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John Kimbrough Member
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Did not see a subject directly addressing alternators so I thought I would start one. The behavior of my stock (and original) alternator has seemed to change over the last year or so. 1. Upon engine start, the guage, at idle, will read 15 volts, just at the edge of the red. 2. Then, on the road going through the gears with no headlights or other power users on it will then drop to somewhere in the 14-15 volt range. 3. When I turn on the headlights while on the road, the voltage drops a little, to 13-14 volts. 4. But at idle, with the lights on, the voltage drops to 10.5 volts. 5. If I then raise the engine rpm to about 2000 it comes back up to 13-14 volts very slowly. I am afraid that with the headlights and heater on, and the music playing, I may run out of juice. Anything to worry about? Is this normal? BTW, I did put solenoids in my headlight system and may be drawing more amps to them now. Thoughts? Thanks, John |
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Mark Rosenbaum Member 
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My car has a Delco unit, and I've never observed the behavior of a Lucas alternator, so my comments apply only to the former. I would expect the Delco and Lucas alternators to behave a bit differently in detail, but not in general. "1. Upon engine start, the guage, at idle, will read 15 volts, just at the edge of the red." * So does mine, once the alternator starts providing a charge. In my case, it takes 10-15 seconds for the gauge pointer to move from the bottom of the white band, to the top. I reckon a third to a half of this is due to the response time of the gauge itself. "2. Then, on the road going through the gears with no headlights or other power users on it will then drop to somewhere in the 14-15 volt range." * So does mine, over the course of 10-20 minutes of driving. I've been presuming that this occurs as the battery gets recharged. "3. When I turn on the headlights while on the road, the voltage drops a little, to 13-14 volts." * I see a slight drop but much less than a full volt's worth. I wouldn't think this is a problem. "4. But at idle, with the lights on, the voltage drops to 10.5 volts." * Not normal. Sounds like the alternator stops charging for some reason. For Delco alternators, I'd suspect dirty wiring connectors on the sense lines. For Lucas alternators, I'd suspect a bad internal regulator. * Is the 'Ignition' warning light on when this occurs? If not, the battery may have a bad cell in addition to any alternator problems. Also, some alternator types may not charge under some or all circumstances, if the warning light is burned out, or is an incorrect type. "5. If I then raise the engine rpm to about 2000 it comes back up to 13-14 volts very slowly." * It sounds like the alternator once again provides a charge at that time. This might be the normal response after your Case 4, depending on what you meant by 'very slowly.' I'd also check the battery terminals and cable ends to ensure bright metal to metal contact there. Whether Lucas or Delco, the alternator should be able to keep the battery charged under any plausible scenario. However, if one adds accessories that consume electrical power, the alternator's capabilities can easily be exceeded. If for example the car has a 60 watt sound system, you would need an additional 60 to 120 watts in additional alternator capacity -- that's 5 to 10 amps more. With a sound system that rattles windows on neighboring houses, you could be talking about needing an additional 40 amps or more. In theory, adding a couple of typical automotive relays to operate the headlights might make the difference between having some tiny current left over to charge the battery, and being slightly deficient, but in practice, relays don't use sufficient current to be a concern. For reference, I've attached the schematic of a typical Delco alternator (not necessarily the one used in the JH). Attachment: Delco SI schematic.jpg (Downloaded 108 times) |
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Judson Manning Member 
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The Lucas unit I have exhibits the same behavior as above. Keep in mind both alternators only put out a maximum of 30-35amps. Of course the question is: At what RPM??? As Mark mentions, start running a hot stereo, MSD ignintion, electric fan, and hook it up to a battery that only gets exercised once or twice a week; and sure, you'll have trouble maintaining 12-13VDC, especially at idle! Ron Earp and others have adapted newer alternators via custom brackets, but I'm sure a skilled alternator shop could re-wind either unit to output 60-90amps. |
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Jim DeClerck Member 
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Mark, Your diagram doesn't indicate the colors or the JH wiring diagram codes of the wires connected to the "#2 Sensing", "#1 Field" and "Bat" terminals of the alternator or which of the 3 terminals are the 2 larger ones vs the single smaller one. Can the 2 larger female spade connectors be attached interchangeably to the 2 larger male spade connectors? Also, the JH wiring diagram seems to show only 2 wires plus an uncoded ground (wire?) connected to the alternator. N-22-DB is connected to the battery junction and NY-31-SC passes through a 5 way junction en route via NY-42-SC to the ignition light. My alternator isn't charging and I'm trying to make sure of the connections. Thanks for any guidance you can offer. |
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Mark Rosenbaum Member
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My car has the stock Delco alternator. There are two plugs on its back: a big one with two heavy wires, and a smaller one with three wires of lesser size. I've attached an annotated photo of the wiring involved. The terminal numbers given in the photo are probably different from those in the alternator schematic posted earlier. Note that both the larger and smaller brown wires are connected to the battery. For the larger wire, this connection is at the battery junction in the middle of the battery cable. For the smaller wire, this connection is normally at the battery cable connection on the starter solenoid, but it could just as well go to the spare blade connector on the battery junction. I haven't bothered to figure out why the small brown / yellow wire loop is present, but IIRC the alternator didn't work properly when the wire broke off shortly after I bought the car, so I hooked things back up as shown. Attachment: Delco wiring annotated.JPG (Downloaded 117 times) |
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Jim DeClerck Member
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Thanks Mark, This car, 19336, has a Lucas alternator with 3 spade connectors on the back, 2 large spades (3/8") and one smaller spade(1/4"), and no failsafe plug to orient the wires. The PO did some electrical rewiring and I'm looking at 2 heavy gauge wires with 3/8" connectors and one thinner wire with an appropriately smaller (1/4") connector. I just found another note posted regarding on Lucas alternators in which Judson Manning answers the questions I had about connecting the wiring to the alternator, etc. The heavier wires with the 3/8" connectors are interchangeable on the two 3/8" alternator spades. One wire goes to the Battery Junction, the other wire goes to the starter solenoid (+) terminal. The lighter gauge wire with the 1/4" connector goes to the Engine Harness Junction (terminal 3) thence to the "IGNITION" light on the dash. This lighter wire brings current which acts to excite the field windings of the alternator. Apparently the Lucal alternator is grounded to the chassis via the mounting hardware. I never paid much attention to alternators/generators before as long as the belt was snug and the battery was charging. Thanks for sending the picture and advice. I'll save it in case the other car (Delco alternator) acts up. |
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Jim DeClerck Member
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A question from a non-electrician about the Lucas alternator field coil exciter wiring. This cable seems to be wired in series with the "Ignition" light bulb. If this bulb is removed or burns out is the alternator field no longer being excited and therefore will it bring a halt to alternator current being generated? Last edited on 05-16-2006 05:54 pm by Jim DeClerck |
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Mark Rosenbaum Member
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I'm not completely certain as I haven't worked with Lucas alternators, and a quick internet search wasn't much help. However, it appears that if the bulb is out or is bad, the alternator field may not receive any power when the engine is started, and if so, the alternator will never start charging. Certainly it can't hurt to have a good bulb there. |
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Jim Ketcham Member
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Mark is correct. If the bulb is out or fails the alternator will not provide a charge. |
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Jensen Healey Super Moderator 
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I removed the bulb several years ago but thankfully I have a Delco-Remy alternator. Kurt |
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Jim DeClerck Member
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This design feature of (later model?) Jensen Healeys leaves one wondering, "What were they thinking?". I assume earlier cars were equipped with Delco alternators and that later it was decided to change over to the Lucas unit. Is it known at which VIN. # they made the change? Is it feasible to connect a separate permanent cable from the battery +12v side to the Lucas 1/4" alternator exciter terminal to ensure charging of the battery without doing damage to other operations of the electrical system? Another question: I installed a good bulb (Peanut 2V) in the heater console light socket and it shines when I turn on the head lights. But when I check the voltage at the 1/4" female spade connector which would connect to the exciter spade on this Lucas alternator I get almost 0 current (0.03V). Shouldn't it be 12+ volts? Last edited on 05-17-2006 04:12 pm by Jim DeClerck |
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Greg Fletcher Administrator 
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Interesting about that, as I was recently thinking that same thing. Clearly, the car was originally designed to have the English Delco unit- it fits nicely everwhere with no fuss. The later Lucas unit barely clears the oil pump housing in the rear with the wiring plug in it and makes the installation process more work. The switch over does not appear to be consistent with the VIN either, but that's not a surprise since they appear to have often not left the factory in numbered order either. My old JH (13301) had the Delco unit installed originally and my current JH (13242) has the Lucas unit installed from the factory, so go figure. |
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Jim DeClerck Member
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My "early car", 14482 is equipped with the Delco. The Lucas unit is installed in the later car, 19336. Also, 19336 doesn't have a wiring plug, just 3 separate spade connectors. And the clearance is tight at the back of the alternator, as you say, and access is tricky. I'm hoping some electrical advisor can help with the questions in my previous post. 'Til then I'm kind of stuck. Now I wonder if it's possible that the exciter circuit will bring 12v to the alternator if all the wires are connected to the alternator and the engine is started. I'll try that next. |
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Mark Rosenbaum Member
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Jim DeClerck wrote: This design feature of (later model?) Jensen Healeys leaves one wondering, "What were they thinking?". I assume earlier cars were equipped with Delco alternators and that later it was decided to change over to the Lucas unit. Judging from what I see in the parts list and shop manual, it appears that Lotus provided engines with the alternator already installed. If so, then probably Lotus, not Jensen, was responsible for the change. Perhaps it was just a matter of British chauvinism, perhaps the Lucas part was cheaper, or perhaps Delco wouldn't sell alternators to Lotus for some reason -- hard to say at this late date. If I'm right, then the question should be, "at what engine number did they change from Delco to Lucas?" In this regard, the shop manual indicates a change from the 45 amp Lucas 18ACR to the 35 amp Lucas 17ACR alternator at engine number 9815. Is it feasible to connect a separate permanent cable from the battery +12v side to the Lucas 1/4" alternator exciter terminal to ensure charging of the battery without doing damage to other operations of the electrical system? Don't know. As mentioned earlier, I'm not familiar with the Lucas alternator. All I can suggest here is to try it with a temporary hookup. If things work, make the wiring change permanent. If not, you're probably no worse off, though I suppose it's conceivable that the alternator might be damaged as a result. Another question: I installed a good bulb (Peanut 2V) in the heater console light socket and it shines when I turn on the head lights. But when I check the voltage at the 1/4" female spade connector which would connect to the exciter spade on this Lucas alternator I get almost 0 current (0.03V). Shouldn't it be 12+ volts? The IGNITION light on the heater console should illuminate only when the ignition switch is in the RUN position and the alternator is not providing a charge. The status of the headlights should not affect this at all. You may have a previously unsuspected wiring fault. The bulb itself needs to have about 6 volts across it to illuminate dimly, and 12 volts normally, so 12 volts on one side and 0.03 volts on the other is to be expected. The 0.03 volts is the alternator's output voltage at this time. When the alternator begins to function, its output quickly reaches then slightly exceeds the battery voltage. This normally happens so quickly that the bulb filament is still hot and producing light even though there is very little voltage across it. And finally, when that occurs, the bulb rapidly cools off and extinguishes. If all else fails, your local Kragen auto parts store probably has the ability to test it for you. This is generally free, either as a matter of promoting customer good will, or because they think you might buy a replacement from them should you need one. |
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Jim DeClerck Member
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I've traced the wires and found the reason my alternator was not receiving 12v to excite the field coil. The socket for the IGNITION light had been repaired by some PO and in soldering the NY (brown and yellow) wire to the back of the socket they had caused heat damage to and partially melted the plastic inner contact carrier such that the bulb's base was no longer able to touch the metal center. Current could not flow through the bulb and complete its journey from the fuse box to the alternator. A new light socket is on the way from Delta. Thanks for all the thoughtful replies to my plea for help. |
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Jim DeClerck Member
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Mark, In rereading your note I see that there was a change from the Lucas 45 amp alternator to a Lucas 35 amp unit at engine number 9815. Is there any indication in your reference showing the engine number for a change from Lucas to Delco alternators or vice versa? Last edited on 05-30-2006 03:43 pm by Jim DeClerck |
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Mark Rosenbaum Member
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Jim, Sorry, I've never seen anything that documents when the change from Delco to first Lucas alternator occurred. Greg's comment that his second car, a late MkI, has a factory-provided Lucas alternator suggests that Lotus bought both Delco and Lucas alternators, and installed whichever was in stock on any particular day. Manufacturers like having multiple sources for essential parts. |
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Jim DeClerck Member
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Update to my 5/26 note: I installed the new ignition lamp socket and bulb which, with the ignition switch on, permits current to flow through the Lucas alternator exciter wire and provide 12v to the alternator's small spade connector. Now the ignition light lights and there is 12v at the alternator end of the exciter wire. So far, so good. All else being OK, when I start the engine, the ignition light should go out and the alternator should charge the battery. Neither happens. I took the alternator to my local Auto Zone where it was put on the testing machine and was pronounced to be OK. I'm going to have a test done at another shop and get a second opinion. The PO did some wiring rerouting and shielding so there may be a problem with that. Why can't guys leave well enough alone??? |
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Paul Koehler Member 
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For an excellent read on alternators and things electrical, spend some time at:http://www.madelectrical.com. PK |
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Jim DeClerck Member
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Life is now good! I took my Lucas alternator from 19336 for test and/or rebuild today. The Huntington Beach shop tech opened it up, found that a wire end had come adrift from its solder joint connector, resoldered the connection and, like magic, no more intermittant charging/not charging issues! It produced 14 volts and 35 amps. On two previous occasions different shops had tested it good (AutoZone) and bad (Kragen), respectively. When the loose wire touched its connector it tested good and vice versa. When it was in the car it would not charge. That's the second instance of a failed JH solder connection. The other was in a several wire junction portion of the wiring harness under the dash that supplies the headlights, etc., with current. Now on with other parts of the restoration project. |
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Joel Member
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Despite the title of the thread (Stock, replacements, conversions) I don't see any info on replacements. Mine is undercharging at low RPMS and overcharging at speed. I have 2 spares - both Delco - the running car is a Lucas. Go figure. So, is there a simple replacement? I'm planning to find a shop to repair it tomorrow but if there's a simple, off the shelf, better quality (ummm Bosch?), replacement, I'd rather go for that. Happy 4th. |
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jgreen Member
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Joel, My JH uses a Bosch AL300X which has proven to be very reliable. I am not sure of Lucas wiring on the alternator but I can send a JPEG of my alternator wiring hook up in the rear if you need it, tomorrow. John |
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Joel Member
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Thank you sir! I'd appeciate the JPEG. The Delco unit has 2 separate plugs. The Lucas has 3 spade connectors. I can't see dinking around to figure out the difference just to use the spare I have. It's worth 100 bucks for a rebuild just to not have to trace wires. . . |
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Dan (Florida) Member
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I had troubles with the stock alternator on 19444 and obtaining rebuilds from my supplier in Florida was getting worse so I took their advice and adapted the common Delco single wire alternator that is prevalent in most GM cars. It requires only a single connection (the heavy brown wire) to the battery and is commonly replaceable at any parts store. It is also around 85 amps output so it should provide for any needs. It mounted easily ( see photos in the Florida car gallery) and doesn't require an exiter curcuit, so no bulb. I have noticed some unusual voltage drops after highway drives, but overall has been reliable. At $75 for a rebuilt unit I have no complaints. hth Dan |
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Judson Manning Member
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Dan, From which GM cars is your replacement alternator sourced? Judson |
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Dan (Florida) Member
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I'm not sure, he stated it was a very common alternator to most GM cars of the last decade. I just made sure it turned the right direction. It only has one terminal on the back an was a snap to install Dan |
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Ron Earp Member 
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I'd bet it is a GM 10si one wire style. I use the GM 10si one wire type on all the race cars we do. My Jensen does not have a 10si though, but it should. I have some Powermaster deal on there that isn't perfect. Judson you can make a 10si fit easily, you'll just need to tweek a bracket and using some spacers (washers) to make it go on, but it'll go on. Cheap, plentiful, and durable plus the one wire deal makes them simple. R Last edited on 07-08-2007 12:36 am by Ron Earp |
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Judson Manning Member
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Thanks Ron, Not really interested in having to fab a set of brackets like you had to do on the ITS car. Maybe the 10si is the trick. From my junk-yard recon it seems the 240SX alternator could also fit with just spacers. Judson |
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Ron Earp Member
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!0si case is similar, easy fit. Put one on my Z in place of the Z alternator which is not so easy to get at a store. I wanted something I could buy anywhere, anytime. The Powermaster I have the ITS car is okay, but it was supposed to be a 10si case style to and turned out not to be. It came with brakets I modified and was easily put on. I probably should have sent it back to Summit but I just made do. It is small, and works well when everything is in place correctly. 10si is the way to go I think. |
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