Ohm resistance meter reading help

(RIP) Bobble

(RIP) Bobble

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Hi Peeps

Just wondered if anybody could help me please? I'm trying to do an Ohm resistance reading from the coil on my 1150 (twin spark), the Clymer manual say's it should be 0.87ohm. My meter has a 2000 setting, on this I get a reading of 1 before doing anything, then a reading of 007 ohm on the meter when testing the coil, would this be 0.007 or 0.07 or just 70 etc (no dot)

Sorry to be a thicky, I have finally confused the hell out of myself :blast
 
Testing such low resistances actually requires some pretty good equipment. In your case, you could touch the two test probes together and make sure it reads zero. If not, you can subtract that reading from any subsequent tests.

If you get any reading below 10 you aren't that far out. Best thing to do is compare both your coils or against a known good one.

The 0.87 ohms you're trying to measure is less than the least significant digit on your meter and - even if you pay 10 grand for a meter - no-one will quote accuracies at that level.

Most coil failures are normally in the secondary windings anyhow, either a shorted turn or an insulation fault.

hth
Dick
 
uncle dick said:
Testing such low resistances actually requires some pretty good equipment. In your case, you could touch the two test probes together and make sure it reads zero. If not, you can subtract that reading from any subsequent tests.

If you get any reading below 10 you aren't that far out. Best thing to do is compare both your coils or against a known good one.

The 0.87 ohms you're trying to measure is less than the least significant digit on your meter and - even if you pay 10 grand for a meter - no-one will quote accuracies at that level.

Most coil failures are normally in the secondary windings anyhow, either a shorted turn or an insulation fault.

hth
Dick
Click to expand...

Thanks Dick

If I touch the probes together it does indeed read 0, but I couldn't figure out what my 007 reading was, as in 7, .7 or .007 as it now sounds like. How are you supposed to check these things then? Unfortunately (or fortunately as cost goes) there is only one main coil on the twin spark (besides the coil sticks). so I guess I'm going to have to get one just to find out if my eliminations have led me to the right part being faulty. All a learning curve :thumb2
 
What's your symptom - I'm guessing loss of spark on both secondary plugs if that's the coil you're trying to test and there's one of them so it must be a wasted spark setup?

Is there a pulse on the low tension side of the coil when the engine turns (might be able to see that on a multimeter, the needle used to twitch on old analogue multimeters but a digital one might not react to the short-duration change in voltage). If not, the problem is before the coil.

Can you get a spark by putting an earthed plug on the end of the lead and putting 12v through the coil primary briefly (e.g. brush the end of a piece of wire rapidly across the +ve battery terminal)? Plug should spark as the primary circuit disconnects.

Is your fault intermittent? Beware: if you don't understand what I'm suggesting above (or you do but you're touching the wrong things at the wrong time) you're liable to get an almighty shock.

Can you find an automotive electrician (or maybe a motor factors) that has a coil tester? They might be able to tell you whether the one you've got works or not for much less than the cost of a replacement.
 
The reason for the test is:
Bike running rough, will tick over however when trying to increase revs it gets very lumpy/firing on left cylinder, right down pipe cool 'ere' to touch left hot, have swapped coil sticks over with no change, right hand primary and secondary plugs are sparking but I believe week spark, plugs very wet. Have pulled off HT lead from right and bike continues to tick over, pull left ht lead off and the bike stops.

Only thing to do is swap over spark plugs (thought about this once I got in tonight:blast) just incase the right is not working under load, otherwise I think it's a week spark on right. Hence trying to do a main coil test, I don't think the hal sensor would reduce spark to one side? :nenau
 
I might be wrong, but I get the impression that each cylinder will run on either primary or secondary alone. Is your left primary (either coil stick or plug) not firing - sounds like the left pot dies when you pull the secondary HT lead off whereas the right doesn't? Does that swap sides when you swap the coil sticks over?
 
Bobble said:
The reason for the test is:
Bike running rough, will tick over however when trying to increase revs it gets very lumpy/firing on left cylinder, right down pipe cool 'ere' to touch left hot, have swapped coil sticks over with no change, right hand primary and secondary plugs are sparking but I believe week spark, plugs very wet. Have pulled off HT lead from right and bike continues to tick over, pull left ht lead off and the bike stops.

Only thing to do is swap over spark plugs (thought about this once I got in tonight:blast) just incase the right is not working under load, otherwise I think it's a week spark on right. Hence trying to do a main coil test, I don't think the hal sensor would reduce spark to one side? :nenau
Click to expand...

If the fault doesnt move from left to right when swapping the sparky stuff over, could be that the problem is elsewhere. It may be worth checking the connections to the injectors and cleaning them up a bit if you see any corrosion.

Nick
 
The left pot is obviously running fine and the stick coils both seem to be OK as you've already swapped those around.

I think that both sets of HT circuits are lost spark so everything else is common and ergo should be good.

Try swapping the injectors as wet plugs on the right suggest that it could be a leaky injector.

What is the mileage?
 
Well I changed the plugs and it started better, even ran when alternate coil stick/ht leads pulled off. I've now got the bike on a optimate to fully charge the battery as it's taken a hammering. Will report back soon..
 
uncle dick said:
Testing such low resistances actually requires some pretty good equipment. In your case, you could touch the two test probes together and make sure it reads zero. If not, you can subtract that reading from any subsequent tests.

If you get any reading below 10 you aren't that far out. Best thing to do is compare both your coils or against a known good one.

The 0.87 ohms you're trying to measure is less than the least significant digit on your meter and - even if you pay 10 grand for a meter - no-one will quote accuracies at that level.

Most coil failures are normally in the secondary windings anyhow, either a shorted turn or an insulation fault.

hth
Dick
Click to expand...

What he said - you cannot make accurate low resistance measurements with a 'normal' multimeter. To get an accurate measurements down to 0.87 Ohms you will need a dedicated milli-ohmeter that makes a 4-terminal resistance measurement, and they are not cheap.
 
Engineer said:
What he said - you cannot make accurate low resistance measurements with a 'normal' multimeter. To get an accurate measurements down to 0.87 Ohms you will need a dedicated milli-ohmeter that makes a 4-terminal resistance measurement, and they are not cheap.
Click to expand...

Ask any electrician, they are required to have calibrated continuity meters, cost about £200 and calibrated annually they read to two decimal places and down to 0.01ohm with high accuracy. Things have moved on with meters in the last decade.
I use one like this

http://www.ebay.co.uk/itm/Megger-BM...Equipment_ET&hash=item43ab6206dd#ht_500wt_949
 
I use a digital ohmeter and I get 0.5 ohms on the primary winding and 13 kohms on the secondary winding. No need for expensive equip. to see a faulty coil...

Dan.
 
warmshed said:
Ask any electrician, they are required to have calibrated continuity meters, cost about £200 and calibrated annually they read to two decimal places and down to 0.01ohm with high accuracy. Things have moved on with meters in the last decade.
I use one like this

http://www.ebay.co.uk/itm/Megger-BM...Equipment_ET&hash=item43ab6206dd#ht_500wt_949
Click to expand...


I stand corrected! these things can compensate for the test lead resistance but they do cost £200 squid and need to put a relatively high current through the resistance being measured. Depends whether you think £200 squid is expensive or not.
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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