Phill S Posted February 17 Share Posted February 17 Been making some headway recently with my V8 transplant into my 1987 110. Not fully sorted yet, but this is how it's looking so far: Ran the engine up yesterday for the first time in a little while, mostly all good but a number of things to get sorted - firstly a dead alternator. No readable markings except the re-manufactured label. When first fired up this time, I had a working rev counter and the battery light extinguished. I'm using a Discovery 1 wiring loom and instrument panel like so: So, on first starting it all looked good - great excitement - RPM settled to a reasonable tickover. Out and checking for fuel spraying about, flames, coolant leaks etc. Back inside a couple of minutes later to do the power steering thing and ensure hydraulics circulating. Imagine my disappointment to find no RPM working and the battery light on... I think it's an AMR4247 - the original VIN was VA738xxx, a 1997 Discovery 1. Here's the connections at the rear: I've used the Disco fuse boxes, the alternator goes first to the engine bay unit, then over the penguin to the bulkhead +ve terminal like so: Today I've been through all of the circuitry for continuity checks and everything is fine. Why would it do this to me? Quote Link to comment Share on other sites More sharing options...
western Posted February 17 Share Posted February 17 ElectroDiesel RCJ on Barncoose Ind Est at Pool can check the alternator & repair it, Quote Link to comment Share on other sites More sharing options...
pat_pending Posted February 17 Share Posted February 17 Worth checking the engine has a GOOD earth back to the battery, stick a jump lead between the Batt neg' and the engine and see if it starts charging. If that's ok and it's been stood standing for a while it may just be the brushes stuck, easy enough to pop the cover off the back of the alternator and check. 1 Quote Link to comment Share on other sites More sharing options...
Peaklander Posted February 17 Share Posted February 17 It sounds as though it was working after engine start and then stopped. It is identical to mine in that view, which is a Hella 120A I think. Quote Link to comment Share on other sites More sharing options...
Paul C Posted February 17 Share Posted February 17 (edited) Factory fit is AMR4247 as you said, 100A, I replaced mine with the 120A one from the p38 RR AMR2938. Mine is Denso. Edited February 17 by Paul C Quote Link to comment Share on other sites More sharing options...
Phill S Posted February 18 Author Share Posted February 18 Morning guys - thanks for the input. 16 hours ago, western said: ElectroDiesel RCJ on Barncoose Ind Est at Pool can check the alternator & repair it, Thanks for that - they'll be going on my people to know about list. Will see if I can fix myself and then check them out if that doesn't work out. I forgot to mention I'm an alternator dummy. 15 hours ago, pat_pending said: Worth checking the engine has a GOOD earth back to the battery, stick a jump lead between the Batt neg' and the engine and see if it starts charging. If that's ok and it's been stood standing for a while it may just be the brushes stuck, easy enough to pop the cover off the back of the alternator and check. Now this sounds promising. I'll do the earth checks and if no joy get it out to check the brushes. There will be more questions in that case. I was a little shocked to find that it's actually 2 years since the alternator did any work - it's been sitting on the shelf all that time, so if sticky brushes are a thing that could be the prime suspect? 15 hours ago, Peaklander said: It sounds as though it was working after engine start and then stopped. That's right - that's why I'd assumed I'd somehow killed it... 13 hours ago, Paul C said: Factory fit is AMR4247 as you said, 100A HIF44's?! Old friends of mine. But I thought you were a 14CUX guy! More questions on that front when I'm past a few other irritants. Like alternators. Remind me to ask you how you did your aircon sometime. Back at the workshop tomorrow, will update after that..... 1 Quote Link to comment Share on other sites More sharing options...
Phill S Posted February 19 Author Share Posted February 19 Jump lead from -ve battery to back of the engine block made no difference so out with the alternator. A label underneath says it's an LRB00283. For future guy having the same problem here's the connectors at the rear: And removing the black plastic cover: reveals the brushes. I can't detect any tendency to stick - all free moving and slide nicely. Is it time to call the menders? 1 Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 19 Share Posted February 19 Did you by any chance jump start it? Quote Link to comment Share on other sites More sharing options...
Phill S Posted February 19 Author Share Posted February 19 No, just a regular start on the battery... Quote Link to comment Share on other sites More sharing options...
Phill S Posted February 20 Author Share Posted February 20 Ok - this video is at about my level. A different alternator to what we have, but I assume the principles are the same. You can skip along until 11:05 where the off-car tests start. I got 2.8 Ohms at the slip rings - the uppermost brush pushed back and the tip of a cable tie pushed in to break the circuit. It was all over the place before that. I'm not cleat what he's doing after that though.... I don't understand what the 421 is? Anybody? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 21 Share Posted February 21 16 hours ago, Phill S said: I don't understand what the 421 is? Anybody? Looking at the meter it's in diode test mode so 421 is probably 421mV reverse voltage from battery terminal to casing as the leads are reversed. Quote Link to comment Share on other sites More sharing options...
bishbosh Posted February 21 Share Posted February 21 Disclaimer - I am definitely not an auto electrician.... ......but on my multimeter that is the continuity test position so would suggest there is a degree of resistance in that circuit? Perhaps? Maybeeeee? (see disclaimer!) Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 21 Share Posted February 21 2 hours ago, bishbosh said: ......but on my multimeter that is the continuity test position so would suggest there is a degree of resistance in that circuit? Perhaps? Maybeeeee? (see disclaimer!) It's continuity and diode test, *usually* in continuity mode there's a little icon in the top of the screen but it could equally be the case that it would show a little diode icon in diode mode, or possibly nothing either way and the display could be reading ohms OR millivolts... Quote Link to comment Share on other sites More sharing options...
Phill S Posted February 21 Author Share Posted February 21 Ahaaa - ok - I think. Got some more digging to do on this. Back with progress updates in a couple of days... Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 22 Share Posted February 22 There's a pretty good page or two in the Series 3 green bible on testing an alternator, and it hasn't really changed since. Quote Link to comment Share on other sites More sharing options...
Phill S Posted February 22 Author Share Posted February 22 Ok - thanks. Would never have thought to look there... Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 22 Share Posted February 22 Back when alternators were new & exotic and also expensive enough to warrant repairing! Quote Link to comment Share on other sites More sharing options...
Phill S Posted March 4 Author Share Posted March 4 Finally managed to get this sorted out over the weekend. Armed with the information that the weird symbol on my every expense spared multimeter (like the symbol on the one in the video pic above) means diode test, I checked out the 6 contacts and they all did what they were supposed to do. The vehicle was previously 24v, now re-wired for 12v and had 2 batteries which individually aren't man enough to start the engine, and to date I've been using a bigger battery which is on it's last legs, but perfectly capable of starting the engine when fully charged. I had wondered if the alternator might be unhappy charging a dodgy battery, but having said that it was charging ok and the Disco 1 rev counter was working as described in my opening account of the problem. Anyhow, being basically a tight wad I decide to connect up the two small batteries in parallel as a get me going until the super duper split charge system gets put in. And so I can get an MoT. This meant going for a different chassis earth point as a result of the odds and ends of cables I had to hand. Like you do. Ok, so now let's put it all back together and see if anything has changed. like maybe it'll work now. And it did. Everything working fine, battery light gone out and rev counter working. Cheapo voltage indicator showing the right sort of things happening - 14.2v. Now, I'm pretty sure the earth was fine before the battery config change, and the jump lead to back of the engine would/should have sorted that if so (excellent tip!). So am I just rationalising in thinking it must have been the alternator brushes? Alternator sits on the shelf for two years, works for a short time and then doesn't. I guess it would only take one of the brushes to have been stuck... Quote Link to comment Share on other sites More sharing options...
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