Temporarily Using non OE Coil - Mercedes-Benz Forum
 
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post #1 of 8 (permalink) Old 06-20-2018, 09:07 AM Thread Starter
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Temporarily Using non OE Coil

Hi guys my coil which is the transistor one for the TSZ4 system is bad.#000 158 28 03.

Question is I have to import this coil from abroad since none are left in the country, I tried an Hitachi coil I had lying around and the car fired up perfectly just kept it on for baout 10-20 seconds.

The original coil says it should have:

0.33-0.46 ohm on the primary
7-12k ohm on the secondary

This Hitachi one has

1ohm on the promary
and about 12.3k on the secondary

If I temporarily use this coil will I hurt the switching unit or anything else besides the coil itself?

Any feedback will be welcome.

Thanks!

Konrad.
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post #2 of 8 (permalink) Old 06-20-2018, 12:38 PM
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You're posting DC resistance values... a positive determination cannot be made simply by checking DC resistance. However, it goes heavily in your favor that the engine ran using the Hitachi coil.

The Hitachi primary has twice the DC resistance as the original. In a DC circuit this will result in half the current. This could mean nothing or it could be a game changer. It could be higher because the gauge of the wire is thinner, or because the gauge is the same but the primary is made of a much longer length... more turns.

Having said that... the primary is being turned on and off by the "switching unit" and being that it is switching fewer amps, all things being equal my best guess would be that you'll be OK using the Hitachi coil for now but replace it with the original or equivalent part ASAP.

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post #3 of 8 (permalink) Old 06-21-2018, 09:35 AM Thread Starter
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thanks for your detailed answer, found a used coil that matches That I'll use in the mean time!
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post #4 of 8 (permalink) Old 06-21-2018, 03:32 PM
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Doubling the primary resistance will mean that the coil will charge slower and the available energy in the coil will be lower at the first time constant. While this might work at low RPM, once you rev it up the available ignition energy will fall off.

As Jyuma says, you really need to measure the coil's inductance in mH to have the full picture.

I am using a Bosch silver coil, probably made in Brazil, which coils have a terrible reputation for reliability. I'll take its specs and if I can find an NOS blue TCI coil will measure that too.
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post #5 of 8 (permalink) Old 06-22-2018, 08:23 AM Thread Starter
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Funny thing is these coils are black magic to me now since the original non working blue transistor one I had has the same ohm values as the blue used transistor one I'm currently running. So for some reason same values but one of them works. Odd. too odd!
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post #6 of 8 (permalink) Old 06-22-2018, 10:19 AM
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Quote:
Originally Posted by Kpeters View Post
Funny thing is these coils are black magic to me now since the original non working blue transistor one I had has the same ohm values as the blue used transistor one I'm currently running. So for some reason same values but one of them works. Odd. too odd!
At the risk of boring the crap out of people... a transformer works by passing a current through the primary which results in the creation of a magnetic field. As the magnetic field builds (or collapses) the magnetic flux (lines of magnetism) cross the windings in the secondary which will create a voltage in the secondary. The amount of voltage in the secondary is a function of the ratio of turns in the primary to turns in the secondary. It is very much proportional to the degree that double the turns in the secondary will result in double the voltage in the secondary (but half the current). This effect of a current (voltage in motion) in the primary producing a magnetic field that then creates a voltage in the secondary is totally dependent upon the integrity of the coils involved. This is why simply DC resistance checks are all but useless, because the fact that the DC resistance between two different coils is the same doesn't tell you anything about the condition of the windings in the two coils.

Clear as mud?

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post #7 of 8 (permalink) Old 08-12-2019, 09:42 PM Thread Starter
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Quote:
Originally Posted by Jyuma View Post
At the risk of boring the crap out of people... a transformer works by passing a current through the primary which results in the creation of a magnetic field. As the magnetic field builds (or collapses) the magnetic flux (lines of magnetism) cross the windings in the secondary which will create a voltage in the secondary. The amount of voltage in the secondary is a function of the ratio of turns in the primary to turns in the secondary. It is very much proportional to the degree that double the turns in the secondary will result in double the voltage in the secondary (but half the current). This effect of a current (voltage in motion) in the primary producing a magnetic field that then creates a voltage in the secondary is totally dependent upon the integrity of the coils involved. This is why simply DC resistance checks are all but useless, because the fact that the DC resistance between two different coils is the same doesn't tell you anything about the condition of the windings in the two coils.

Clear as mud?
Interesting thanks! Didn't see you answer until a year later but thanks!
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post #8 of 8 (permalink) Old Today, 02:16 PM
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New member here, found these good infos while searching for coil infos... funny about the quality of the one made in Brazil coil... the other is made in West Germany... so we know how old that must be... arrrrgh...

I did the same as the OP and installed one of the spare from the 74 Jeep... it is running fine... in the driveway. I suspect a short... when the coil "heats up" after 20 min... loss of power, which is regained after a 10 min cooling period...

Cheers

Michel
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