alternator charging woes...

[tedtaylor]

Summary:
Can't get the system charging correctly, ignition light not lighting

Equipment:
new battery
73 Elan Sprint (alternator conversion = no control box)
Lucas ACR17 (see picture) rebuilt with kit (regulator, brushes, rectifier, stator cap)
bypassed burglar alarm switch
2nd owner car last 5 years

Background history:
I remember very early on the red ignition light had worked at first, but shortly thereafter, never lit again.
Able to start car, but had to rev engine to get the system to charge. Been driving like that for last 4 years now, no apparent problems, long distances too, without issue or breakdown.
More recently, while starting car after longer periods of not driving, the typical hard-to-start routine of cranking over a lot to get fuel up and engine to fire. Winter set in (cold) and battery age, would not turn over enough to overcome that hard-to-start routine, so i bought the new battery.
Cranking over long enough now to start car, BUT....

i found again, it would charge only after revving, but additionally i noted that lights would dim at idle. So i suspected regulator in the alternator. I pulled alternator for rebuild. I noted brushes were not even worn down that much at all, but i replaced everything in the kit as instructed (rectifier, stator cap, regulator, brushes). I was very careful in soldering the wires using heat sinks.
Reinstalled rebuilt alternator and now, doesn't seem to be charging even after revving engine.....nothing, just running on battery feed.
I finally pulled the ignition light out of the tach and found the bulb burnt out. i replaced bulb and cannot get it to light with ignition on.

Diagnosis:
i have power going to the white wires on the ignition light housing in tach.
I do not have the control box any more since car was converted from generator to alternator, so wiring diagram differs from setup.
My alternator has an off-set 3 space connector with 4 wires going to it. I did not change the wiring on the connector. There is also a large heavy gauge wire connector (brown/yellow) going to the (+) connector on rear of alternator (see picture). The (-) connector stud on back of alternator is not connected to any other wires and left open. **NOTE UPDATE FURTHER DOWN THREAD*** as both studs are connected internally as one (picture included)
I checked ignition key switch and all connectors clean and connected.

Does this sound correct? What is wrong and why can't i get system to charge? Can't get ignition light to come on either. PLEASE HELP

[Billmack]

That looks like an old lucas 5 wire. Pretty sure you need the ground wire. Also its important for the indicator bulb to be good. System usually will not charge at all without it and may in fact have toasted another regulator already. Its another regulator problem that burns the charge indicator bulb. The ground is usually just a short black wire not in the harness with spade(lucar) connector on one end and loop on other often attached to rear mount bolt.

[Billmack]

The missing ground may be causing the light not to light since one of the skinny wires at the back of the alt supplies the ground to indicator light

[tedtaylor]

UPDATE:
old rectifier has separate studs

New rectifier has both studs connected internally (no separate ground)

instructions were vague to say the least. Says "detailed fitting instructions are enclosed"......NOT!!!!

[tedtaylor]

Update:
SUCCESS!!!
After researching online watching YouTube videos and checking Lucas ACR17 wiring diagrams (and there are several variations) i determined that i needed to make a jumper wire from the regulator case mounting screw to the nearest brush clamp hold down screw (see picture = red crimps/green wire). There should be a grounding strap, but my original older regulator did not have one, nor did the replacement parts in the kit, so i made my own.
Then i had to ground the black wire from regulator to the brush body hold down screw into alternator housing body.
That did the trick! I had it connected to the nearest brush clamp hold down screw.
The colors of the regulator wires are different between old (yellow & green) and new (black & yellow). I assumed the black was the old green (ground), but was wrong. The missing, now fabricated grounding strap, was replacing the old green wire.
ignition light now comes on with key ignition switch on and goes off once engine is started.

at idle, with lots of electric devices on (headlights, high beams, heater fan, etc.), the turn signals are slow/stalled and the air horns don't sound off (struggling), but as soon as i rev up the motor, everything bright and functional.
i used a volt meter and found 12.9 volts at idle, but up to 14 volts revved up.
is this normal? or should it be "regulated" more evenly??

[RichardS]

Hi Ted
Have you checked your battery earth?
In the past I have usually found slow indicators etc due to a poor earth somewhere. There are several past threads on checking and improving earthing if this is the case
Richard

[Andy8421]

The regulator in a 17ACR has a target output voltage around 14V (it is a bit temperature sensitive). The current output of the alternator is however dependent on revs - the higher the revs, the more current it can deliver.

With no load, the alternator voltage should remain constant (ish) at 14V across the rev range. If you ask more current from the alternator than it can deliver at a certain revs, then the voltage will dip down. This is the effect you are seeing, at low revs the alternator can't deliver enough current to keep the voltage at 14V, and the voltage dips. As the revs pick up the alternator can deliver more current and achieve the target voltage.

This is entirely normal, and nothing to worry about.

I have never worked out the ratio of pulley size on the Elan, but the max recommended speed of a 17ACR from Lucas' spec sheet is 12,500 rpm. Lets assume a red line of 6,500 rpm on the engine, and that Lotus aimed for the alternator max speed at engine red line. That gives a pulley ratio of 2:1 (ish). At a 800 rpm tickover, the alternator would only be doing 1600 rpm, which is way down the amperage curve. Lotus probably designed a bit of headroom into the ratio, so the alternator speed could be even lower at tickover. At 1600 rpm alternator speed, you will only get 15 amps from a 17ACR, not the rated 36 amps. See below.

https://www.coolcatcorp.com/Lucas/Lucas15-18ACRalternatoroutputcurves.gif

edit: Should have added, its the combination of low revs and lots of load that is causing the voltage dip. If you switch off the loads, even at tickover output voltage should go back up to around 14V - although if the battery isn't fully charged it may take some time to float the battery up to this level.

[webbslinger]

My engines low rpm charging was terrible before I discovered it had a smaller than stock crank pully - so that may be worth checking - but even with the stock pully it is still only poor at idle. The idle charging would benifit from a slightly larger crank pully, but that would spin the alternator pretty fast at full rpms.

[gjz30075]

Ted, how's the belt tension?

[tedtaylor]

Ted, how's the belt tension?

actually very loose....well let's just say not real tight? i'm trying to save my water pump!

THanks everyone for chiming in. My stubborn persistence kept me on the path.... it was 1:30 in the morning when i thought about the wiring corrections, and went out in the cold garage to fix it right. Now i can get some sleep...

[Billmack]

I thought something like that!

[billwill]

Np-one has mentioned the following point and the fact that yours is now working means that you do have an appropriate bulb.this is for the benefit of later viewers of this topic.

The IGNITION CHARGING LIGHT MUST BE AN INCANDESCENT BULB NOT AN LED.
and it has to be a particular wattage, though I forgot the exact figure.

This is because the current flows both ways through the bulb, initially it provides the biasing current from the battery for the field coils to start the alternator working.

[tedtaylor]

Actually took a real good test drive today. charging fine.
light on with key on, goes off when started. used all my electric devices and signals flashing good, fan strong, wipers.....uh, slow, but normal.
i'm very satisfied with my rebuild alternator project.
the wiring was a bit tricky and different (old vs. new), but all came together fine and dandy.
it was brisk winter drive, but enjoyable.
thanks again everyone.

[0005K]

I have a related issue with my RDent aftermarket alternator on my Federal S4. Alternator has zero miles on it, and I don't think I could have done anything to burn it out. The ignition light won't light. With the ignition on I get 12V all the way down to the brown/yellow wire. When I ground the brown/yellow wire at that point, the ignition lamp lights up, but not when normally connected to the alternator. I tried grounding the alternator case with an alligator clip jumper, but that didn't work. Do I need to add a ground somewhere?
I have new British Wiring / Autosparks harnesses. The alternator is connected to the engine. The engine has a braided wire ground at an engine mount. I do not have an external relay box. The alternator connections go into the harness. The big brown charging wire goes to the solenoid and is on top of the + wire from the battery. I have continuity to the ignition lamp with the brown/yellow wire.
Any thoughts? I'm at the point of pulling the alternator and taking it to my local auto supply to see if it is OK.
Cheers
Dick

[gjz30075]

Same issue here with the Nippondenso from RD. Worked fine for a while then quit charging. I had it
rebuilt locally and I experienced the same issues as you. My guess is there is a newer internal
regulator that requires a different wattage bulb and you could have a newer Nippondenso with the
*alleged* newer regulator. I eventually changed to a Hitachi alternator and all is well.