No spark at coil.

Hi everyone,

New to your forum, & the 75 Dart SE I just bought for my son.

I drove this car 2 hours home on Friday, & around the neighborhood Friday & Saturday with no problems. My intentions were to go through everything before I made this my sons daily driver. However on Saturday after my boys & I finished doing our first round of cleaning the car up it wouldn't start. After further inspection there was no spark at the coil. So here are some of the facts that I have found.

-Dual Ballast resistor was new but installed upside down.-Corrected
-ECU was a 4 pin, Harness is a 5 pin. I had a 5 pin that came with the car so I switched it out.
-I did OHMS test on all the harness lines & everything checked out.

This is where my question lies
-+side of Coil shows within 1 Volt of Battery not connected to the coil however when connected to the coil the voltage drops to around 3.5 Volts.

Any thoughts. & at some point I think I will upgrade the electronics.