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After sorting the AAV issue over the weekend and enjoying the fruits of my labor with a fantastic cruise to the beach with the family on a beautiful summer's day, today a new issue presents itself.
After returning to the car this evening after work, started her up, and noticed that the battery gauge was showing well below the midline. Normally even with the headlights on, the needle on the gauge sit's on or just below the line. Drove her home with no issues, but the needle on the gauge didn't move (with the exception of when using the turn signals, where the needle did its normal up and down dance, but just lower on the gauge than usual).
After getting home, turned the car off and let it sit, restarted, and the same issue. Measured the voltage using one of those digital voltmeters that plugs into the cigarette lighter, came out as 12.3v with the car idling, and dropped to 12.0v with the headlights/radio on.
In addition to this, the alternator warning light is on, and proceeds to stay on even after the car has been shut off, keys out.
Any one have any ideas as to where to start with resolving this issue?
Here are a couple of pictures I took of the gauge and warning lights:
First thought is that the Lucas alternator has dropped a diode to earth.
That would explain the light ON with the car asleep, and also the lack of charging.
The dancing of the volt gauge with the indicators is a very bad earth in that charging circuit, and that bad earth may have led to the altrnator Fritz.
The volts you have recorded with the DVM is simply battery voltage.
As a poke in the eye check, reach down and unplug the SMALL wire from the alternator. Insert the Red lead of the DVM insto the terminal at that wire. Place the Black probe on any convenient earth point, and turn ON the Ignition, No need to start the engine. Note the volts in that wire, it should be battey voltage.
My reason is that the age of thst car may be getting to an Ignition switch electrical section going flaky. Quite common, but I doubt it really, coz the engine runs, but you have to check as a 1st step.
That thin wire you just unplugged is notorious for breaking, and the terminal is also known to part company with said wire, hence the Volt light and NO charge, ya might be lucky.
First thought is that the Lucas alternator has dropped a diode to earth.
That would explain the light ON with the car asleep, and also the lack of charging.
The dancing of the volt gauge with the indicators is a very bad earth in that charging circuit, and that bad earth may have led to the altrnator Fritz.
The volts you have recorded with the DVM is simply battery voltage.
As a poke in the eye check, reach down and unplug the SMALL wire from the alternator. Insert the Red lead of the DVM insto the terminal at that wire. Place the Black probe on any convenient earth point, and turn ON the Ignition, No need to start the engine. Note the volts in that wire, it should be battey voltage.
My reason is that the age of thst car may be getting to an Ignition switch electrical section going flaky. Quite common, but I doubt it really, coz the engine runs, but you have to check as a 1st step.
That thin wire you just unplugged is notorious for breaking, and the terminal is also known to part company with said wire, hence the Volt light and NO charge, ya might be lucky.
I'll get on it first thing in the morning. Just my luck that I have a rostered day off tomorrow. The Lord giveth a day off, the Lord taketh my alternator, haha. I'll keep the forum posted!
So, measured the voltage across the terminal mentioned in your original advice and the earth point and switched the key to IGN, and read just under 12v on the voltmeter. The wire itself was still attached and in decent condition.
Dad and I swapped out the alternator for one that we had removed from the other car, and the good news is that the alternator warning light is no longer on when the car is off. The bad news is that the alternator warning light is on when the car is on, and the charge gauge on the dash shows the needle now on the top of the red section. The alternator seems in decent condition, the brushes are still good.
Based on the information I was reading about in the other alternator warning light thread, and a previous issue we had last year where the light came on and I had zero charge (ie. the needle was dead at the bottom) that was rectified by replacing the regulator on the alternator for a new one, might seem like another regulator is required?
Buggered if I can find any onshore though. The guy I got the last one from on ebay has apparently been out of stock for a while, and Jag Spares have got one for 75.00. Might have to bite the bullet and buy a stack of them from the UK for that pricea nd ship them over, and have a bunch spare (or to sell on to recoup my costs).
I had my alternator rebuilt for $110, $75 seems a bit high for regulator.
Just get a Bosch regulator it will work and about $45.00
Might also be worth upgrading to a 110amp alternator, I think the early XJS alt is way too small.
Thanks for the reply, Warrjon!
Yeah, considering the last replacement voltage regulator I purchased for the XJS only set me back about $20 incl. postage, I didn't think that $75 would be something I was willing to part with.
With the alternator upgrade to the 110amp, I take it that it will not be a straightforward swap with the old unit? I'd love the simplicity of using a more modern, local unit with more juice, but from what I've read I'll need to fabricate or modify the mount for the alternator, and possibly also need to swap over the pulley, correct?
1) Those Lucas alternators are lazy suckers at best. Sometimes they take a bit to get "excited", soooooo, start the beast, give the throttle a quick "blip" to 2000rpm, and see if the alternator "kicks in". You will hear it, and see the gauge start to rise, BUT, those dash gauges are just as lazy, so, again, put your DVM accross the battery and note the voltage before and after the "blip".
2) The upgrade uses an XJ40 Bosch unit, with a V pulley fitted. Phil, at H&H Prestige supplied mine years ago, and the long thru mounting bolt included, and the V pulley ready fitted. The alloy mount on the engine needs to come off, and the hole drilled to 10mm from 8mm, SIMPLE.
I had a problem with similar symptoms and as you have done replaced the alternator (twice) without any success. Eventually traced the problem to a failed 'Load Dump Module' connected to the alternator and located on the RHS inside guard - see enclosed diagram. It is a small black plastic box about 30mm square. Replaced that and alternator was charging again and no red lights.
Location of 'Load Dump Module'
1) Those Lucas alternators are lazy suckers at best. Sometimes they take a bit to get "excited", soooooo, start the beast, give the throttle a quick "blip" to 2000rpm, and see if the alternator "kicks in". You will hear it, and see the gauge start to rise, BUT, those dash gauges are just as lazy, so, again, put your DVM accross the battery and note the voltage before and after the "blip".
2) The upgrade uses an XJ40 Bosch unit, with a V pulley fitted. Phil, at H&H Prestige supplied mine years ago, and the long thru mounting bolt included, and the V pulley ready fitted. The alloy mount on the engine needs to come off, and the hole drilled to 10mm from 8mm, SIMPLE.
Looks like long term I'll have to do the upgrade to the XJ40 unit, so I'll be keeping eye out on the old ebay and gumtree for people parting out their cars. Overall from your write up, it looks more time consuming than complicated, that I can deal with.
Gave the other unit we put in the rev test and getting nothing.
Until such time that I can source a reasonably priced XJ40 unit, I've been looking at the current Lucas alternator on the workbench, and figure for the most part from everything I've read, it's not the unit that ultimately fails but the regulator within the unit. As simplistic as this is, the replacement procedure is a royal PITA.
Could it be possible to modify the connectors within the alternator that go to the regulator, with extension wires, so that the regulator can be mounted externally from the alternator, say on the inside wall of the engine bay?
1. Remove the regulator from inside the alternator.
2. Reinstall the alternator with extension wires for the connection of the regulator.
3. Mount the regulator to the inside wall of the engine bay.
4. Connect the regulator to the extension wires to the alternator using one of those 2-pin socket connector things.
In theory, this would make it so much easier to just swap out regulators when they fail, as opposed to having to go through the whole process of removing and reinstalling the alternator unit itself. I've probably missed something here and oversimplified things, so are there any issues that could arise from this?
I'm not familiar with 75amp alternator and have never seen one, but I can tell you if the regulators keep failing then either the regulator is under sized or the heatsinking is poor. Oil buildup on the alternator will reduce cooling and cause regulator failure.
The better the heatsink the higher the current capability of the regulator. So a smaller regulator on a better heat sink will have better current capacity than a larger regulator on no heatsink.
Your idea to remote mount is a good one as long as the wiring to and from the regulator is secured so it CAN NOT short on the car, ie tied down and triple insulated.
You could also try mounting the regulator on an aluminium bracket on the rear of the alternator. Getting the reg out of the alternator and into air flow on an aluminium bracket may solve the problem.
You are really stretching my memory, but YES. I did it way back on the Daimler, and used a standard RE55 regulatror.
That car had the Motorola unit, and Regs were simply not available, so went feral with it.
I agree also, Lucas Regs were installed in such a manner that fiddling was near impossible, unlike the Bosch plug and play system, and waaaaay back in the late '70's, when I worked for Lucas here at Gepps Cross, the regulators were the WEAKEST part of any Lucas alternator, very, very fragile bits of junk.
when I worked for Lucas here at Gepps Cross, the regulators were the WEAKEST part of any Lucas alternator, very, very fragile bits of junk.
Too right. My car ate OEM Lucas alternators for years until I fitted a 115 amp rebuilt unit from an independent specialist. From then on the volts were at 14+ and never a problem since in 6 or 7 years.
Greg
In addition to this, the alternator warning light is on, and proceeds to stay on even after the car has been shut off, keys out.
To clarify....
You have two warning lamps associated with the charging system. Is it ONLY the 'lightening bolt' warning lamp, as you've shown in your first posting, that stays on? Or is it also the conventional battery warning lamp as well, as seen in the pic below?
The lightening bolt lamp is controlled by the 'over voltage unit'. This is very clearly shown in the wiring diagrams. I don't know how it works but it's apparently a voltage sensing device. It takes a voltage reading from the ignition switch. No actual tie-in to the charging system.
*IF* the conventional battery/charging light is NOT on, and the over-voltage light IS on, coupled with your obviously low system voltage..... I have a nagging feeling that there's something else afoot here.
I had a problem with similar symptoms and as you have done replaced the alternator (twice) without any success. Eventually traced the problem to a failed 'Load Dump Module' connected to the alternator and located on the RHS inside guard - see enclosed diagram.
Good thought....seems like bypassing/removing it is the typical 'fix'. But I'm not sure if it's applicable here, as not all models have one
The dump module was installed circa 1989 as I recall. I think we're talking about an '87 in this case. The dump module is not shown in the earlier (1987-older) diagrams
*IF* the conventional battery/charging light is NOT on, and the over-voltage light IS on, coupled with your obviously low system voltage..... I have a nagging feeling that there's something else afoot here.
Hi Doug,
The issue originally was that the battery warning light was not on. However the lightning/alternator light was on, when the engine was off, and the key out. The voltage gauge was well below the midline, and I assume that was only reflective of the current battery voltage, which would decrease as the battery would run out of charge.
I did think the lightning bolt warning light was triggered by any issues to do with the alternator charging, whether it be over-charging or under-charging, outside of a given range that is governed by some sensor. I wasn't aware that it was only to indicate over-charging?
We had replaced the alternator with another unit we had lying around (same Lucas part) since then. Lightning bolt warning light is now off when the car is off (whether the key is in or not), but comes on and stays on when the key is set to the IGN or when the car is started. Voltage gauge is still only reflecting the current battery voltage, and decreases when the charge in the battery decreases.
Normally I would say the chances of having two bum alternators would be pretty slim, but given that they're both used, old, Lucas units, I certainly wouldn't be surprised. I now have 10 new regulators for the Lucas en route from the UK, since I can't seem to find the part (or a compatible alternative) here in Aus (at least at a reasonable price), so for the price of the one that I was able to find on offer, I was able to get my hands on a stack. Hopefully that's all I need to get the issue sorted.
Last edited by ThunderRoad; 03-05-2017 at 08:47 PM.
Is it operational at all? With the key turned 'on', but not turned to 'start', does it come on?
Cheers
DD
Sorry mate, I wasn't very clear with what I was trying to type, haha, got them Monday blues at work.
What I meant is that the battery warning light was never an issue. Before the alternator issues, it turned on when the key was put in and the car started, and then turned off after a few seconds. Now, with the alternator issues, it still does the same thing.
02-27-2017, 06:18 AM
Alternator warning light?
