So, my car only will run if the condenser wire is on the positive side of the coil. Which is weird, because everything I see says it's supposed to be attached to the negative side of the coil.

Anyone have an idea of why this would be happening?

Are you running points or Pertronix / other electronic ignitions?

Sounds like you have a flaky condensor that may be leaking current. A condensor is nothing more than another name used in automotive for a capacitor.

Since a capacitor doesn't flow Direct Current, from a current flow standpoint, it should not matter which side you attach it to. However, on the positive side of the coil, it does next to nothing to protect the points from arching and burning up.

Measure across the condensor with a DMM. Should read as infinite resistance. Anything less is no good.

If your DMM has a capacitive measurement, measure the capacitance. It should measure something on the order of 0.2 micro farads (uF) or 200 nano farads. (nF) If it won't measure a capacitance, it is bad.

If you have an analog multi-meter we can go a step further but at this point most people only have DMM's so I'll assume you don't.

Are you sure? I've hooked it up backwards before and it smoked the green wire.
Melted the plastic insulation right off the condenser wire in seconds.

@coronamike maybe you can share a picture of your current set up of the showing dizzy (remove cap) along with the coil that can show clearly the wirings. For sure members can easily give you idea.

Having a condenser on the positive side of the ignition will not do much. It may suppress some RFI when listening to some channels on the AM radio, but having a condenser on the negative side of the coil would do a better job of suppressing noise while also protecting your points.
Do you have points or is it a pointless ignition module? If you have the module, then you won't need anything. You can keep the condenser on the positive side of the coil, but again, it's not doing a whole lot.

I DO have points - I actually DID fry a condenser wire when I was trying to figure this out - but it was on the Negative side when it happened.

The car just won't even start if the wire is on the negative side of the coil. But it will start right up as soon as I move it over.

I'll try to post a pic in a bit. Thanks

Positively sure that DC current won't flow though a capacitor.


However, I could see your situation happening. The green wire is shared with the black wire off the condensor. If the points were closed (grounded) and you hook the green wire to positive, you would have a direct short to ground though the green wire, to the points to ground. Poof!

Thank you for pointing that out. I was thinking of the condensor only and not accounting for the shared connection inside the distributor between the condensor green wire and a potential short to ground if the engine stops with points closed. I'm ashamed of myself.

Good catch. @Mark Henry

Need OP to post picture of the condensor he's dealing with.

@CoronaMike

Please check that + side of coil is correctly wired. Schematic shows Black with red tracer is postive (73' schematic) - belive same all years.

Is it possible that you've mistaken that black with red trace as coil negative?

Here's the picture -

So the + (15) side has the condenser (the wire is red instead of green), the black wire and the yellow wire.

The - side has just the 'double' wire.

Click to view attachment

Ok that's ass backwards...I bet the coil is fried.

the picture is kinda upside down - the positive side is on the right. the only thing on the wrong side (I believe) is the condenser.

the coil tests ok.

What color is the wire behind the red? black/purple? yeah I forget Ljet, just don't remember the double black.

I've never seen a red wire for a stock condenser. If you're running points, coil, condenser cap, rotor, it all has to be Bosch.

Yeah - it's the black/purple wire. The condenser is from autozone. The first green wire one I got from O'reiley's melted (on the negative side). :/

I'm with Mark. Backwards

And to many wires.

Positive side (terminal 15) is one wire -- shold be black with red trace (12v +) both from schematic and from the recent post that Clay did on the relay board. Looks to me like you may have some splices / non OEM colors in there (no yellow wires go to coil for a 74')) in the schematic for a 74'

Click to view attachment

Black with purple tracer is the Tach signal -- That belongs on coil negative

Condennsor - typically green on Bosch condenser -- belongs on coil negative.

Total of 3 wires involved. Not sure what else is being tapped off your coil.

Here's the good news. Technically the coil doesn't care if it's wired backwards. There is a primary coil which is what all these connections go to and a secondary high tension ouptut to the distributor cap.

That's why it runs.

If it were me I'd want to wire it properly, would want to get proper color coded wires in there, and would figure out what the extra wires are.

You have a Ljet? That white wire needs to be on the negative terminal, the car will never run if it's not

I don't know squat about L-jet. What is the white wire? Is that white wire what @CoronaMike was calling the yellow wire?

Assuming that it does belong on the coil negative side for L-jet, that brings the total of wires involved to 4.

Still one to many wires on your coil - something else tapped off the postive feed - which is actually the negative side of your coil?

The white wire may have faded to a yellowish color, hard to see. Anyways, if it is a Ljet 914 and not carbureted, that wire will be needed and really needs to be on the negative side of the coil for car to run.

This wire feeds pin one to the Ljet ECU. The ECU processes the ignition signal to set up the batch firing for the fuel injectors.

If this was my car, I would check the integrity of this wire by checking the resistance at pin 1 of the ECU connector to the end of the wire (at the terminal). You should have 0 ohms. I doubt any damage has been done, but better safe than sorry.

I think from original post #1 his car is running as wired so I don't belive any damage has been done based on that description.

The bottom line is that primary side of the coil has been wired backwards but the coil itself could care less. It is just a simple transformer and really doesn't care which direction current flow though it.

At a minimum, all wiring should be swapped over to proper terminals to avoid future confusion.

I'd still want to know what the other "double" wire is. one of them is clearly the 12v + feed but what is the other?

Not uncommon for someone to tap off the coil but it really shouldn't be done. Usually causes no harm but the high voltage spikes that can be induced into the coil primary if the condensor goes bad usually aren't good for other components.

Ok - so yeah - You guys were right - I DID somehow end up getting it turned around.

I just tested the coil and it's still getting just under 12 volts (11.67) - so, I'm hoping it's still ok.

It still ran when I started it up - but I had been in the process of resetting the timing, etc - so it's idling verrry low - so, I'll have to figure out what's going on now.