make the lumpy tickeover worse. (And I wouldn't like to drop on foot either!)

When it stalls, is it a 'cut' type of stall or just the tickover goes far too low? You said that you lowered the tickover to stop run-on. I found this was helped by running the mixture just on the rich side. How do you set up the carbs? I do it by ear, but leaving at that point made the run-on awful. Making it slightly richer helps, by having a bit more cooling from the extra fuel I suppose.

To be honest, I can't think of a solution. Modern cars get over this change in load at tickover (aircon cycling, bigger alternators etc) by using Idle Control Valves and a computer to control the engine revs. NOT what we are into with the Triumphs, (although it might be an interesting project!). The only thing I can think of is to raise the tickover slightly - assuming you can control the run-on. Have you tried a 'normal' Alternator? Or maybe a bigger pulley on the one you have? Just a thought.

Sorry if this post is a bit long. Just thinking while typing!

Cheers,
Mike.

[Alan Chatterton]

I am thinking that it might be something to do with the +ve feed to the lumintion module.

It sounds like when the voltage drops (when the fans kick in) that there is a loose connection somewhere (luminition?) that doesn't like a low voltage.

Where have you got the power feed to the electronic ignition from? I'm guessing from an ignitioned live off the fuse box?

Try connecting the +ve feed to the luminition module straight from the battery to test this theory.

I remember when i was fitting leccy ignition that the power supply to it had to be clean and over 12v, otherwise it wouldn't work...........