19 replies to this topic

[TerrA LX]

I tested a module to compare to fuzzypumpers findings and not sure whats what.

FYI my volt meter on continuity check reads mV.

as in first test
15 neg and 16 pos FP result 1. mine 1475mV
second
15 pos and 16 neg Fp result .623 mine 986mV
third
1 pos and 7 neg FP result 1. mine 1850mV
fouth
1 neg and 7 pos FP result 1. mine 1852mV

and on and on.
I have a very weak spark so is that current with my results?

[FastEHHolden]

We talking the black bosch module in a Blue motor HEI?

http://holdenpaedia....n.com/Bosch_HEI

That will help somewhat...but it doesn't answer you specific questions...the trouble shooting section might help.

[TerrA LX]

Hmm, coil might be weak

Original question was in relation to the meter readings in this thread

[TerrA LX]

Fuzzy???

[VitcLJ]

Sorry not Fuzzy just an old f@!#wit Electronics specialist

The problem here is that electronic multimeters unfortunately are not created equal.

Fuzzy's meter when its showing the 1. on the left means its not seeing anything resistance wise on the selected scaling (overscale.)
Most of the cheap multimeters just set the continuity range to the lowest resistance range and turn on a beeper for anything below generally about 50 ohms.

Even high class meters like Fluke can catch you out as some of the top line ones (model 87III and 87V comes to mind)impress different voltages onto the probes when in resistance range the 87III is 1.3V and the 87V is 7.9V across open circuited terminals thus when using them for measurement in semiconductor circuitry (like the ignition module)you get completely different values. (can be a real puzzler when you first come across it ).
So basically unless you have a meter same as fuzzy its all a little academic.
Have just measured a known good module with the top of the range dick smith Elcheapo and get the following
Ground connected to positive meter lead: to 16 5.7Megohm, to 15 588 ohm to 7 13.8Megohm to 3 19.7Kilohm
Ground connected to negative meter lead: to 16 opencirc, to 15 588 Ohm to 7 17.2Megohm to 3 19.7kilohm
from 16 to 15 with 16 connected to neg 1.1 megohm with 16 connected to pos open circuit.
From 15to 7 both ways 1.1megohm
from 15 to 3 both ways 1.0megohm
from 3 to 7 14meg ohms
I would like to point out that these readings are with a Dick smith Q-1429 el cheapo meter and that these readings may not be obtained on a meter with a different voltage on the resistance reading scales so basically they may help you if your meter can read resistance or they may not.
Else if your meter has a diode range and you use this you should get similar results to fuzzy at least from terminals 15 16 and ground. I do with my cheapy.
see a diode between 15 and 16, 15 and ground, and 16 and ground. (reads 560 roughly one way and overscale otherway)

hope this helps

[TerrA LX]

Sorry not Fuzzy just an old f@!#wit Electronics specialist


hope this helps

If it takes being a frOckwit to undedrstand it ten so be it.
Makes sense now, just like oil's ain't oil's eh? ha ha.

Else if your meter has a diode range and you use this you should get similar results to fuzzy at least from terminals 15 16 and ground. I do with my cheapy.


hope this helps

I used the same setting as fuzzy, are his readings in mV too?

I do with my cheapy.
see a diode between 15 and 16, 15 and ground, and 16 and ground. (reads 560 roughly one way and overscale otherway)

hope this helps

Are ther mV?


Also I assume if I get a reading and you guys get oversacle then the main thing is getting a reading and not a short?

[VitcLJ]

sorry had to go way and watch Top Gear then walk the dog.
Dont think Fuzzy's reading in mV looks more like the usual resistance scale. Do you have the same Digitech meter? If you use the diode scale (if you have it) readings are usually roughly mV that is you will see about 600mV when diode conducts (500 to 700 on most meters they are only approximate) and over-range or open circuit the other way. that is basically what Fuzzy's metering is showing (some meters use the diode scale as continuity scale and put a buzzer on it that goes off if the reading is low enough. As you can see my meter gives 558 ohms on the resistance scale which scales to 558mV across the terminals (closely matches the diode range readings) but not all meters do that on the resistance scales (I could get all technical and long winded here but it wont help you sort this problem), the only trustworthy one on most meters is the diode range.
The diode test range on meters usually is a little better for testing these types of things as they can provide a larger current through the semiconductor to stabilise the readings and have the voltage at the test terminals to turn on the diodes.
AS you say oils aint oils and meters vary considerably particularly at the cheap end of the market. If you want accuracy and stability you have to pay for it.

[TerrA LX]

sorry had to go way and watch Top Gear then walk the dog.

No problem, I will digest this and will try a few more tests and get back to you tomorrow and hopefully learn something new in the process.
Cheers T.

[fuzzypumper]

My meter was in continuity / diode test mode and should therefore have been showing mV.
So where the meter shows -1 then the reading was overscale, greater than 2mV across the terminals.

There's really no point measuring in resistance mode because if you get 1megohm vs 10megohm ,
no difference. You may as well call it an Open circuit.

Having said that I did mention in the document that these are really passive tests and will only tell you
if there is something majorly wrong with module. Its likely not to show up issues like poor pickup, eratic timing
or low spark. Although with low spark, I would be looking at your coil first.

There is also the issue of which revision module you have i.e. the last 3 digits 016, 017, 021, 024
because the change in revision can denote a change in circuit design and therefore may give a different reading
to what I documented.

Edited by fuzzypumper, 09 March 2010 - 10:09 PM.

[TerrA LX]

Ok thanx fuzzy, firstly I was trying to establish what my readings meant compared to yours, I was testing in the cont/beep mode and it was reading mV. Secondly I flashed the coil on the battery and was only getting a little blue/orange spark, prolly not enough to fire under compression even tho the coil tested good on the meter.

[fuzzypumper]

What sort of resistance readings do you get from the coil?

[TerrA LX]

I meant my mV readings were for the module.

I didn't write down the coil resistance so will re check tomorrow.

[TerrA LX]

I am getting a 0.00 reading from the primary now

FYI my meter is Micronta.

[fuzzypumper]

Well I would have expected to see around 1 ohm, not a straight short circuit of 0 ohms.
Which brings me to my next question, are you sure you are on the lowest ohms reading on the scale?
because I cant believe your multimeter is gonna show down to 2 decimal places of an ohm.

[TerrA LX]

:Headbang2:On the wrong range (20K),
1.8 on the 200 range.
0.001 on the 2k range

secondary showing 7.96 on the 20k range.
Overscale on the lower ranges.

[fuzzypumper]

Well that seems about right, but the proof would be to try another coil.
A blue/orange sparks suggests a high enough voltage but what dod you call little?
Did you have a spark plug on the end ?

[TerrA LX]

Did you have a spark plug on the end ?

Yep.

Spark was more like a flint rather than a nice blue crack.

[fuzzypumper]

I took some video and captured snaps of a Faulty HEI epoxy bosch coil and Good Oil Type HEI Bosch Coil.
I need to figure out how to convert and upload video some where so you can see and hear the spark difference.
I used a an electronic dizzy on the bench.

Faulty HEI epoxy bosch coil spark- Ths coil wouldnt spark once it heated up in car.


Good Oil Type HEI Bosch Coil

Edited by fuzzypumper, 11 March 2010 - 05:24 PM.

[TerrA LX]

Yeah I am not getting the big cracking sound of a nice fat blue spark.

[TerrA LX]

Some more findings in regards to power supply, when running the correct coil make sure you have at least 11V plus at the + side of the coil both cranking and running.
Also you need a coil with a primary resistance between terminals + (15) and - (1) = 0.5 - 0.7 ohms at 25degC
and
secondary between terminal - (1) and HT coil lead connection (4) = 5 - 7 Kilohms to gain the best performance, less, especially on the primary will lead to a weak spark that you will never tune out.