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Post by Deleted on Apr 23, 2021 18:37:06 GMT
A lot.
They are making me rich beyond the dreams of Everest.
And I'm not referring to double glazing here.
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Post by Deleted on Apr 23, 2021 19:41:55 GMT
Thanks - at least gives me somewhere to start looking.
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Post by tonyb on Apr 23, 2021 19:50:34 GMT
I can't make much sense out of that because it seems like its missing pulses from the alternator. There are probably two thin wires on the back of the alternator. One is the warning lamp connection and one the pulse feed to the rev counter. Don't touch any thick wires but make sure both thin wires are properly terminated, clean and tight on the alternator. The one in question may be marked W.
If you have a multi-meter that will measure Hz (frequency) try measuring the frequency between the W terminal and any negative. It should steadily rise as you rev the engine and the drop as you decelerate. If it does so steadily then the alternator is probably OK.
You can get some idea by using the voltage scale. Again you will be looking for an even and steady rise and fall but not over such a large range, maybe only mVs.
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Post by Trina on Apr 23, 2021 20:38:20 GMT
I actually thought Rev Dial not working was a vicar who'd lost his job.π
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Post by Deleted on Apr 23, 2021 20:42:44 GMT
Tony is nearly there - set multimeter to AC; you should see around 6-7 v AC if I remember correctly.
Often the cause of erratic or no reading is a knackered brush pack on the alternator - if it uses the starter alt to get its reading chances are itβs on its way out.
Check you have continuity on the signal (W terminal) wire and a good clean secure connection at the alternator stud/terminal
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Post by tonyb on Apr 23, 2021 20:49:45 GMT
Tony is nearly there - set multimeter to AC; you should see around 6-7 v AC if I remember correctly. Often the cause of erratic or no reading is a knackered brush pack on the alternator - if it uses the starter alt to get its reading chances are itβs on its way out. Check you have continuity on the signal (W terminal) wire and a good clean secure connection at the alternator stud, The pulses are half-wave rectified so although the actual readings will not be accurate DC will certainly read and I think AC will as well. Should be fine to see if the voltage rises.
I agree about the brushes but in this case 700 rpm seems to me to indicate a serious loss of pulses AND its consistent over at least two starts, hence I suspect its a very loose blade connection on W.
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Post by Deleted on Apr 23, 2021 20:50:58 GMT
Tony is nearly there - set multimeter to AC; you should see around 6-7 v AC if I remember correctly. Often the cause of erratic or no reading is a knackered brush pack on the alternator - if it uses the starter alt to get its reading chances are itβs on its way out. Check you have continuity on the signal (W terminal) wire and a good clean secure connection at the alternator stud, Thanks.
First question - how do I identify the w terminal? Off to bed shortly so don't expect photos for now. If it is easy to explain please do, if not I'll post a photo tomorrow.
G'night.
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Post by Deleted on Apr 23, 2021 20:54:04 GMT
Tony is nearly there - set multimeter to AC; you should see around 6-7 v AC if I remember correctly. Often the cause of erratic or no reading is a knackered brush pack on the alternator - if it uses the starter alt to get its reading chances are itβs on its way out. Check you have continuity on the signal (W terminal) wire and a good clean secure connection at the alternator stud, The pulses are half-wave rectified so although the actual readings will not be accurate DC will certainly read and I think AC will as well. Should be fine to see if the voltage rises.
I agree about the brushes but in this case 700 rpm seems to me to indicate a serious loss of pulses AND its consistent over at least two starts, hence I suspect its a very loose blade connection on W.
I'm fairly certain it is something I dislodged today - all working perfectly until then.
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Post by Telemachus on Apr 23, 2021 22:02:28 GMT
These types of Rev counters are servoed - they need 12v dc power as well as the ac signal from the alternator. If the latter had failed it would be showing zero. But it isnβt, so nothing to do,with the signal from the alternator, it is either lacking the 12v supply or itβs knackered.
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Post by tonyb on Apr 24, 2021 6:53:09 GMT
Just checked.
Engine off - 700
Key switch in first position with buzzer sounding - 0
Engine started - 700
Note - reads zero with the ignition switch turned on but when started sticks at 700 rpm so it looks to me as if the 12v supply is OK< that only leaves the alternator or a poor connection.
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Post by tonyb on Apr 24, 2021 6:58:37 GMT
Tony is nearly there - set multimeter to AC; you should see around 6-7 v AC if I remember correctly. Often the cause of erratic or no reading is a knackered brush pack on the alternator - if it uses the starter alt to get its reading chances are itβs on its way out. Check you have continuity on the signal (W terminal) wire and a good clean secure connection at the alternator stud, Thanks.
First question - how do I identify the w terminal? Off to bed shortly so don't expect photos for now. If it is easy to explain please do, if not I'll post a photo tomorrow.
G'night.
As I said, you have one or two thick wires on your alternator, leave theses alone. With a rev counter you will typically have two other thin wires.
One comes from the warning lamp while the other goes to the rev counter. Check both have nice tight and clean connections and that the terminals are properly crimped to the cables.
If you want to be more accurate leave the ignition turned on and disconnect each thin wire in turn. The one that puts the charge warning lamp out is not the rev counter (W) terminal, the other one is.
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Post by JohnV on Apr 24, 2021 7:34:30 GMT
To quote Andrew "buggered innit"
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Post by Telemachus on Apr 24, 2021 7:37:32 GMT
Just checked.
Engine off - 700
Key switch in first position with buzzer sounding - 0
Engine started - 700
Note - reads zero with the ignition switch turned on but when started sticks at 700 rpm so it looks to me as if the 12v supply is OK< that only leaves the alternator or a poor connection.
Oh yes youβre right, I missed the middle one! But I still canβt see how it could be something to do with the alternator or W terminal wiring, how could it be receiving a signal corresponding to 700rpm regardless of engine rpm? I think it must be the actual instrument.
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Post by tonyb on Apr 24, 2021 8:00:22 GMT
Note - reads zero with the ignition switch turned on but when started sticks at 700 rpm so it looks to me as if the 12v supply is OK< that only leaves the alternator or a poor connection.
Oh yes youβre right, I missed the middle one! But I still canβt see how it could be something to do with the alternator or W terminal wiring, how could it be receiving a signal corresponding to 700rpm regardless of engine rpm? I think it must be the actual instrument. I am also very unsure about how that steady 700 rpm could occur but I have seen some very odd readings from the rev counter on a Ford with a loose connection on W. Tightening the connection cured it.
Before condemning the instrument it's my view that simpler things should be checked first. Only once those checks have not cured the problem would I suggest it's the unit itself. The needle part of these instruments don't produce many reports of faults (unlike the hour counters) so that fact reinforces the suspicion that its probably external to the unit. The OP would be very fed up if he fitted and new unit and it still played up.
Add the fact that the OP had been working around the engine and a loose connection, especially a blade one, seems more likely than anything else. it's all too easy to loosen the female blades by inadvertently pushing on the cable, then there is the possibility of a loose crimp in a similar manner on the calbe into an eye terminal.
I hope we get feedback on what happens, in the end you may well turn out to be correct.
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Post by thebfg on Apr 24, 2021 8:03:50 GMT
Could it be getting a signal of something else like a short somewhere.
@gazza advice of testing continuity between the alternator and counter is definitely something that should be done too. Partly because that's the feature on mine that I use the mostπ
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