NikolaiV Posted February 1, 2008 Share Posted February 1, 2008 Hi there from NZ. I have a 1978 2dr Rangie, whose speedo has just died in a clicking frenzy. I have it on good advice that its the angle drive (they all do that sir...). I`ve checked the price for a new one - $NZD 232, about GBP91... which is a bit expensive for my tastes. My question is this, I can obtain a complete instrument cluster from a later 4 door rangie (with tacho etc) - will the speedo drive be geared the same, and will the gauges work? The trusty haynes manual shows all the wire colours as being identical between the two so i might be lucky. Also i`m sure the senders look the same (and in all likelyhood are the same) This would let me have a tidy factory tacho added on, as i dont want to have some boy-racer looking tach on my dash (so everyone can see how high the beast revs...), as well as getting me a warrent of fitness (like your MOT) I look forward to your sage advice Quote Link to comment Share on other sites More sharing options...
SteveRK Posted February 1, 2008 Share Posted February 1, 2008 Dependant on the year it will either be a cable driven speedo or later electronic wire fed speedo. The change point was with the introduction of the flapper fuel injection engine so if you can find out what engine the speedo came from then you are in with a chance. The rev counters are driven from a feed off the ignition coil '-' terminal. There is a resistor fitted in series between the '-' LT connection and rev counter to reduce the voltage at the rev counter (and ECU for fuel injected engines) of 6800 Ohms (6.8K) as there will be a lot of high voltage spikes on the coil LT connections. Quote Link to comment Share on other sites More sharing options...
landybehr Posted February 3, 2008 Share Posted February 3, 2008 Hi, read here: http://forums.lr4x4.com/index.php?showtopic=19341 in that thread, some questions will be answered. BTW: are you sure, the rev-counter is fed by the ignition coil ? On my 3.9 (which already has one RoadSpeedTransducer to serve the ECU and the elect. speedo as weel on post 1990 models) I am quite sure that the rev signal comes from the alternator ("W"). Quote Link to comment Share on other sites More sharing options...
steve_d Posted February 4, 2008 Share Posted February 4, 2008 I had that speedo right angle gearbox fail on my RRC. I took it apart and shimmed out the free play and it has been working for years. Steve Quote Link to comment Share on other sites More sharing options...
V8RRC Posted February 4, 2008 Share Posted February 4, 2008 BTW: are you sure, the rev-counter is fed by the ignition coil ? On my 3.9 (which already has one RoadSpeedTransducer to serve the ECU and the elect. speedo as weel on post 1990 models) I am quite sure that the rev signal comes from the alternator ("W"). My 3.5 EFi is of 1989 vintage & my rev counter is also connected to the alternator as stated above! Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted February 4, 2008 Share Posted February 4, 2008 BTW: are you sure, the rev-counter is fed by the ignition coil ? On my 3.9 (which already has one RoadSpeedTransducer to serve the ECU and the elect. speedo as weel on post 1990 models) I am quite sure that the rev signal comes from the alternator ("W"). The tacho on my '93 3.9 was driven from the alternator - however the engine ECU took it's timing signal from the ignition coil. One gotcha is that the alternators fitted to these vehicles output a voltage (+5V, I think) with a slight wave form in it which was the tacho signal. Modern alternators output a squarewave pulse tacho signal which is not recognised by the tacho (or the air suspension ECU if you have EAS - it uses the tacho signal to determine whether the engine is running). Quote Link to comment Share on other sites More sharing options...
landybehr Posted February 5, 2008 Share Posted February 5, 2008 Hi Geoff, that waveform thing puzzles me. I always thought that the tacho-output of alternators is just a internal-length-of-wire that connects one of the 3 windings to a plug at the rear of the alternator. Whenever the anchor passes that winding a signal of 12volt is generated. Could be that some kind of rectifier or other stuff I have no knowledge about works to modify the signal on new alternators. The "young" Bosch alternator that I have is carefully "sealed" with covers and things and I didn´t dare to take it apart. With the old vintage Lucas alternators I managed to solder in a wire that looked outsides and could be connected to an aftermarket tacho on my 200TDI-88"SIII. The Bosch unit in my RRC doesn´t work the tacho but I blamed it for being an ebay purchase (seller said it was taken off from a new car) and that this was the real reason for it being sold on ebay. The article on rangerovers.net that guided me through swapping to a Bosch unit did not mention any problems with the tacho gauge. And the Bosch alternators recommended are used in cars common only 10years ago. http://www.rangerovers.net/rrupgrades/elec...alternator.html Quote Link to comment Share on other sites More sharing options...
landybehr Posted February 5, 2008 Share Posted February 5, 2008 Hi Geoff,that waveform thing puzzles me. I always thought that the tacho-output of alternators is just a internal-length-of-wire that connects one of the 3 windings to a plug at the rear of the alternator. Whenever the anchor passes that winding a signal of 12volt is generated. Could be that some kind of rectifier or other stuff I have no knowledge about works to modify the signal on new alternators. The "young" Bosch alternator that I have is carefully "sealed" with covers and things and I didn´t dare to take it apart. With the old vintage Lucas alternators I managed to solder in a wire that looked outsides and could be connected to an aftermarket tacho on my 200TDI-88"SIII. The Bosch unit in my RRC doesn´t work the tacho but I blamed it for being an ebay purchase (seller said it was taken off from a new car) and that this was the real reason for it being sold on ebay. The article on rangerovers.net that guided me through swapping to a Bosch unit did not mention any problems with the tacho gauge. And the Bosch alternators recommended are used in cars common only 10years ago. http://www.rangerovers.net/rrupgrades/elec...alternator.html How likely is it the tacho want´s a 5Volt input ? Could be good news for me because there is still a tiny bit of hope gleaming in me that there´s a way to connect the Megasquirt Tach-output to the RRC tacho (the reading would be spot on). Unfortunately this seems to be nothing anybody managed or bothered to do. And I nowhere have enough knowledge about these things to be the first. Quote Link to comment Share on other sites More sharing options...
SteveRK Posted February 5, 2008 Share Posted February 5, 2008 Hi,read here: http://forums.lr4x4.com/index.php?showtopic=19341 in that thread, some questions will be answered. BTW: are you sure, the rev-counter is fed by the ignition coil ? On my 3.9 (which already has one RoadSpeedTransducer to serve the ECU and the elect. speedo as weel on post 1990 models) I am quite sure that the rev signal comes from the alternator ("W"). You are quite right Landybehr - the rev counter is driven off the alternator - my mistake. Sounds like this conversion will get complicated if the existing alternator doesnt provide an RPM signal Quote Link to comment Share on other sites More sharing options...
landybehr Posted February 5, 2008 Share Posted February 5, 2008 No, don´t think the tacho is an issue. All the RRC have the tach-input from the alternator. The elect.troubleshooting manual does not mention anything special. Just that the alt. supplies the frequency of voltage spikes/waves - which raises with rpm´s. I am quite sure that my alternator is the culprit in my case. I will try the exchange it with another unit. The 120Amps unit I have in is unnecessarily strong anyway - sometime more than the standard belt can handle. A 90Amps alternator should do perfectly. Quote Link to comment Share on other sites More sharing options...
geoffbeaumont Posted February 6, 2008 Share Posted February 6, 2008 I'm pretty certain that Megasquirt outputs a pulse type tach signal which isn't any use to you - I'll try to dig out the threads from when I got caught out by this one fitting a Mondeo alternator to the Range Rover later. Haven't got time right now. Quote Link to comment Share on other sites More sharing options...
NikolaiV Posted February 16, 2008 Author Share Posted February 16, 2008 Thanks for the advice guys - have made the big cut and stitched the two part-looms together. On the tacho front there is a nice wee note attached to the blue wire saying 'coil -ve terminal) so i think only the efi RRC have a feed for the tacho from the alternator? My big question is now whether the fuel and temp gauges will work. (all idiot and dash lights are working nicely). As the original dash had a seperate voltage stabiliser (which fed the gauges) and then feeds from the senders, i`m unsure whether the input from the senders will be appropriate for the later model gauges. There is a wee board in the top corner of the back of the dash with a few resisitors and what looks like a wee chip on it - I`m assuming that the 12V feed goes into this, then to the instruments? Do we think this will work? Quote Link to comment Share on other sites More sharing options...
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