tuko Posted January 6, 2011 Share Posted January 6, 2011 On my way home from work last night the lights in my hybrid began pulsating, not just the headlights but every single lamp that was lite plusated. Today checking for faults I eliminated the alt., she's producing a steady 14.3-14.4V. The ground connections (2 in total) were tight. Checking that battery nothing the voltage was stable with the motor running and off. I'm a bit baffled, what could be causing this pulsation? The only thing that I can think of right now is possibly the voltage stabiliser is at fault. Any other suggestions? Cheers, Todd. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted January 6, 2011 Share Posted January 6, 2011 Not sure what you mean by voltage stabiliser. The one in the instrument panel only regulates the fuel and temperature gauge. The rest of the electrics are regulated by the regulator in the alternator, unless you have an alternator with an external regulator? How fast was the pulsating? did the lights just dim or go out completely? When you tested the alternator output did you have the lights on? Did you use a digital or analogue meter to check the alternator? Did the pulsating occur at all engine speeds? Diesel or Petrol? If petrol was the engine misfiring at all? What colour is it? Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted January 6, 2011 Share Posted January 6, 2011 I agree, my first thought is alternator. The crucial check might be to set the multimeter on AC rather than DC when measuring the output. By all means test while the fault is not apparent, but don't take the results as definitive. Be prepared to repeat the test the next time you become a Disco Diva :-) The fault may be temperature sensitive, at the moment, so only apparent when the alternator becomes warm. I suggest you put your spare, and the appropriate spanners, in a box in the boot, load bay, passenger footwell, whatever. Good Luck. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted January 6, 2011 Share Posted January 6, 2011 The crucial check might be to set the multimeter on AC rather than DC when measuring the output. That's interesting, what's the theorey behind that? Quote Link to comment Share on other sites More sharing options...
tuko Posted January 6, 2011 Author Share Posted January 6, 2011 Not sure what you mean by voltage stabiliser. The one in the instrument panel only regulates the fuel and temperature gauge. The rest of the electrics are regulated by the regulator in the alternator, unless you have an alternator with an external regulator? How fast was the pulsating? did the lights just dim or go out completely? When you tested the alternator output did you have the lights on? Did you use a digital or analogue meter to check the alternator? Did the pulsating occur at all engine speeds? Diesel or Petrol? If petrol was the engine misfiring at all? What colour is it? Man the questions The first part of your questions, I was grasping at straws and thats why I wrote voltage stabiliser and yes your correct, the one on the back of the speedo for the gauges. The lights are pulsating at a regular rate at idle, didn't check at fast idle. But no, the lights didn't go out, just pulsating. Yes I tested the alt. with the lights on with a digital meter. engine, 300Di runs like it should with no lumpy idle. Oh, the color is messa brown. I have an extra alt from the disco, so maybe I'll try that for fit and see how the engine reacts. Todd. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted January 6, 2011 Share Posted January 6, 2011 You'd be better with a cheap analogue meter, you could then maybe see the needle puslating. If the rate varies with engine speed and is regular I'd definitely suspect the alternator. Quote Link to comment Share on other sites More sharing options...
M&S Posted January 6, 2011 Share Posted January 6, 2011 Had the same problem with my TD5 and it was the alternator. That was giving steady voltage as well... Actually I think my totally flat battery had something to do with it as well. Have you checked your battery voltage (after it's been sat for a while, maybe in the morning before starting?)/ Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted January 6, 2011 Share Posted January 6, 2011 The crucial check might be to set the multimeter on AC rather than DC when measuring the output. That's interesting, what's the theory behind that? An alternator produces 3 phase AC, which is then full wave rectified to DC. If any of the rectification circuitry starts to fail it's possible for AC to be present 'behind' the DC. By putting the meter to AC it tends to block the DC component and just show the AC. There can be variations depending on the design of the meter. On some of them you might have to reverse the leads to see the AC, but that's hardly an onerous check. Oh, you might have to adjust the scale to get a meaningful reading. Regarding your other point about an analogue meter showing the AC by a pulsing needle I'll accept that it can, but if the signal strength is low the needle might just 'tremble', and a novice might miss that :-) HTH Quote Link to comment Share on other sites More sharing options...
rtbarton Posted January 6, 2011 Share Posted January 6, 2011 By putting the meter to AC it tends to block the DC component Depends on the meter, it will only block the DC component if there is a capacitor on the input. The meters I've used simply switch a bridge rectifier into the circuit and maybe add a circuit to give a true RMS reading. Regarding your other point about an analogue meter showing the AC by a pulsing needle I'll accept that it can, but if the signal strength is low the needle might just 'tremble', and a novice might miss that :-) If the variation is noticeable in the lights then it should easily be seen on a meter needle. Quote Link to comment Share on other sites More sharing options...
Snagger Posted January 7, 2011 Share Posted January 7, 2011 It's definitely the alternator or its wiring connection to the starter motor solenoid where it joins the main loom - the battery has lower voltage, so when the engine is running, any battery fault will be masked by the alternator output. You have checked that the alternator is being driven properly, haven't you? Make sure the belt tensioner is working properly, that the belt is not worn or stretched (the two raised lines on the tensioner hub should be separated - if they're in line, the belt has had it) and that the pulley is tight on the alternator shaft. Quote Link to comment Share on other sites More sharing options...
tuko Posted January 7, 2011 Author Share Posted January 7, 2011 Thanks Nick I'll check the start motor solenoid later today. The water pump and serpentine belt are both new two weeks ago, but I will look at the pulley on the alt to. Cheers, Todd. Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted January 7, 2011 Share Posted January 7, 2011 By putting the meter to AC it tends to block the DC component Depends on the meter, it will only block the DC component if there is a capacitor on the input. The meters I've used simply switch a bridge rectifier into the circuit and maybe add a circuit to give a true RMS reading. The fact that the appropriate test gear isn't available doesn't make the test invalid. In this case testing for AC is a valid test, however it is achieved. It could be tested by keeping the meter on DC and putting a capacitor in series with one of the leads. A lot of people have a distributor points spark quench 'condenser' available. Again, the meter leads may need reversing to pick up an inverse pulse. Nowadays I'd expect a professional to have a scope available. That said, I only work on my cars as a hobby, so I haven't bothered investing. Regarding your other point about an analogue meter showing the AC by a pulsing needle I'll accept that it can, but if the signal strength is low the needle might just 'tremble', and a novice might miss that :-) If the variation is noticeable in the lights then it should easily be seen on a meter needle. Maybe, maybe not, I'll be interested to see what Todd reports. Long distance analysis always has an air of uncertainty about it, because the poster may (inadvertently) miss out some vital clue, or when testing may miss the significance of a sign which means a lot to someone more experienced in the field. Shrug, wait and see :-) Friday morning is snowy in Sheffield I hear; we recently had a call for someone in 4x4Response to take blood from Sheffield to Manchester. Quote Link to comment Share on other sites More sharing options...
rtbarton Posted January 7, 2011 Share Posted January 7, 2011 Yup, couple of inches in my street, just when I'm waiting for a delivery! Quote Link to comment Share on other sites More sharing options...
Snagger Posted January 8, 2011 Share Posted January 8, 2011 Thanks Nick I'll check the start motor solenoid later today. The water pump and serpentine belt are both new two weeks ago, but I will look at the pulley on the alt to. Cheers, Todd. Just to be clear, it's not the solenoid itself that you need to check, just the connection to it - the alternator output connects to the LR's fuse box main power feed (thick brown wire) on that terminal stud, and if it's loose or dirty, you may have a poor contact between the alternator and loom. Quote Link to comment Share on other sites More sharing options...
tuko Posted January 9, 2011 Author Share Posted January 9, 2011 Sorry for the delayed reply guys, busy with guests this weekend but once they left this afternoon I had a good prod around the alt and can confirm what you've all been saying, it was the alt at fault. The original from that motor was AMR4249 (64Amps) that I replaced during the engine conversion with AMR5425E (100Amps). Kinda disappointing to see that the LR exchange unit died so quickly. But with that said, the original alt is back on the motor for the time being and yes it works fine. I want to go back to an 100Amp alt, checking at mailorder4x4's site they only have AMR4248 as an 100Amp alt for the 300Tdi motor for the Disco only. Searching here on the forum this post by cipx2, on Mar 9 2009 was interesting: AMR5425 is for 97-98 Discovery. For 94-96 Discos the part# is AMR4248.YLE10113 is more like a one size fits all but actually it fits nothing It can be fixed to fit though. Ok, my motor came from a 1997 Defender and I was using the AMR5425 alt without any mounting issues. I'm now wondering if I can use AMR4248 on the 1997 300Tdi? It is an 100Amp alt that I want but I've not found any pictures or info that would suggest that it differs or the same as the others. Is there anybody that can confirm that I could use AMR4248 on a 1997 300Tdi or suggest something other? Cheers, Todd. Quote Link to comment Share on other sites More sharing options...
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