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Apr 10, 2022 17:26:54 GMT
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I've been having trouble with the output from my alternator. When I start the car, it'll show around 14.5 on the Crypton analyser for the alternator output test, but after about 30 or 45 seconds (a short time, basically) it drops to around 13v and a little below sometimes, then the warning light is on dimly. Sometimes it will pick itself up and go back up to a higher output, then it'll drop again. I've stripped the alternator and there was a bit of rust on the centre rotating part which I cleaned off, and the same on the outer ring, which I also cleaned off. The brushes are almost new, the whole thing is very clean. When I first put it back together, I'd put a little bit of grease in the lower roller bearing as I thought it might help, and some of that had come off and got onto the brushes. I stripped it down again, cleaned off the excess grease, cleaned the brushes and slip rings with contact cleaner, but it's not really helped. This is the trace on the Crypton scope, which doesn't look anything like the even trace that the manual suggests it should be. It could be an issue with the scope, although it's been OK in the past. Any ideas what might be causing this problem? It's weird (to me) that it comes and goes.
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Last Edit: Apr 10, 2022 17:27:21 GMT by droopsnoot
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Apr 11, 2022 18:55:26 GMT
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I had something similar when the main power wire from the alternator was loose at the starter solenoid.
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Apr 11, 2022 19:42:06 GMT
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I would load test the alternator diodes individually by passing a small current through them from a torch or such like.
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I had something similar when the main power wire from the alternator was loose at the starter solenoid. I have checked at the alternator end, but not at the starter end - I will have a look at that. I would load test the alternator diodes individually by passing a small current through them from a torch or such like. I'm not exactly sure how to do that, so I'll do a bit of reading on it.
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Not an alternator (or even electrickery) expert by any means. BUT, your symptoms sound identical to mine, which turned out to be a dud diode in the rectifier. Juuuuust about worked when cold, but the heat either expanded something away and broke contact or messed with the gubbins of the diode just enough to produce a drop in voltage and a feeble flicker from the charge warning light.
Took it to a little man-in-a-shed type starter alternator place and had it fully rebuilt with new bearings and the like for about 40-50 quid.
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Apr 12, 2022 17:06:39 GMT
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I've had another look at this today. First off the list was a loose connection at the starter, which is a relief as I'd have felt a little daft to have missed something like that.
I've swapped a few things with another alternator this afternoon, and got varying results out of it. I've also managed to break a little off one of the carbon brushes, which can't help. The problem is that the other alternator is of uncertain heritage, so I might be swapping iffy components for worse ones.
On the plus side, I can get the alternator out, on to the bench and stripped down in under ten minutes now.
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squonk
Part of things
Posts: 855
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The trace on the scope should be a smooth flat line for a dc output from an alternator with maybe just a tiny hint of ripple. The fact that it is a regular jagged shape shows that there is ac content in the voltage being measured. The diodes in an alternator rectify the ac output of the to give a dc output. So the trace is actually showing you that one of the diodes is not doing its job properly.
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2004 Chevrolet Avalanche Z71 2005 Mercedes CLK320 Cabriolet 1996 Mercedes C180 Elegance Auto Saloon 1996 Rover 620Ti (Dead fuel pump) 1992 Toyota HiLux Surf 1987 Range Rover Vogue (Rusty) 1992 Range Rover Vogue SE (More Rusty) 2006 Chrysler Grand Voyager 2008 Corsa 1.4 Design
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Apr 13, 2022 17:19:05 GMT
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I understand what you mean, however this is the trace that the Crypton manual says should be shown on the scope: Yesterday I changed first the diode trio, and then the rectifier, from another alternator, without any success, swapping each item back as it proved to not be any better. Today I have changed the regulator, and the alternator is now charging correctly, showing up to 15v when the engine is running. The scope display is still the same, so the fact that it's not as regular as the manual shows suggests that there may be an issue with the scope. I can't explain why the manual doesn't suggest it should be an almost-flat line.
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squonk
Part of things
Posts: 855
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Looks like the Crypton is measuring in ac mode. The trace randomly dropping off in your picture suggests that the regulator was occasionally dropping out and coming back again. If the scope were measuring in dc mode the line would be flat with a step change visible when the voltage fluctuates. In many cases it helps to be able to measure an electrical signal in both ac and dc modes when hunting down an electrical fault. You may find this article interesting: www.brighthubengineering.com/consumer-appliances-electronics/83694-how-to-test-an-alternator-with-an-oscilloscope/
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2004 Chevrolet Avalanche Z71 2005 Mercedes CLK320 Cabriolet 1996 Mercedes C180 Elegance Auto Saloon 1996 Rover 620Ti (Dead fuel pump) 1992 Toyota HiLux Surf 1987 Range Rover Vogue (Rusty) 1992 Range Rover Vogue SE (More Rusty) 2006 Chrysler Grand Voyager 2008 Corsa 1.4 Design
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Apr 14, 2022 14:03:35 GMT
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Which alternator, Lucas or Delco? Ive quite a few new old stock components for them
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Apr 14, 2022 16:58:41 GMT
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Which alternator, Lucas or Delco? Ive quite a few new old stock components for them It's the Delco alternator. To add to things, it's actually got a Lucas sticker on it, but I think that means that it was refurbished by them. I'll send you a PM over the weekend, I've got a couple of the same type it would be handy to fix up.
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Apr 24, 2022 17:33:59 GMT
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I'm not sure this is quite fixed yet. I've been out in the car today to a local morning event, and noticed several times that the battery gauge on the dash is dropping well below the half-way point, to an extent that I had range anxiety wondering if I was going to get home before the battery dropped - just like driving an EV but without the quiet. Then, it would pick up again and read into the normal area.
I haven't done any fault finding yet, as I had other things to attend to this afternoon. But there may be more random swapping of parts on the cards.
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Ah. Before I started delving into this yesterday, I remembered that I had a similar thing happen on the Firenza a few years ago while leaving a show - the battery gauge started dropping as I frantically unplugged the satnav and switched off anything I didn't need. No warning light on, though, even just a little.
That turned out to be a loose spade connector on the gauge, and I think this is the same problem. I've squeezed up the connector and re-fitted it, it's a much better fit now and I need to find time to road test it to see if I've actually fixed it or whether it's just another red herring.
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Jun 12, 2022 17:26:41 GMT
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This seems to be rearing it's ugly head again. I took the car to Tatton Park last weekend, it was fine all the way there (~22 miles) but as I drove up the driveway the battery light came on faintly and the gauge started dropping. I switched the headlights on, the warning light went out and the gauge went up again. At the end of the day it did the same on the way out, when the engine was still cold, again as I drove to the nearby town (went out by switching on the lights) and was then fine all the way home.
I had a look around the wiring, saw that the main connector is perhaps a little "iffy", swapped it hoping that I'd tracked down the issue, but I hadn't. Today, I've put a different alternator on the car, the output is down from 15.2v to 14.7v but the light seems to have stayed out while I had the car running and while I was checking out other stuff. It's not much of a test, but on the previous one it had come on fairly quickly today. So maybe it's fixed.
Could the relatively high output be causing a problem?
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melle
South West
It'll come out in the wash.
Posts: 1,981
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Jun 12, 2022 18:18:51 GMT
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My Saab 900 had similar intermittent symptoms a good few years ago, that lasted for about a year. In my case also switching the lights off and on again usually helped (I lived in Denmark at the time where it's mandatory to have the headlights on at all times). Went through a lot of fault finding trouble, fitted a refurbished alternator but that didn't solve the problem. Eventually I broke down on the German Autobahn (in the outer lane, but in a traffic jam fortunately) and was recovered to a local Saab dealer. Before I opened the bonnet the chap asked if I had already checked the main earth point for corrosion. When I replied 'no', he said something to the effect of 'OK, then I can guarantee you that the lead between the starter an the alternator has finally melted', and he was right. Fixed in 10 mins, followed by an extensive tour of their restoration (Bugattis, Porsches etc) and race & rally (Saabs!) department as a bonus, and it only cost me a few beers and a fiver for a second hand lead. Never had an issue since!
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www.saabv4.com'70 Saab 96 V4 "The Devil's Own V4" '77 Saab 95 V4 van conversion project '88 Saab 900i 8V
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I've been looking through the various connections as kevins mentioned them earlier, and I'd checked everything except this large power output connector. Certainly the starter end of the positive wire is good and solid, and the alternator grounds through the mounting to the engine. I hate intermittent faults, just not knowing of or when they'll pop up again. I didn't want it to be something as simple as a loose connection (I rebuilt the car, and the loom, and I'd to have overlooked something like that) but right now I'd just settle for finding something. As I'm swapping bits for other bits that aren't known working bits, I guess it's pot luck whether it will go away. But there's no point having a load of alternators on the shelf and then just buying a new one as soon as it looks like the one on the car might be playing up.
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Jun 14, 2022 12:32:41 GMT
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Wasnt there a bit in that alternator manual about curing the problem with an intermittent warning lamp?
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Jun 14, 2022 17:16:13 GMT
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Sort-of, though I wouldn't have described this as "flickering" - when it comes on, it's on, but dim. And the alternator output did seem to be dropping, too, though I'm not sure how the Crypton can distinguish between the alternator output and the battery voltage. It just seems to me that it's not quite the same situation - that workaround is for when the alternator output is good, but the light still flickers.
It does seem, though, that the supplementary harness is just joining the indicator and battery wires together, which seems a bit of a work-around rather than a cure. But it's worth keeping in mind if it's still causing trouble.
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jimi
Club Retro Rides Member
Posts: 1,777
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Today, I've put a different alternator on the car, the output is down from 15.2v to 14.7v but the light seems to have stayed out while I had the car running and while I was checking out other stuff. 15.2 is on the high side, 14.7 is normal. What are you measuring the voltage with ?
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Black is not a colour ! .... Its the absence of colour
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