Mk3iain Posted January 8, 2012 Share Posted January 8, 2012 Hi All I have a very dim generator light, the system uses a No10 Mk2 generator and a No9 Mk3 panel. I have a spare No9 Mk4 panel, are these interchangeable? The original problem happened when moving the cable that connects the generator and panel, afterwards the generator light would not work. I changed an internal diode but now the light is very dim. It would help if I could fit the No9 Mk4 if only to test! Cheers Iain Quote Link to comment Share on other sites More sharing options...
airportable Posted January 8, 2012 Share Posted January 8, 2012 Loads of first class info. here. Sorry dont know how to post link but I just typed 'All charged up' in search box, pressed enter, scroll down and all the posts are there, 1,2,3. (Good luck with sorting, have had same probs. myself) Quote Link to comment Share on other sites More sharing options...
Mk3iain Posted January 8, 2012 Author Share Posted January 8, 2012 Loads of first class info. here. Sorry dont know how to post link but I just typed 'All charged up' in search box, pressed enter, scroll down and all the posts are there, 1,2,3. (Good luck with sorting, have had same probs. myself) Thanks for the tip. I have just found the mention in part one of the interchangeability of the Mk4 in the Mk3 installation, saying that it will "for the time being work normally" . The article goes on to mention the differences in the auxiliary diodes and it seems there may be a possibility of overloading the aux diodes in the generator,....... I think!:??? HELP!....Clive? Quote Link to comment Share on other sites More sharing options...
fv1609 Posted January 8, 2012 Share Posted January 8, 2012 In a POWER EMER it indicates that it is acceptable to use use a Mk 4 Panel in what was originally a set up for a Mk 3 Panel ie having the Mk 2 Generator. But the other way round the the charge light won't work, but it will still charge. As it had the authority of an EMER, I accepted it at face value when I wrote the first ACU article. When I wrote ACU4 I delved further into the history of the auxiliary diodes in the Mk 3 Generator. You can see in ACU4 that three different types of diode were used, each time increasing in their power handling so much so that modern alternators handling these loads have auxiliary diodes of similar properties to the main diodes. The problem is that the auxiliary supply in the Mk 4 Panel has much higher demands as it feeds into the field regulation, in the earlier panels it just had to power the BCK relay. So we have these various diode failures in the generator designed to give adequate auxiliary output yet the earlier types were prone to fail. I feel that if you use a Mk 2 generator with even weedier diodes they are likely to fail sooner or later. Although it surprises me this has never been alluded to in an EMER. But for a short substitution test I'm sure you would get away with it. There may well be people who will come on & say they use the "wrong" combination for years & it would be interesting to hear such reports. But it's not a set up I would want to run on my vehicle. You said you "changed an internal diode" where was that? Quote Link to comment Share on other sites More sharing options...
Mk3iain Posted January 8, 2012 Author Share Posted January 8, 2012 Many thanks Clive! I changed diode D4 as the charge light was not working at all and when I removed the diode and tested it, it was (if I remember correctly) OC both ways. Now the light is dim but goes out when it should!...... Iain Quote Link to comment Share on other sites More sharing options...
fv1609 Posted January 8, 2012 Share Posted January 8, 2012 Iain well done, D4 is an awkward one to get at & well done diagnosing it. Neglecting the dimness of the light, is it actually charging ok? Quote Link to comment Share on other sites More sharing options...
Mk3iain Posted January 9, 2012 Author Share Posted January 9, 2012 Iain well done, D4 is an awkward one to get at & well done diagnosing it. Neglecting the dimness of the light, is it actually charging ok? I can measure 28v at the batteries at around 700rpm so it seems OK. I will give the Mk4 panel a go and see about getting the Mk3 repaired (if it is that, or the generator if that's the problem) as I would rather fix them than chuck them out. Iain Quote Link to comment Share on other sites More sharing options...
fv1609 Posted January 9, 2012 Share Posted January 9, 2012 I would rather fix them than chuck them out.Iain Good man that's the spirit! Quote Link to comment Share on other sites More sharing options...
Iain Crosbie Posted January 9, 2012 Share Posted January 9, 2012 Just a thought... I suppose it's the correct bulb, and the bulb holder has good connections? Quote Link to comment Share on other sites More sharing options...
Mk3iain Posted January 10, 2012 Author Share Posted January 10, 2012 Hi Iain I must admit I had to double check but I do remember the problem starting after moving cables, so it was OK before. I have just slaved in a Mk4 panel and the charge lamp works as it should (goes out between 4-500rpm) and is of normal brightness, sadly the voltage at the batteries is a steady 25v showing no charge at any revs! Hmm.... but it at least shows original the problem is with the panel. Iain Quote Link to comment Share on other sites More sharing options...
fv1609 Posted January 10, 2012 Share Posted January 10, 2012 Ian ok so the Mk 4 panel is NBG, but at least it shows generator output to SK1 Pin A is ok & the lead from PL2 Pin E is ok for the charge light to be working normal. Worth investigating further as you must be getting some output to drive the bulb out. As Pin A is connected to X you are getting output from the main winding & diodes. Worth putting a meter on X & seeing if that goes up with revs, it must be to some degree to drive the light off. Anyway going back to the Mk 3 panel, I would measure the resistance between A & E. One way should read 250 ohms the other way 38 ohms or so. But use an analogue meter not a digital. Digital will not forward bias the diode into conduction adequately like an analogue meter. I know some digitals have a diode test facility that does bias the diode, but here you have a resistor in parallel & it may give a misleading result when you are in effect measuring the voltage drop across the diode when it is conducting. Before you dismantle it to get to the diode again. You could disconnect A or E then jump leads to A & E with a replacement diode & resistor, then see what the charge light does. Quote Link to comment Share on other sites More sharing options...
Mk3iain Posted January 10, 2012 Author Share Posted January 10, 2012 Ian ok so the Mk 4 panel is NBG, but at least it shows generator output to SK1 Pin A is ok & the lead from PL2 Pin E is ok for the charge light to be working normal. Worth investigating further as you must be getting some output to drive the bulb out. As Pin A is connected to X you are getting output from the main winding & diodes. Worth putting a meter on X & seeing if that goes up with revs, it must be to some degree to drive the light off. Anyway going back to the Mk 3 panel, I would measure the resistance between A & E. One way should read 250 ohms the other way 38 ohms or so. But use an analogue meter not a digital. Digital will not forward bias the diode into conduction adequately like an analogue meter. I know some digitals have a diode test facility that does bias the diode, but here you have a resistor in parallel & it may give a misleading result when you are in effect measuring the voltage drop across the diode when it is conducting. Before you dismantle it to get to the diode again. You could disconnect A or E then jump leads to A & E with a replacement diode & resistor, then see what the charge light does. Thanks Clive, I'll have a go at the weekend. I suppose it is about time I got an AVO (its as good an excuse as any), its been a while but I feel I could still handle one:whistle: Iain Quote Link to comment Share on other sites More sharing options...
fv1609 Posted January 10, 2012 Share Posted January 10, 2012 I suppose it is about time I got an AVO (its as good an excuse as any), its been a while but I feel I could still handle one:whistle: Iain I think that would be a good move. There are some nice looking Avo 8 meters on e bay. I would go for a Mk 4, 5 or 6. I find the scale on Avo 7 very difficult to read & the ranges are not so good. It is worth paying more for one in a leather case (that could cost you £20 separately) & complete with leads & clips (again that could cost you another £20 separately) also try to get one with a new 15v battery fitted Get an undertaking from the seller that it is fully working on all ranges. If it is untested then you don't know if it is untested or tested but not working. Perhaps try to buy from a dealer who has several eg selling a batch withdrawn from a college where they have gone digital. There are the usual crop of multimeters sold as Avometers, when they most certainly are not Avometers. I bought a nice Avo 8 last year but both batteries were corroding and it was inaccurate on some voltage ranges. So check it out as soon as you get it, I'm glad I checked mine. The dealer doesn't accept returns, but he accepted this one. It was replaced by a nice one & he paid my return postage. Many EMERs will give readings measured on Avo 7, 8 or 12, so it is nice to measure the resistance with the same meter quoted when it comes diode testing as it will vary with the meter. The Avo 12 is rare but nice, designed for automotive use with a current range of 36A without a shunt. Low ohms per volt so some weedy micro current stray voltage won't budge the needle. Not like a digital meter which will detect it, in fact even an expensive military Fluke I have displays reading of voltage or resistance when you are not even measuring anything. I can't be done with nonsense like that! In fact last year was a good avo year, I bought an Avo 8 and two Avos 12. There are no Avos 12 on e bay at the moment. But if you search for "Avo 12" you'll get lots of hits like this http://www.ebay.co.uk/itm/AVO12-New-Sexy-Chic-Women-Sleeveless-Backless-Party-Cocktail-Dress-Ribbon-Belt-/150701625254?pt=UK_Women_s_Dresses&hash=item2316844fa6 Quote Link to comment Share on other sites More sharing options...
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