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testing resistance on pencil coil with multimeter?
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John
Nov 14, 2011, 9:35:09 PM11/14/11
to
Does anyone know how I can test resistance on a pencil coil with a
multimeter to find out if my ignition coil is caput or not?
I'm not totally sure what I need to do to test primary and secondary
resistance.
For primary it should be 0.54 ± 0.02 ohms and...
for secondary it should be 9.0 to 12.5 kohms
On my multimeter I am setting it at 200 Ω but I can only get a reading
when I am sticking my red and black probe on the positive and negative
pins where the power connector goes onto of 1.5. When I try and stick
one of the probes up inside the pencil coil I get no reading.
What am I doing wrong if anything and what does the 1.5 value mean for
the positive and negative pins?
multimeter to find out if my ignition coil is caput or not?
I'm not totally sure what I need to do to test primary and secondary
resistance.
For primary it should be 0.54 ± 0.02 ohms and...
for secondary it should be 9.0 to 12.5 kohms
On my multimeter I am setting it at 200 Ω but I can only get a reading
when I am sticking my red and black probe on the positive and negative
pins where the power connector goes onto of 1.5. When I try and stick
one of the probes up inside the pencil coil I get no reading.
What am I doing wrong if anything and what does the 1.5 value mean for
the positive and negative pins?
John
Nov 14, 2011, 9:52:59 PM11/14/11
to
to 20k setting.
The first coil has a value of 1.5 on the primary and about 10 on the
secondary.
The second coil has a valye of 1.0 on the primary and between 9 and 14
on the secondary.
How do I interpret the values for the primary and how do I know which
one is likely to be the failed coil? I have an idea which one it is
but from the data how is it possible to know?
Mrcheerful
Nov 15, 2011, 2:35:57 AM11/15/11
to
John wrote:
> On Nov 15, 2:35 am, John <umdung...@yahoo.com> wrote:
>> Does anyone know how I can test resistance on a pencil coil with a
>> multimeter to find out if my ignition coil is caput or not?
>>
>> I'm not totally sure what I need to do to test primary and secondary
>> resistance.
>>
>> For primary it should be 0.54 ą 0.02 ohms and...
> On Nov 15, 2:35 am, John <umdung...@yahoo.com> wrote:
>> Does anyone know how I can test resistance on a pencil coil with a
>> multimeter to find out if my ignition coil is caput or not?
>>
>> I'm not totally sure what I need to do to test primary and secondary
>> resistance.
>>
>> for secondary it should be 9.0 to 12.5 kohms
>>
>> On my multimeter I am setting it at 200 ? but I can only get a
>>
>> reading when I am sticking my red and black probe on the positive
>> and negative pins where the power connector goes onto of 1.5. When I
>> try and stick one of the probes up inside the pencil coil I get no
>> reading.
>>
>> What am I doing wrong if anything and what does the 1.5 value mean
>> for the positive and negative pins?
>
> Ignore me! I think I have got the secondary as well now by switching
> to 20k setting.
>
> The first coil has a value of 1.5 on the primary and about 10 on the
> secondary.
>
> The second coil has a valye of 1.0 on the primary and between 9 and 14
> on the secondary.
>
> How do I interpret the values for the primary and how do I know which
> one is likely to be the failed coil? I have an idea which one it is
> but from the data how is it possible to know?
from the figures you give (assuming that your secondary figure is in
>> and negative pins where the power connector goes onto of 1.5. When I
>> try and stick one of the probes up inside the pencil coil I get no
>> reading.
>>
>> What am I doing wrong if anything and what does the 1.5 value mean
>> for the positive and negative pins?
>
> Ignore me! I think I have got the secondary as well now by switching
> to 20k setting.
>
> The first coil has a value of 1.5 on the primary and about 10 on the
> secondary.
>
> The second coil has a valye of 1.0 on the primary and between 9 and 14
> on the secondary.
>
> How do I interpret the values for the primary and how do I know which
> one is likely to be the failed coil? I have an idea which one it is
> but from the data how is it possible to know?
thousands of ohms) they are both giving sensible readings, however coils
break down such that their internal insulation becomes poor, so until they
are actually running and giving sparks you cannot tell if they are ok
without an expensive test rig. The best (easiest, quickest) way of testing
a coil is by substitution.
Chris Whelan
Nov 15, 2011, 4:20:19 AM11/15/11
to
very rare failure mode, you can't test a coil with a multimeter.
Some cars (VW et al) give a feedback signal to the ECU to "say" they have
fired; in the event of a misfire it will be logged. If your car does not
do that, and/or you don't have a fault code reader, you need to follow Mr
C's advice and do it by trial and error.
Chris
--
Remove prejudice to reply.
Barry
Nov 15, 2011, 4:52:43 AM11/15/11
to
to turn when in use. You really need a dynamic tester.
Barry
Nov 15, 2011, 7:13:21 AM11/15/11
to
coils. You stuff a square wave in one end of the coil and see if the
resultant waveform is damped. If so it indicates shorting turns. A bit
technical but if you know an electronics buff they should be able to do
it for you.
Grimly Curmudgeon
Nov 15, 2011, 7:17:05 AM11/15/11
to
On Tue, 15 Nov 2011 09:20:19 GMT, Chris Whelan
<cawh...@prejudicentlworld.com> wrote:
>Unless either the primary or secondary has gone open circuit, which is a
>very rare failure mode, you can't test a coil with a multimeter.
Indeed so. Several times I've had coils which tested ok on a DVM but
<cawh...@prejudicentlworld.com> wrote:
>Unless either the primary or secondary has gone open circuit, which is a
>very rare failure mode, you can't test a coil with a multimeter.
were below par or non-working in situ. About the only thing a DVM can
tell you is continuity or the basic ohmage is close to what it should
be (which can be useful in itself).
Harry Bloomfield
Nov 15, 2011, 8:57:13 AM11/15/11
to
John expressed precisely :
resistances you would need a m-Ohm meter, which are quite expensive.
There is also not way for you to check if the coil's insulation is
breaking down under voltage.
Really the only sensible way to test a coil, is by substitution with a
known good one.
--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
> How do I interpret the values for the primary and how do I know which
> one is likely to be the failed coil? I have an idea which one it is
> but from the data how is it possible to know?
Your meter is not adequate to the task, to measure sub one Ohm
> one is likely to be the failed coil? I have an idea which one it is
> but from the data how is it possible to know?
resistances you would need a m-Ohm meter, which are quite expensive.
There is also not way for you to check if the coil's insulation is
breaking down under voltage.
Really the only sensible way to test a coil, is by substitution with a
known good one.
--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk
Andy Cap
Nov 15, 2011, 4:22:11 PM11/15/11
to
On Tue, 15 Nov 2011 07:35:57 -0000, "Mrcheerful" <nbk...@hotmail.co.uk> wrote:
>from the figures you give (assuming that your secondary figure is in
>thousands of ohms) they are both giving sensible readings, however coils
>break down such that their internal insulation becomes poor, so until they
>are actually running and giving sparks you cannot tell if they are ok
>without an expensive test rig. The best (easiest, quickest) way of testing
>a coil is by substitution.
>
From your experience, do these coils sometimes fails after a run i.e. @ 50
>from the figures you give (assuming that your secondary figure is in
>thousands of ohms) they are both giving sensible readings, however coils
>break down such that their internal insulation becomes poor, so until they
>are actually running and giving sparks you cannot tell if they are ok
>without an expensive test rig. The best (easiest, quickest) way of testing
>a coil is by substitution.
>
miles ? I ask, because my Rover has twice, but some months apart, started
misfiring but it has soon cleared itself.
I popped in two second-hand coils at the weekend and it began doing somewhat
similar misfiring every time I tried to pull away. I'm wondering if mine are
somewhat marginal !
I'm reluctant to buy two new ones and it not be the problem. Would any garage be
able to test them independently?
Cheers
Harry Bloomfield
Nov 15, 2011, 6:21:17 PM11/15/11
to
Andy Cap laid this down on his screen :
>
> I popped in two second-hand coils at the weekend and it began doing somewhat
> similar misfiring every time I tried to pull away. I'm wondering if mine are
> somewhat marginal !
They could be marginal, but it is unlikely that all would be marginal.
I would look elsesware if all coils exhibit the same fault - Check
plugs, HT leads and distributor cap.
>
> I'm reluctant to buy two new ones and it not be the problem. Would any garage
> be
> able to test them independently?
The normal test method is substitution with known good components. If a
cylinder is missing, try unplugging the HT from one cylinder at a time,
until the misfire doesn't get worse by unplugging - that then is the
cylinder with a misfire.
> From your experience, do these coils sometimes fails after a run i.e. @ 50
> miles ? I ask, because my Rover has twice, but some months apart, started
> misfiring but it has soon cleared itself.
They can fail when they get hot, yes.
> miles ? I ask, because my Rover has twice, but some months apart, started
> misfiring but it has soon cleared itself.
>
> I popped in two second-hand coils at the weekend and it began doing somewhat
> similar misfiring every time I tried to pull away. I'm wondering if mine are
> somewhat marginal !
I would look elsesware if all coils exhibit the same fault - Check
plugs, HT leads and distributor cap.
>
> I'm reluctant to buy two new ones and it not be the problem. Would any garage
> be
> able to test them independently?
cylinder is missing, try unplugging the HT from one cylinder at a time,
until the misfire doesn't get worse by unplugging - that then is the
cylinder with a misfire.
Mrcheerful
Nov 15, 2011, 6:28:08 PM11/15/11
to
are good)
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