power shortage at coil

[christianlarsen]

I have the problem that i only have about 4 volts at the coil+ when ignition is on.
I have a ballast resistor, blaster 2 coil and unilite mechanical/optical dizzy.
The dissy red is connected to coil+, not the 12v side of the ballast resistor (i have seen mallory diagram that shows it should sit there, but this has worked for yrs...)
I have tried to swop the optical thing of the dizzy with no change.
When I take of the dizzy red at the coil+, I get 11.5 volts at the coil+ (with ignition on), so i thought that it was the optical part of dizzy or a shortage/bad wire between the the coil and the dizzy. Im pretty sure all 3 wires in the dizzy (red/green/brown) have solid connections, f.x. I read 11.5volts when i test the brown/ground with battery+ and also the green (coil-) reads 11.5 volts when tested with battery+ (both situations with ignition off).
Im running out of ideas and need help/hints to what could cause this.

PS: I have a tach connected to coil- but did tests without that connected and still only 4 volts....

[christianlarsen]

hmm I noticed there is some white paste/grease at the back of the optical module (605) where it touches the dizzy. Anybody knows the purpose of that
If I unscrew the module I get 11.5 V no problem, so it looks like a short between the optical module and the dizzy itself. Im thinking maybe that white paste is there to avoid shortage, but it seems a little flaky ??

[mhinders]

In the electronics world it's common to use a white paste/grease behind hot components to improve the heat dissipation into a heatsink for example. Sounds like this might be the case with your stuff as well, i.e. leave it there.

I would start with the simple stuff, 4 volts at the coil is too low. Your ballast resistor might be stealing too much voltage from the coil. Try with a ballast resistor that has a lower resistance.

A higher performance coil usually has lower resistance than a standard coil. This means that you have to replace the ballast resistor with one having a smaller resistance value, to get the full output from the new coil.

If you have an ignition module that has a built in current limiting feature, you don't need a ballast resistor at all.

[christianlarsen]

Ah you must be right about the head dissipation (can recognize it now from a cpu....silly me :-) )

Im using pretty standard stuff: A Unilite dizzy for a 440 (http://www.summitracing.com/parts/maa-3757801) with the suggested ballast resistor (http://www.summitracing.com/parts/maa-700).

I have tried with the old "no-name" ignition coil that was on the car when i got it , and now with a brand new blaster II coil.

I also tried to switch out the optical module in the dizzy.

Any combo gives me 4 volts. If I remove the red wire from the dizzy connected to the coil+ I read 11.5 volts between the coil+ and battery-. If i unscrew the optical module so it does not touch the dizzy (leave it hanging in "the air") i read 11.5 volts instead of the 4 volts at coil+ (with optical module connected again...). That is why im thinking there is a shortage between the module and the dizzy

[christianlarsen]

Ok I put the module in the dizzy again and now I can read 11.5 Volts instead of 4....Must be a short somewhere around the dizzy I haven't found.
I really suck at this

[mhinders]

I wouldn't assume any short circuit at this time, that would most likely smoke something.

Your Blaster 2 coil is supposed to have a ballast resistor of 0.8 Ohms. The ballast resistor you are using is 0.75-1.5 Ohms. It's the correct value (0.75 Ohms) only when starting in cold weather, once warm, or already in warm weather,  it allows too little current to your high performance coil. It might still work, but you aren't using the full capabilities of the Blaster 2 coil.

The red wire from distributor is not supposed to go the + side of the coil in your case, it's supposed to go to the full 12V supply you (should) find in one end of the ballast resistor (coming from the ignition switch "on").

Good luck!
Martin