ajg193 Posted January 25, 2021 Share Posted January 25, 2021 Who here is an alternator genius? On the Starlet I was looking at some data logs from a run today and noticed the battery voltage was down in the low 12s. It seems to have been doing this for a while. When the car first starts cold the voltage is fine, up just over 14 V. If I turn on the head lights or blower fan the voltage will drop down below 13. If I turn the loads off, the voltage will sometimes slowly creep back up to 14 but it seems more and more now it just stays low and keeps going lower. If I start the engine when it is hot the voltage will not get above 12.8 or so. Battery light isn't coming on. I pulled the cover off the voltage regulator and the points aren't opening or closing, it's just staying in one spot. The resistances in the voltage regulator test fine according to the repair manual. Any ideas what the problem is? Alternator finally had enough or something? Quote Link to comment Share on other sites More sharing options...
tortron Posted January 25, 2021 Share Posted January 25, 2021 Clean the points? The ones in my Morrie we're sticking. Cleaned them and that got got them functioning again Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 25, 2021 Share Posted January 25, 2021 Chuck it in the bin and replace with a modern internally regulated unit. You shouldn't be running that mechanical garbage with EFI anyways. 4 1 Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 25, 2021 Author Share Posted January 25, 2021 19 minutes ago, tortron said: Clean the points? The ones in my Morrie we're sticking. Cleaned them and that got got them functioning again Cleaning the points did nothing at all Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 25, 2021 Author Share Posted January 25, 2021 19 minutes ago, Yowzer said: Chuck it in the bin and replace with a modern internally regulated unit. You shouldn't be running that mechanical garbage with EFI anyways. I'm thinking that's probably going to be the route. The problem can be finding a replacement that actually fits the factory brackets. A lot of the aftermarket ones require KE20 brackets for some reason. Is there much work involved in bypassing the voltage regulator when going to an internally regulated unit? Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 25, 2021 Share Posted January 25, 2021 Surely the later EFI K series had internally reg'd alternators? And possibly different brackets. Shit, it's been awhile since I've converted them, but nah it's not difficult. Run L to your lamp, I to the ignition, S to the battery maybe, and Bob's your neighbours dog. 1 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 25, 2021 Share Posted January 25, 2021 I have quite a stack of alternators at work, if I get a chance I'll line them up and get a pic, ya might see one that may fit. They're all buggered in some way or another but at least ya can test fit it then either fix it or cross reference the part number to a new one. 1 Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 25, 2021 Author Share Posted January 25, 2021 I'll give the guys at oldscool autos a call after I pull the alternator out and test resistances/measure dimensions. /I'll put the dimensions up here to compare to your stack Quote Link to comment Share on other sites More sharing options...
NickJ Posted January 25, 2021 Share Posted January 25, 2021 Battery terminal hasn't come loose? Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 25, 2021 Author Share Posted January 25, 2021 Tight as a tiger Quote Link to comment Share on other sites More sharing options...
h4nd Posted January 25, 2021 Share Posted January 25, 2021 Woss the field current at? (Though I'm unsure what it actually should be). May give a clue to faulty brushes, field windings / alien electron eaters. Youd expect the relay to be on, and current to be climbing. Oh, and check output diodes 1 Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 25, 2021 Author Share Posted January 25, 2021 Pulled alternator off this morning and stripped it down/unsoldered the stator from the rectifier Rotor tests fine Stator coils test fine Rectifier tests buggered according to the specs in the book Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 25, 2021 Author Share Posted January 25, 2021 Bottom legs are 75 mm apart with clearance hole for M10 bolt Top leg is M8 Distance between top and bottom holes is 170 mm Pulley centre is about 30 mm from front face Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted January 25, 2021 Share Posted January 25, 2021 11 hours ago, Yowzer said: You shouldn't be running that mechanical garbage with EFI anyways. reasoning behind this? i just ran the externally regulated unit on the corona when i fitted the efi 18rgeu because it was easy and didnt seem to give any issues. but if its gonna cause long term issues id be keen to swap it out during the next engine build Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 25, 2021 Share Posted January 25, 2021 Electrical noise is one issue, the ecu should have noise suppression but it can still interfere with sensors, the other is current output as usually they're much more lower powered than modern alternators and you can suffer some voltage drop when running all the additional electrics that EFI requires. Quote Link to comment Share on other sites More sharing options...
Muncie Posted January 25, 2021 Share Posted January 25, 2021 A bigger alternator pulls less load too when its just cruising say 30% rated output where as a smaller alternator would be at 80% will be fair tugging on the belt. Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 28, 2021 Author Share Posted January 28, 2021 This is all resolved now. It appears the biggest issue was the fusible links (sections of wire designed to safely fail if overloaded) at the end of the +VE wire from alternator are old and couldn't cope with the current - resulting in large voltage drop and heat generation. I ran a new wire in parallel (auto sparky recommended as it can be difficult to remove the factory wire from loom) with the old one and put a 60 A fuse inline (a proper fusible link fuse). New wire is 7.92mm^2, rated for like 80 amps on a 2 metre stretch. Also threw a brand new alternator in for good measure as it was only $180. I think the old alternator is probably fine as testing the diodes with a diode tester indicated that they were still pretty much functional. So that's all soldered back together and stored away nicely in the new box. I tried a replacement voltage regulator (part number RGX2032), but the one I got was improperly calibrated at the factory and was providing more voltage than I was comfortable with - over 15 volts. Factory regulator is perfectly within spec so I returned the new regulator. I would still like to get one as a spare, preferably a solid state one though. 1 1 Quote Link to comment Share on other sites More sharing options...
Dell'orto Posted January 28, 2021 Share Posted January 28, 2021 1 hour ago, ajg193 said: This is all resolved now. It appears the biggest issue was the fusible links (sections of wire designed to safely fail if overloaded) at the end of the +VE wire from alternator are old and couldn't cope with the current - resulting in large voltage drop and heat generation. I ran a new wire in parallel (auto sparky recommended as it can be difficult to remove the factory wire from loom) with the old one and put a 60 A fuse inline (a proper fusible link fuse). New wire is 7.92mm^2, rated for like 80 amps on a 2 metre stretch. Was just going to post this - had the exact issue on a friend's KP, that old fusible link stuff turns to garbage with age. 1 Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 28, 2021 Author Share Posted January 28, 2021 My reckoning is that it was like that for years and I just never paid any attention to it. I did always notice how the temperature gauge would read slightly higher when the headlights were on even though the temp was actually exactly the same 1 Quote Link to comment Share on other sites More sharing options...
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