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Dunno. Hope you are right though..I suppose I could put a known-ish load, like a headlight, through it as a rough check.
It was moderately expensive,( about 30 quid IIRC) but of course it isn't a Fluke. It was recommended by a British mechanic that runs a car-sourcing business here. Taiwanese model (YF-3502T), which probably wouldn't be familiar to you.
https://www.eclife.com.tw/ups/moreinfo_38558.htm
OTOH its instructions (which I've lost) were all in Chinese, and I've never done this before, so its quite possible I did it wrong, or (probably even more likely) there's something left on I'm not aware of.
Maybe the heated rear screen, which I think is broken but the indicator light for it .shows up on the dash sometimes.
I could try it with a test light but if it really is 4 amps it'd have to be something expendable. I think I have some Christmas tree lights somewhere.
Edited by edlithgow on 25/05/2020 at 16:19
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I presume that as well as switching to the 20A range, you also have the leads in the extreme LH jack and the centre common jack?
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Think so, though I'll double check that the next time I look at this. Have to do some work now though.
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Current Drain Load Testing
No known load 4.2-4.6
+ brakes 7.3-7.5
+ sidelights 7.5-7.6
+ dipped beam 13.76
+ LH indicators 7.8 - 8.0 (Too fast, prob fault)
+ RH indicators 8.0 - 10.0
Looks like the meter is responding to additional applied load pretty much as I would expect. Decided not to try full beam.
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Successively removing fuzes 1 to 5 has no effect on the 4.4-4.6 Amp current.
Removing fuze 6 drops current to 4,0 amps
Removing fuze 7 drops it to 3.4 amps,This current is unaffected by removal of the remaining 3 fuzes.
However, the points were in contact. Moving them apart with a pen tip drops the current to 1.1-1.4 amps, which is roughly the same as the reduction achieved by removing all the fuzes.
So it seems the ignition system draws about 3.4 amps via the points, and the fuzed circuits draw about 1.2 amps.
This may be normal
https://www.aa1car.com/library/electrical_amp_loads.htm
"Ignition Coil (single oil-filled coil older vehicle) - 3 to 4 amps"
or even a bit low
"Ignition System (primary circuit) - 6 to 20 amps."
Edited by edlithgow on 26/05/2020 at 09:40
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I'm not sure what the OP is trying to prove. The current draw with ignition off is zero. That's what you would expect. With ignition on it's several amps. That's what you'd expect too. It proves that if you left the car with the ignition on the battery would soon be discharged. That's also to be expected. This does not mean you have any wiring faults. Every electrical component on the vehicle will draw current when it's switched on. That's a good way of telling it's working. If you had a wiring short you'd either have repeatedly blowing fuses or burnt wiring. The amount of current being drawn you mention with the ignition on is perfectly normal.
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The amount of current being drawn you mention with the ignition on is perfectly normal.
I didn't know that,
Now I do.
I might have learned it a bit earlier if I hadn't been told above that my "perfectly normal" readings were due to a faulty meter, but alls well that ends well.
I suspect some problems with the cars electrical systems because the battery seems to drain faster than I'd expect, but intermittently, I get the the charging/battery light and/or heated rear scrreen light coming on, also intermittently,the temperature indicator doesn't work, and most recently I was unable to get the radiator fan control working even with direct jumpering, though the block temperature sensor and relay seem to check out OK.
Basic charging function checks out OK with a multimeter. Its been suggested on here earlier that I'd need an oscilloscope for further checks.
The fan control is to be investigated further if/when I remember where I put the relay, and if/when it stops raining, which it usually does in late October/early November..
Edited by edlithgow on 27/05/2020 at 02:32
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I suspect some problems with the cars electrical systems because the battery seems to drain faster than I'd expect, but intermittently, I get the the charging/battery light and/or heated rear scrreen light coming on, also intermittently,the temperature indicator doesn't work, and most recently I was unable to get the radiator fan control working
The fan control is to be investigated further if/when I remember where I put the relay, and if/when it stops raining, which it usually does in late October/early November..
If that car of yours was a dog, I'd consider having it put down!
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I suspect some problems with the cars electrical systems because the battery seems to drain faster than I'd expect, but intermittently, I get the the charging/battery light and/or heated rear scrreen light coming on, also intermittently,the temperature indicator doesn't work, and most recently I was unable to get the radiator fan control working
The fan control is to be investigated further if/when I remember where I put the relay, and if/when it stops raining, which it usually does in late October/early November..
If that car of yours was a dog, I'd consider having it put down!
If that car of mine was a dog, it wouldn't be your dog, so you would be well advised to leave it alone.
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Basic charging function checks out OK with a multimeter. Its been suggested on here earlier that I'd need an oscilloscope for further checks.
In most cases checking the charge rate with a voltmeter will tell you everything you need to know. If the battery voltage with the engine running is 14.4v then it's very likely if not certain that the charge rate is absolutely fine. Then I would start adding loads, starting with the headlamps, then heated rear screen, heater blower, fog lamps etc, but not indicators. This is because they flash and you'll have wandering readings which can then confuse you a bit. With all loads on the charging voltage should read around 13.5v with the engine above idle. An alternator output will be at its maximum at around 1,200rpm, so there is no need to rev it higher than that. You'll see that if you do the charging voltage will not increase, or if it does it'll be negligible. If these results are achieved then the charging system is fine.
The other way is to use an ammeter. But before you connect yours up you should understand that most multimeters are fuse rated at 10A maximum, and so they are not suitable for this test. You will damage your meter if you use the ammeter function for testing the charge rate. What you need is an inductive current clamp. It clamps around any cable and measures the current drawn along it by converting the electromagnetism into a current reading in amps. These often range up to 1,200A and are perfectly suitable for this test.
There are two ways to do this. Firstly notice that your current clamp is directional. It will have an arrow on it showing the direction of current from positive to negative. Be sure to position the clamp the correct way so that the arrow points in the direction of current flow.
1. Place the clamp around the alternator main cable and start the engine. The clamp will read the alternator output in amps. Increase the engine speed to 1,200rpm until the reading stops increasing. Then start switching on loads until everything is switched on (except indicators for none other than the reason I mentioned earlier). Now you will see the total load placed upon the alternator in amps. What you need to factor in is the condition of the battery which you won't know. If the battery is in good condition but discharged it will draw more current which will be added to your reading. If the battery is fully charged it will draw less because it won't need it.
2. The other method is to clamp either all of the battery positive cables or negative cables. It doesn't matter which as long as you connect the clamp pointing in the direction of current flow. If you get it wrong you will do no harm, you'll just have reversed readings. Start the engine and initially see that the current reading is heavily in the minus. This is the starter motor drawing current. As soon as the alternator starts charging the reading will change to a positive. What you need to remember here is that there are two things going on. The cables together are bi-directional. Current is being drawn by components that are switched on, whilst at the same time the battery is drawing current in the opposite direction from the alternator. What your current clamp is reading is the difference which is the amount of current drawn by the battery. Whatever this figure is (as long as it's positive) will tell you how good of not the battery is. A healthy battery should draw around 10A - 15A, but this is not a set figure. If the current difference is very small, say 5A or less, or very high say 25A or more then it's very likely that the battery is not serviceable. But for the purposes of checking the charge rate if the current reading is positive then the charging system is working.
Hope it helps.
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Thanks for that very full explanation.
In retrospect, although the meter I have is, I think, a fairly good one as basic meters go, I should have spent a bit (probably 3-5 times) more and either got one with special automotive functions such as Tach and Dwell, or got one with inductive clamp current measurement (Or both, though that might be hard to find)
I'm putting off spending the money for now, since its always possible I might have to have the car "put down".
Current priority is to get the fan temperature control sorted, which was beset with puzzling apparent randomness on the first attempt (making me suspect loom shorts) , such that I gave up and installed a manual control.
This got through the inspection but if I carry on using it I'm going to forget and cook the engine and/or flatten the battery. Close shaves already.
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A car this age has a simple ignition circuit, it may even have contact points rather than a sensor which mimics contact points.
Ignition on, engine off the ignition coil will probably take about 3-4 amps with the contacts closed.
Disconnect the ignition coil supply lead and re measure.
The Ecu, if it has one, will account for about 1 to 2 amps. 1986 electronics are not CMOS low power. The dash lights will be filament bulbs, each warning light will be at least a 1.2w bulb. Alternator voltage regulator will be full on when stood, again maybe 0.5 amp or more. It may be an old fashioned relay regulator. Even more current drain.
Even modern cars draw several amps with ignition on and engine not running
Edited by brum on 27/05/2020 at 17:19
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Oh and I forgot about the fuel sender/gauge, temperature gauge etc all require current.
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