.......So I says: My coils hooked up backward! Then he said....

364 Views 14 Replies 8 Participants Last post by 2.4T, Oct 28, 2004

2.4T

Discussion Starter · Oct 26, 2004

Can't beleive it! PO installed this coil and the car ran crappy. Took it to a dealership and they said the low tention side was connected incorrectly. That was in '02. A little while goes by and I'm fiddling with a multitester and it says my +12v is going to the -side of the coil. Sure enough, my haynes says the black wire with a white line is supposed to be on the + end. Sheez. Too bad I have the carbs off now-I want to know how much better it runs.

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Cache

· #2 · Oct 27, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

+12v SHOULD be going to the negative side of the coil if the car isn't running (Key on, of course).. With the key on, you should get voltage at both sides of the coil.. With the engine running, and a test light on the negative side of the coil, you should see the test light pulse.

chevyman

· #3 · Oct 27, 2004

Then I said..........

...........at the risk of starting a war,

it really makes no difference which side is + or -..................

There was a train of thought that indicated that the "+" side be made up with the 12V supply, and the "-" side going to ground. In certain cases a difference was noted.

In general, however, the coil consists of a simple wire connection (internally) from the + to the - posts.
As long as the coil is charged and then "sunk" to ground in order to produce a spark, the connections make little or no difference at all.

I would expect that your 'crappy' operation had nothing to do with the connections, and if, in fact the coil was causing the problem, it is for some other reason than the reversal of the + and - wiring.

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2slo4u

· #4 · Oct 27, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

Ditto Chevyman, I've never noticed a difference in the way the engine runs by reversing the coil, but supposedly it does affect spark plug wear by making the "wrong" side of the plug erode. Someone correct me if I'm wrong here.

81zxturbo
95slobaru

Cache

· #5 · Oct 27, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

That is correct for our coils, some are different.

blue

· #6 · Oct 27, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

I thought the coil had a common earth on the - side and only 3 connections thus by geometry, it is asymetrical and can only be properly installed one way.

Him

· #7 · Oct 27, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

The secondary ground is 'connected' to the case so the secondary (High voltage) only requires one connection. The primary is not connected to the case otherwise the dizzy would not be able to make and break connection.

blue

· #8 · Oct 27, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

3 external connections

LV connectiosn are: + & - on primary
HV connections are: + on secondary

LV- and HV- are connected internally

I don't think the case is connected to the -neg terminal otherwise it would sink the primary all the time and prevent energizing of the primary by the switched ground?

I think Reversing the primary LV connections will reverse spark direction as current will flow in reverse direction on the primary

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2slo4u

· #9 · Oct 28, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

Bingo.

Him

· #10 · Oct 28, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

You re right, the secondary is not connected to the case and is not grounded. Should have hit me sooner since the coil on my car has a plastic case so it definately is not grounded.

And as you said if the dizzy did not also disconnect the secondary the charging voltage would be disrupted.

Post Edited (Oct 27, 7:18pm)

chevyman

· #11 · Oct 28, 2004

Play Golf....??

Whether lightening strikes you (down) from sky..............or

eminates from the ground - (up) through you - to the sky,

....erosion takes place at the point of the spark / terminus - - - - -

- - - your head in either case...........

i.e., the weaker plug surface, (in metal compound here) or the hottest, erodes first.

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chevyman

· #12 · Oct 28, 2004

(puts head in hands here)......

Stated........."I think Reversing the primary LV connections will reverse spark direction as current will flow in reverse direction on the primary"

I hope you're gonna be up all night thinking about that one........?

(picture thinking out loud here).........Hmmm...lemmmesee, the secondary is charged with a 20,000 volt potential, and it's going to reverse.......no, err....well, if I hold my finger in front of the coil wire ..........err..no....wait....

steves280

· #13 · Oct 28, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

http://www.mgcars.org.uk/midgetspriteclub/sprite/spriteposneg.htm

Just one link I found, it does reduce the avalible spark energy and can cause a marginal system (read old points or transistor ignitions) to misfire.
-----------

Whilst the coil will work when connected the wrong way round its effective output voltage can be reduced by up to 40% so weakening the spark . Additionally if the LT side of the coil is reversed then the HT Polarity is also reversed so the electrical pulse and hence the spark at the plug travels in the opposite direction to the normal (normal direction for the spark is from the center electrode to the spark plug arm).

Electrons leave a hot surface better than a cooler one, and in service the arm of the spark plug is more efficient at dissipating heat than the central electrode. Therefore running the system in reverse will give a weak spark for this reason in addition to the reduced HT voltage.

If the spark is travelling the wrong way you will also get above average erosion on the spark plug arm as the greatest erosion happens at the electrode from which the spark leaves. The central electrodes of spark plugs are specially designed to help compensate for this but obviously the arm is not. Above average increases in the spark plug gap can indicate that the system is operating in reverse and obviously incorrect spark plug gaps will again lead to a weaker spark.

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jcool78 2plus2

· #14 · Oct 28, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

Ooo...head hurting...information overload...ooo...

2.4T

Discussion Starter · #15 · Oct 28, 2004

Re: .......So I says: My coils hooked up backward! Then he said.

The haynes says the black/white wire is 12+ and the black is the -. I took the leads off the coil before testing. O-ya-the haynes also says hooking up the coil backwards causes up to a 60% loss in spark efficiency.

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