I tested it while it was running and was getting 27v on the main red and 14 or 15 to the pink/black wire. Is this correct?
On a stock system the red wire is hooked to the 24v Postive Terminal Board via the BIG resistor pack on the firewall. So 27v with it running is okay.
The pink/black wire is being fed from the 12v ignition switch. Running it will show 14-15v with the key on. Of course its on...the trucks running...LOL
Sounds like everything is wired correctly, now to test the other wires in the circuit before you install the new controller card. It is covered in Paragraph 15, Page 2-62 of the TM 9-2320-289-20.
You will need a ohm/voltmeter and use the chassis ground.
What you will be checking is the:
Purple/white wire #930a - It will show 12v when the key is in the
START position. This energizes the controller during starting
Light Blue wire #505 - Jumper this wire to ground with the key in the
RUN position. You should hear the relay on the firewall click.
Dark Blue wire #507 - Jumper this wire to ground with the key in the
RUN position. You should see the wait light come on. If not, check the bulb
Pink/Black wire #39G - It will show 12v when the key is in the
RUN position. This is the power feed for the controller when the key is on. (You have already checked it so it is good)
Orange wire #503a - This is the small orange wire. Jumper the LT BLUE wire to ground with the key in the
RUN position. You should hear the relay on the firewall click. And you should also show 24v on the orange wire (It will drop to 12v if all the glowplugs are working correctly)
Yellow wire #151b - This is the wire for the tempature sensor on the block. With the key
OFF, check for ~800 ohm with the engine cold. When the engine is hot, the resistance will increase and keep the circuit open, not allowing the controller to turn on the plugs.
Black wire #151a - With the key
OFF, you should have 0 ohms. This is the ground for the controller and is connected to the Negative Terminal Block.
Pink/Black and Lt Blue wires at the GP Relay on the firewall - with the key
OFF, check the reistance between the two small terminals. You should have 6-10 ohms. Anything highre than that indicates the relay might be bad and needs to be replaced.
After you check all these circuits, you can "safely" install your new controller card without fear of frying it.