Nigel A Posted September 2, 2018 Report Share Posted September 2, 2018 I have a 45 amp alternator with a voltmeter fitted but have a bit of a worry Most of the time it reads 13.5 volts At 2000 revs With Revotec fan running it drops to just under 13 volts With headlamps (Osram night breakers) on as well it drops to just over 12 volts At idle with everything on it reads just under 12 volts Is this normal? Im in a quandary as we are off to Angouleme very soon and returning via the Italian lakes and Switzerland, so a lot of driving in the Alps. Do I Leave it as it is Buy an 18 ACR alternator (45 amps) from Moss tomorrow Fit a 55 amp alternator If the latter where is the best and quickest place to purchase one that will be a direct swap. Thanks for your help Nigel Quote Link to post Share on other sites
Steves_TR6 Posted September 2, 2018 Report Share Posted September 2, 2018 I had similar low voltages on my car Nigel, a new alternator perked them up nicely. I bought from one of the suppliers on ebay, could look out his name if it helps? It was a 45a alternator, but the seller stated that they can actually deliver closer to 50, which should be plenty. My car had a new battery fitted the day i bought it, as it wouldnt start!, a halfords Calcium jobbie that has been fantastic for the 6 years i’ve had the car, even with the lowish voltages. Steve Quote Link to post Share on other sites
Steves_TR6 Posted September 2, 2018 Report Share Posted September 2, 2018 Ps, i wouldnt trust the voltmeter for actual readings, more for its relative position when running, idling, lights on etc. These gauges work by bending a bimetallic strip wit a pointer attached, neither precise nor accurate after 40 years ! Quote Link to post Share on other sites
Steves_TR6 Posted September 2, 2018 Report Share Posted September 2, 2018 Here’s the link to ebay item if you need it, very cheap ! https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F382402518084 Quote Link to post Share on other sites
Nigel A Posted September 2, 2018 Author Report Share Posted September 2, 2018 Thanks Steve for the info, they are now stating it is nearer 60 Amps, excellent price and I can collect locally too. Did it fit without any modifications and is the pulley the correct size. I have the biggest Varta battery that would fit, and the loom is a custom job from Advance Autowire in the States so can cope with the increased amperage. The voltmeter was new about 6 years ago. Looking for a simple fix so close to the off. Nigel Quote Link to post Share on other sites
Waldi Posted September 2, 2018 Report Share Posted September 2, 2018 Are these very cheap but brand new alternators reliable? A reconditioned oem Bosch will cost 90-100 euro, it is a straight fit. But this is a new item. Any experiences on these cheap reproduction items, good and bad please? Waldi Quote Link to post Share on other sites
Steves_TR6 Posted September 2, 2018 Report Share Posted September 2, 2018 I’ve had that alternator on for about a year, straight fit and no problems at all so far. The seller is an MGB specialist....... maybe MGB owners are more price sensitive than us ! Quote Link to post Share on other sites
Nigel A Posted September 2, 2018 Author Report Share Posted September 2, 2018 Just had another look at their advert and long delivery time! I will phone them tomorrow and see if they can take orders over the phone with next day delivery. In the meantime does anyone know of any other reliable sources Nigel Quote Link to post Share on other sites
Fireman049 Posted September 2, 2018 Report Share Posted September 2, 2018 Hi Nigel ~ Here's a handy tip for ease of fitting your new alternator. The rear bolt is a swine to try and get a spanner on the inside under the alternator. I fabricated two plain washers which will hold the head of the bolt steady as you tighten the securing nut. These photo's show how it all works ~ Simples!! Cheers ~ Tom. Quote Link to post Share on other sites
Nigel A Posted September 2, 2018 Author Report Share Posted September 2, 2018 Hi Tom That’s very clever Really impressed Nigel Quote Link to post Share on other sites
Fireman049 Posted September 2, 2018 Report Share Posted September 2, 2018 You're very welcome Nigel. If there's anything else I can help you with them please PM me. Best regards ~Tom. Quote Link to post Share on other sites
iain Posted September 2, 2018 Report Share Posted September 2, 2018 Brilliant Tom! So simple. Iain Quote Link to post Share on other sites
Fireman049 Posted September 2, 2018 Report Share Posted September 2, 2018 Thank you Iain ~ Tom. Quote Link to post Share on other sites
Lebro Posted September 2, 2018 Report Share Posted September 2, 2018 Before you rush out to replace the alternator I would check the battery voltages with a more accurate meter. Bob. Quote Link to post Share on other sites
Nigel A Posted September 2, 2018 Author Report Share Posted September 2, 2018 (edited) Hi Bob Thats a good suggestion, Worried I wouldnt get it in time so I have ordered a new one updated to 50A from ATP for collection from Argos on Wednesday. In the meantime I will check the battery voltages and I can then return the Alternator if necessary. If they prove to be fairly close, could this point to the battery or is my first thought that it is the alternator correct? Checked the actual website of the company that Steve suggested but unfortunately they cannot do a quicker delivery, so couldnt take the risk even though I prefer to follow others recommendations Nigel Edited September 2, 2018 by Nigel A Quote Link to post Share on other sites
Lebro Posted September 3, 2018 Report Share Posted September 3, 2018 If the car starts ok i.e the starter motor spins fairly briskly, & does not fade after a few seconds, then the battery is probably OK. Try charging the battery from a mains charger overnight, then check the voltage (while still on charge) is should be around 14 - 14.8. Then run the car, & check again at revs above 3000 - again should go up to 14.5 - 14.8 if alternator is OK. Bob. Quote Link to post Share on other sites
aardvark Posted September 3, 2018 Report Share Posted September 3, 2018 There is a really useful YouTube video from moss motors for checking alternators (I watched it last night!). I cant post a link but it was pretty easy to find. On youtube, search moss motors, click on videos then scroll down. Its near the top of the videos. Cheers Dave Quote Link to post Share on other sites
Nigel A Posted September 3, 2018 Author Report Share Posted September 3, 2018 Thanks for the help Bob, I’ll carry out the checks on Wednesday when I’ll have a free day to work on the car. I hadn’t thought of YouTube Dave, I’ll have a hunt for the video whilst queuing at Heathrow today. Thanks Nigel Quote Link to post Share on other sites
RobH Posted September 3, 2018 Report Share Posted September 3, 2018 Nigel - the load you are describing (fan plus headlights) could easily be 20 amps or more and at that current It only takes 75 milli-Ohms in a poor connection to drop the 1.5 volts or so that you are seeing on the dashboard meter. Before suspecting an alternator fault it would be worth checking all the high-current connections from the alternator back for cleanliness and tightness. Most alternators are 'machine sensing' which means they regulate to keep the voltage at the output terminal constant and cannot not compensate for poor connections downstream of that. Quote Link to post Share on other sites
Lebro Posted September 3, 2018 Report Share Posted September 3, 2018 +1 Quote Link to post Share on other sites
Nigel A Posted September 5, 2018 Author Report Share Posted September 5, 2018 Result!! After many years of sorting out all electrical problems with a bulb and 2 pieces of wire I finally bought a multimeter. I followed through the step by step instructions on YouTube and the voltage with everything on was 12.01v Fitted the new alternator which according to the test results has a max output of 57 amps, the only problem was the top mounting which had a metric thread. With everything on, according to the multimeter it hardly moves from 14.2 v. The voltmeter on the dashboard is also pretty steady but reads about 1 volt low. It was a cheap replica, so I quess I got what I paid for and will just have to live with it for now. The alternator was £49.90 with free postage, ordered Sunday evening and delivered to my local Sainsbury’s/ Argos for collection Tuesday morning. Nigel Quote Link to post Share on other sites
Waldi Posted September 5, 2018 Report Share Posted September 5, 2018 Very good Nigel! Quote Link to post Share on other sites
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