DaveSIIA Posted December 11, 2008 Share Posted December 11, 2008 Could I suggest that you limit testing to just one battery installed (known good). There are four main voltage readings to be taken with the engine running and the battery in circuit - Alternator +ve output to alternator case Battery +ve to battery -ve Alternator +ve output to battery +ve Alternator case to battery -ve Start the engine and let it run at a fast idle for ~1 minute to put some charge back in to the battery before taking the readings. Make sure the leads to the meter contact directly on the battery / alternator posts rather than wiring terminals. Repeat the test with every electrical appliance switched on (lights, heated rear window, fan, etc). Also measure battery -ve to a good earth on the body or chassis. The results will show any poor connections in the circuit and that the alternator can deliver the goods under heavy load. If all is well then start chasing residual current drains with an ammeter. BTW: Voltage dropping as revs increase could be a sign of a faulty regulator or poor brush contact with the slip rings (inside the alternator). Quote Link to comment Share on other sites More sharing options...
Paul64 Posted December 11, 2008 Author Share Posted December 11, 2008 Thanks to both Davids! I will try your suggested tests and report back. It may take a couple of days as the builders are in again, and I will be the manual cement mixer. Just a couple of other points to add. The second alternator is 2nd hand on loan whilst Marcus is away in Iraq. His 90 has been out of action for months, so the efficiency of it is unknown. All I can say is that on the original alternator with increased revs the V did climb. Also when I was cleaning up the separate battery earths, I noted that one lead went to both chasis and gearbox and the other only went to gearbox. Is that OK? Thanks again for all the advice. It really has been a steep learning curve! Cheers, Paul Quote Link to comment Share on other sites More sharing options...
western Posted December 11, 2008 Share Posted December 11, 2008 earth leads -- from battery to gearbox/transfer box joint bolt, & from alternator/power steering pump bracket to the chassis part of the engine mounting. both battery earth leads can be joined & then 1 to gearbox location. Quote Link to comment Share on other sites More sharing options...
Paul64 Posted December 12, 2008 Author Share Posted December 12, 2008 earth leads -- from battery to gearbox/transfer box joint bolt, & from alternator/power steering pump bracket to the chassis part of the engine mounting. both battery earth leads can be joined & then 1 to gearbox location. Thanks Ralph. Both terminate at the gearbox/transfer box, so that sounds like it is in order. Quote Link to comment Share on other sites More sharing options...
Paul64 Posted December 22, 2009 Author Share Posted December 22, 2009 Hi, Incredibly, I'm still not on top of this problem! The most recent changes to the system are two new 65 amp batteries and an x-eng split charger. However, the following happens when testing the voltage. Multimeter connected to either battery on idle 13.6V. When I then increase the revs the volts drop to about 13.2V, when they should be increasing? When the engine is turned off, the main battery V slowly drops to and settles around 12.2V. This only has the main power feed and starter connected. The second batt settles at about 12.6V with everything else connected including the winch. Not have much knowledge in this area, so am I missing something simple? Cheers, Paul Quote Link to comment Share on other sites More sharing options...
SiWhite Posted December 22, 2009 Share Posted December 22, 2009 I have experienced charging problems in the past. Mine we solved by changing the regulator pack on the back of my alternator, and by running an auxillary earth cable from the alternator mounting bracket directly to the battery negative post. This cable will supplement the existing earth, and provide a guaranteed earth even if the underseat chassis to battery connection gets a bit crusty. Quote Link to comment Share on other sites More sharing options...
Aragorn Posted December 22, 2009 Share Posted December 22, 2009 Theres something not right with the battery thats dropping to 12.2v. 12.2v indicates the battery is in a discharged state. If your only getting 13.2v out of the alternator though, it will not be charging properly, which might explain it. The fact the voltage from the alternator drops is also not right. Someone suggested it might be poor brush contacts... Since the alternator is a spare from an unknown vehicle, i'd perhaps look at getting a replacement that you know works, or a new unit. Quote Link to comment Share on other sites More sharing options...
Paul64 Posted December 22, 2009 Author Share Posted December 22, 2009 I have experienced charging problems in the past. Mine we solved by changing the regulator pack on the back of my alternator, and by running an auxillary earth cable from the alternator mounting bracket directly to the battery negative post. This cable will supplement the existing earth, and provide a guaranteed earth even if the underseat chassis to battery connection gets a bit crusty. Thanks for the tips Si. The earthing issue comes up regularly in replies, so I am going to look at that next when the weather improves. I also had a long telephone chat this morning with Simon at X-Eng. He gave me some great advice too. He's a top drawer chap who obviously understands the meaning of after sales service! My problems have nothing to do with his split charger, and all I wanted was some advice on options without damaging it. He gave me loads of good tips taking half an hour of his time which in my book deserves acknowledgement! Cheers, Paul Quote Link to comment Share on other sites More sharing options...
errol209 Posted December 22, 2009 Share Posted December 22, 2009 Simon at X-Eng. He's SimonR on this very forum. Quote Link to comment Share on other sites More sharing options...
Paul64 Posted February 7, 2010 Author Share Posted February 7, 2010 I heard an interesting theory the other day about my alternator and wanted to know if the following makes any sense? (Apologies if this has already been discussed!) With a multimeter attached to the battery the number of volts drops when I rev the engine, when I thought they should be going up? I was told that this could be due the alternator having the wrong size pulley wheel? I know the alternator is not original, and I don't know of it's origin. Does this sound feasible? Thanks in advance, Paul Quote Link to comment Share on other sites More sharing options...
western Posted February 7, 2010 Share Posted February 7, 2010 Possible, IIRC there are 2 pulleys that will fit a 46mm & a 61mm http://www.brit-car.co.uk/product.php?xProd=91279&xSec=5497 your 200tdi alternator should be a 65amp with the 61mm diameter pulley Quote Link to comment Share on other sites More sharing options...
Paul64 Posted February 7, 2010 Author Share Posted February 7, 2010 Possible, IIRC there are 2 pulleys that will fit a 46mm & a 61mm http://www.brit-car.co.uk/product.php?xProd=91279&xSec=5497 your 200tdi alternator should be a 65amp with the 61mm diameter pulley Thanks Ralph, Just been outside to measure it and it is 61mm. At least that is one more thing I can rule out. I have already checked the earths, so I think it is going to have to be a new alternator as I have already bought new batts. Just been looking at that Britcar pulley, 62.65 quid inc VAT! Wow, that's a bit pricey when you can pick up a new alt for 80? Cheers, Paul Quote Link to comment Share on other sites More sharing options...
western Posted February 7, 2010 Share Posted February 7, 2010 sounds like a poor rectifier in the alternator, hope you have a good tame auto electrician out there. Quote Link to comment Share on other sites More sharing options...
Paul64 Posted February 7, 2010 Author Share Posted February 7, 2010 sounds like a poor rectifier in the alternator, hope you have a good tame auto electrician out there. I will be driving to the UK in March, so I am going to sort it out then. I have approached a few UK companies about alternators, but most loose interest when I mention I'm based outside the UK. I bought this trickle charger from Germany, so I can top up every now and again. The cold is the biggest problem, and each night I look up at the sky to see if there is cloud cover. This is usually the best indicator whether the LR will start in the morning! Cloudless night, Paul in plight! Thanks again, Paul Quote Link to comment Share on other sites More sharing options...
errol209 Posted February 7, 2010 Share Posted February 7, 2010 I heard an interesting theory the other day about my alternator and wanted to know if the following makes any sense? (Apologies if this has already been discussed!) With a multimeter attached to the battery the number of volts drops when I rev the engine, when I thought they should be going up? I was told that this could be due the alternator having the wrong size pulley wheel? I know the alternator is not original, and I don't know of it's origin. Does this sound feasible? No, not normal. Feasible, but not right at all. The alternator output should be at or just under the battery voltage at idle after you start the engine, and rise to a bit above when you rev it, and it should then stay a tiny bit above whilst the engine is running. If the voltage drops as you rev, this means it is putting a load on the battery and not charging it (the alternator voltage has to be a little higher than the batttery voltage to overcome the internal resistance of the battery and get charge into it), which is why your battery isn't doing very well. I second Ralph on his diagnosis of the fault (for the fault, not Ralph's diagnosis!) Quote Link to comment Share on other sites More sharing options...
Paul64 Posted February 7, 2010 Author Share Posted February 7, 2010 No, not normal. Feasible, but not right at all. The alternator output should be at or just under the battery voltage at idle after you start the engine, and rise to a bit above when you rev it, and it should then stay a tiny bit above whilst the engine is running. If the voltage drops as you rev, this means it is putting a load on the battery and not charging it (the alternator voltage has to be a little higher than the batttery voltage to overcome the internal resistance of the battery and get charge into it), which is why your battery isn't doing very well. I second Ralph on his diagnosis of the fault (for the fault, not Ralph's diagnosis!) Thanks. I remember seeing the rectifier split on my last alternator when that stopped working. A local auto electrician found that one of the diodes was not working, removed it and soldered in another from a Dacia! It didn't work very long which is why I changed it. The alt I have now was also 2nd obtained from another ex-pat, but he didn't know how old it was. It did get me out of a fix though, so looks like I need to invest in a good one. Would you say Paddocks would be the best bet? Cheers, Paul Quote Link to comment Share on other sites More sharing options...
western Posted February 7, 2010 Share Posted February 7, 2010 as your coming back to UK for a bit, one from a Lucas vehicle electrical agent might be better at least they should know what they are doing, know their products. Quote Link to comment Share on other sites More sharing options...
Paul64 Posted February 7, 2010 Author Share Posted February 7, 2010 as your coming back to UK for a bit, one from a Lucas vehicle electrical agent might be better at least they should know what they are doing, know their products. Thanks Ralph Quote Link to comment Share on other sites More sharing options...
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