Igol Posted March 30, 2015 Share Posted March 30, 2015 After a new battery and serpentine belt my battery light and rev counter are still flickering and disco dancing, mainly at lower speeds or gears when tourists scared of corners and lanes get in front of me. I've had it hooked up to the multimeter and the figures that come back are as they should be but that's obviously when its not moving when everything is fine anyway. I jury rigged an old voltmeter to the battery this morning and when the dance/flicker was going on the needle on the gauge was solid. My thoughts are now its a bad connection rather than the alternator and I have tried to clean the terminal connection for the rev counter (white wire ??) but its still more black than copper coloured. Anyone have any other thoughts? Quote Link to comment Share on other sites More sharing options...
sierrafery Posted March 30, 2015 Share Posted March 30, 2015 Maybe if we knew what kind of disco it is Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 30, 2015 Share Posted March 30, 2015 I think from past experience before I rewired my Disco that you have a bad connection or broken wire, the rev counter wire gets very hot and the insulation becomes brittle, from then on a break in the wire is an eventual given. On that point, I can NEVER understand why Alternators are made to blow air from the back of the alternator to the front when they are in 99% of their installation instances positioned in front of or near the radiator where they would gain a cooling effect from the vehicle air flow -- ergo it would seem common sense to me to have them blow cooling air from the front to the back but there again I'm only a retired Bsc combustion engineer, what do I know !!!! Quote Link to comment Share on other sites More sharing options...
AMB Posted March 31, 2015 Share Posted March 31, 2015 Assuming that your voltmeter is sensitive enough to note any changes after battery smoothing, I'd tend to agree with the broken/corroded wire diagnosis. To reduce battery smoothing effects on the reading rig your voltmeter directly across the alternator. As to cooling air direction in alternators, I wonder whether it's that clear a decision in practice. You want the most sensitive part of the component receiving best cooling, even if that is at the expense of other items. In an alternator the most sensitive part is the rectifier, usually mounted at the rear of the alternator. Windings etc are rated for much higher temperatures than diodes. Question for a designer should be whether using forced air passing through heated windings provides a lower temperature environment for the rectifier than pulling engine bay air past the diodes first. I don't know the answer, but my first instinct would be to pull air past the rectifier first then look at alternatives. Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 31, 2015 Share Posted March 31, 2015 AMB, totally agree and with our cars its pulling air straight off a red hot turbo -- totally stupid in its concept Quote Link to comment Share on other sites More sharing options...
bear Posted March 31, 2015 Share Posted March 31, 2015 If it's a D2 did you use a genuine belt? Reason I ask is that non-standard ones have a smooth back and can lead to slipping. Griff Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted March 31, 2015 Share Posted March 31, 2015 AMB, totally agree and with our cars its pulling air straight off a red hot turbo -- totally stupid in its concept Unless you duct fresh air to the back of the alternator that seems to make sense, Is it possible to reverse the fan blades? Quote Link to comment Share on other sites More sharing options...
Boydie Posted March 31, 2015 Share Posted March 31, 2015 No, Paul, I've had a good look at the "fan" which comprises of a pressed plate with angled blades, one late model I looked at the blades were formed as part of the plate, the other early unit was a flat plate with spot welded blades, in either case to turn them to cause the cooling air flow to go from the front of the alternator to the rear would be a serious remodelling task and if not done in an engineering shop correctly would possibly affect the balance of the pressed disc "fan", but I'd really like to put the question to Messer's Bosch and Nippon Denso et al as to why they have designed them in this way. It simply doesn't make any logical sense If any auto electrical boffins on the site can explain this please do so .............................. I'm waiting with baited breath Quote Link to comment Share on other sites More sharing options...
sierrafery Posted April 1, 2015 Share Posted April 1, 2015 The alternator cooling setup is generic and well engineered the same for all alternators, the alternator manufacturers dont know(maybe even don't care) where the car's builder will put the alternator and they designed all of them to pull air through the rectifier first, the only way to blow "fresh" air through the rectifier first would be to put the fan behind it which doesnt override the fact that the air there is hot from the turbo, as said if we take into account the engine fan's flow this will blow air against the turbo partially protecting the alternator from it and maybe the air from the engine bay which is sucked through the alternator is colder than the air which would have passed through the hot winding, here's an explanation purely from the alternator benefit's point of view: http://www.cdxetextbook.com/electrical/chargStartLight/altCons/alternatorcoolfan.html Quote Link to comment Share on other sites More sharing options...
Boydie Posted April 1, 2015 Share Posted April 1, 2015 An interesting read but I would like to see a design test carried out with anemometer readings taken regarding air flow volumes and pressure blowing from the front of the vehicle to the rear and if or not it negates the fan forced air flowing through the alternator. I would suspect that alternator fan efficiency in attempting to blow air into the incoming air stream at say 60 mph would be greatly reduced. Any comments ? Quote Link to comment Share on other sites More sharing options...
sierrafery Posted April 1, 2015 Share Posted April 1, 2015 I can't comment on that just reiterate that ALL the alternators are made on the same principle, the fact that LR fitted it so as the air flow can affect it's individual cooling or not is not a problem of the alternator builder..., there are many cars fitted with bosch or denso alternators with transversal engine where the air flow or the vehicle's speed is not so relevant, if what you say it's really an issue IMO it should have been LR's job to make a deflector system or something to provide as cooler air as possible at the back of the alternator though... at least that's bow i see things using only my common sense not science Quote Link to comment Share on other sites More sharing options...
V8 Freak Posted April 1, 2015 Share Posted April 1, 2015 Iain, Thinking about it, all the alternator fans need to do is get the air from inside the alternator to the outside.. It can then be blown back past the alternator in the airflow you mention.... I doubt there is any positive air flow directly into the front of the alternator due to the fan design & pulley. The fan is typically a flat plate at the front and the pulley in front of that blocking a direct route into the alternator..... I suppose the biggest question for me is what is the temperature of the air at the back of the alternator compared to the front.... Is it really pulling cool air in or air that's potentially just cooler than the alternator internals? Quote Link to comment Share on other sites More sharing options...
Sheffield Posted April 3, 2015 Share Posted April 3, 2015 Although we may think it a bit strange to have the air flow in the opposite direction to the general air flow around the engine it seems to work. Generally alternators on LR engines give very little trouble, and only fail because they become worn out, and that after high mileages.. Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted April 3, 2015 Share Posted April 3, 2015 hot air on the regulator (from the windings) would most likely impact voltage stability - the more I think about it I reckon making sure the heat shield is in tact and possibly ducting air to the "input" from a small distance away from the immediate furnace of the exhaust Quote Link to comment Share on other sites More sharing options...
Boydie Posted April 3, 2015 Share Posted April 3, 2015 Yes the heat shield would/could be an advantage I'd guess however the genuine LR part will only fit the early Bosch alternators, not the later Denso units, and Sierra is right, on a transverse engine it wouldn't make any difference which way the air flow went, in face the higher pressure side would be at the end, - not at the fan end so it would work more efficiently but even with out taking any thermocouple readings I think I can safely guarantee that the intake air temperature of my alternator, the intake at the end being less that 2 1/2" from the turbo manifold is a lot higher than the front near the radiator housing. After having, over a 5 year period, two diode packs fail me in above 40 degree C temperatures out in the bush I guess the solution will (for me) to buy an after-market voltage regulator /diode pack and locate it in a cooler remote area and wire it back to the Denso alternator. There simply isn't the room to "duct" cooler air to the rear of the alternator. Anyone done this ? Quote Link to comment Share on other sites More sharing options...
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