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Disconnect the generator from the regulator (probably easiest to simply take the wires off the generator).
Connect a jumper from DF on the generator to the generator frame. Now run the engine and measure the voltage from ground to D+ on the generator.As you increase the engine speed, the voltage should jump up to +35 volts or so (@3000 RPM).
If it passes this test, the generator is good.My LR dashboard configuration from Left to Right.
Gas gauge / speedometer / tach / amp gauge / interior Light / Oil pressure
between the speed and tach are some lights
Top light (red) high low beam
below (blue) Alternator exciter light
below that 2 (green) turn signal indicators
I’ll put a picture of the dash in my gallery if it is not already there.
Dick, it sounds like who ever built your car wired two of the idiot lights incorrectly.The blue light is normally used for hi-beams (not just in our TDr, it’s an industry standard).The red is used to indicate whether the charging circuit is charging or discharging.When you turn your inigition key on, the generator/altenator light should light.It will likely flicker when you turn the engine over. At least mine does. That occurs because the generator is turning with the engine. So it’s putting out a little electricity.Once you are at a steady idle, the idiot light should go out.All the idiot light is telling you is that the charging circuit is charging or discharging.If the light stays on once the engine is running, I see a few possibilities:- a fuse is blown
- some sort of wiring problem (always fun to diagnose!)
- voltage regulator is shot
- generator is shot
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica RoadsterIf you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)
My LR is also factory built and I think the guy who converted from a generator to an alternator added an extra light. Red light on mine is high/low beam and blue is alternator. Blue stays on until rpm’s increases or will shut off after a few minutes. Alternator will not charge battery until light goes off, amp gauge verifies that.
My TDr also came with a red Hi-beam and blue generator light. That made absolutely no sense to me since red is used as a danger color. I re-wired the lights to make blue the hi-beams and red for the generator
If your belt breaks, you’re basically going to have to buy a new engine after only a very few minutes of running.
This comment, and variations of it, confuse me. And I think it is incorrect:
“Alternator will not charge battery until light goes off, amp gauge verifies that.”I’m not expert, but that never stopped me from opining before!The light is an indication of what is happening. It is in the circuit, telling you if things are ok (it’s out) or not ok (it’s on). It is not a switch, controlling the electric flow.The ammeter (amp gauge) is measuring electric current (i.e.: the amperage) flowing to the battery or from the battery.I’m sure you see the light is going out when you see the ammeter register positive; current is flowing to the battery. But the light is not the cause. The light is an effect.And you see the light come on when current is not flowing to the battery, because of a blown fuse, loose wire, bad voltage regulator or a failing generator or alternator. When the light is on, you should also see a negative reading on your ammeter.But I truly believe it is not the light that is serving as a switch and either allowing (or not allowing) the alternator or generator to charge the battery.Am I really wrong about this?PMOSSBERG2015-03-06 09:55:04
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica RoadsterIf you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)
And for what it’s worth, those LR guys must have been mavericks. 👿
Or maybe the same knucklehead wired every dash and didn’t know blue from red! 😆Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica RoadsterIf you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)
My car had (originally) blue for high beam, red for oil pressure and green for gen. That is how it still is.
I switched my generator out for an alternator the first week I got my Duchess. I also replaced my blue warning light for a red one. The high beam indicator is mounted on the chrome headlight shell and it shines blue. My turn signals are green. My kit was factory built by Classic Roadsters LTD. Im wired from the alternator to the warning light then to the fuse panel.
When I installed the alternator I was able to get rid of the voltage regulator and the excess wires. Fewer places for electric gremlins to hide.PMOSSBERG wrote:And for what it’s worth, those LR guys must have been mavericks. 👿Or maybe the same knucklehead wired every dash and didn’t know blue from red! 😆There’s a reason the military won’t allow you to be an electrician if you’re colorblind, and red-green is the most common form… 😆
Early FF TDr on 69 VW pan
Slowly coming back from the ashes...Rick, you didn’t really “get rid” of a voltage regulator. Alternators typically have the voltage regulator built into the alternator housing.
Nobody commented on the “is the idiot light actibg as a switch or is it just a status light” issue. I feel so ignored.
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica RoadsterIf you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)
Paul, I’ve always heard that an alternator needed the resistance of the idiot light to excite it and begin charging. I’ve never heard that about generators, and I have seen lots of generators with only an ammeter. I don’t claim to know the final answer…
Early FF TDr on 69 VW pan
Slowly coming back from the ashes...I keep learning stuff every day!
Did some digging around. We’re not the only ones to talk about this. I found search results in at least a half dozen car related forums.The resistance provided by the idiot light does initiate the charging sequence for alternators, in “modern electrical systems.” This is the closest to a layman’s description that I’ve been able to find.The alternator light does work by a balance. When you turn on the key, 12 volts is supplied to the alternator’s field windings through the idiot light. This gives an indication that the alternator’s field circuit is intact, and it also provides the current to start the alternator charging. In fact, the alternator may fail to charge if that light bulb is burned out. When the engine starts and gets up to a high enough rpm for the alternator to start putting out voltage, there is a diode inside that takes some of the output voltage and featured back to the terminal that goes to the idiot light. The net result of this is that when the engine is running and up to proper rpm, the idiot light is receiving 12 volts at both ends, which means that the total voltage drop across the light is the zero volts and the light doesn’t light.One last thought on the idiot light issue, am I reading this article correctly to mean the external voltage regulator provides the switching functiona generator does not need the idiot light to commence charging?For VW’s specifically, this is my favorite comment from thread on the Samba (the underlining is mine). Roy alluded to this earlier in this thread.These are air-cooled cars, and don’t have low coolant level lights or coolant temperature gauges. They have a generator light to tell you if the generator isn’t working, (ie, not turning) and if it’s not turning, the fan isn’t turning, and your cooling system isn’t working.There are other reasons the idiot light could come on. But if it is because the generator is not turning…the expensive noises and smoke will commence within minutes, if not seconds.Back to the initial question about problems with the generator. MG wanna B said he followed procedures in a bunch of tech articles. I can’t say either of these are among his resources, but here are a couple good ones:Rob & Dave’s Aircooled instructions for diagnosing generator problems: http://www.vw-resource.com/generator.htmlHere’s another great write up: http://www.justanswer.com/classic-cars/4p00g-volkswagen-sandrail-1600-cc-vw-motor-sandrail.htmlAnd some info about replacing a generator with an alternator:Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica RoadsterIf you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)
One more “last” comment. 😉
Found this on the Samba: “…a generator with regulator does not need the initial pulse of 12 volts to start producing electricity as a alternator….” http://www.thesamba.com/vw/forum/viewtopic.php?t=463479So…with an alternator, the idiot provides the current to excite the alternator and begin chargingwith a generator, the idiot light is only a status bulbRight?Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica RoadsterIf you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)
And finally (for real this time), from Rob and Dave again: http://www.vw-resource.com/output.html Basically:
Alternators are activated by current (i.e.: flow), so they need the reistance of the idiot light.Generators are activited by changes in voltage, so the voltage regulator takes case of this and the idiot light does not.I think.
Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica RoadsterIf you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)
Sorry Paul, I’ve been away and am wrestling with serious health problems in the family (not mine).
But, as usual, when faced with a conumdrum, you can be counted upon to find the correct answer yourself. Well done! (or…I agree
with the results of your research)Thanks Roy. I don’t know if it’s well done either. 😉
But I have a VW powered TDr with a generator and a VW powered Intermeccanica Roadster with an alternator. I figure I need to understand them both!Paul Mossberg
Former Owner of a 1981 Classic Roadsters Ltd. Duchess (VW)
2005 Intermeccanica RoadsterIf you own a TDr and are not in the Registry, please go to https://tdreplica.com/forums/topic/mg-td-replica-registry/ and register (you need to copy and paste the link)
thanks for all the information.
wound up getting another generator,$50, from napa, with a 3 year warranty, and, just haven’t had time to install it.
coming soon, though.
After I had the Suby engine (with new Chinese alternator) in Bridget and running, I did not get any charging action at the Voltmeter. Turned out the idiot light circuit was not hooked up. The engine was running when I found that wire end and twisted it to ground. I could hear the engine sput under the sudden load the alternator gave it. The green light flashed on, then off, and the voltmeter went from 11.8 to 14.3 right away.
Since then it’s been weird, as I have discussed. But that idiot light did turn out to be crucial.well folks,
I was finally able to get back to the car, and, noticed that it has a red indicator, but, don’t know if it is for the generator, or, the bright lights.
hope to actually get started on it tomorrow evening.
well folks,
finally got around to tackling the generator. went to change it out, but, decided to do some more checking around, and, it turns out that the brush on the lower side of the generator was stuck.
took it out, to find that the bracket that it slides in and out of had been mashed down on the brush.
opened it up, so the brush would slide freely, cleaned both of them up, and, it charges great, so, i’ll be returning the one I bought.
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