Voltage Drop 12V to 6V?

[DrMPH]

Hello, I have a 1982 Alfa Spider that I have been charged with finishing the MS2 V3.57 2.88 install. I didnt start the conversion, I just have enviable task of finishing it.
My problem is the main 12V power source. I have 12V at the DB37 pin 28 when the MS is not plugged in, at the moment there is an exposed solder connection from the main relay to the DB37 and the connection also has 12V when the MS is not plugged in.
I suppose I should add that the DB37 cable is soldered into the pins on the stock L-Jet ECU plug so that the factory harness could be used (I dont think this is such a great idea, at least in execution)
SO...I have a relay, a fusible link, a ECU-DB37 "interface" and the plug on the end of the DB37.
When I install the MS to the DB37, the voltage drops to 6V at the MS, and at the ECU-BD37 interface, while it remains 12V at the fusible link and the relay.

With the MS unplugged, the voltages are as follows
12V every where.

With the MS plugged in:
12V at relay
12V at fusible link(both sides)
6V at ECU-DB37 interface(measured at the currently exposed Pins)
6V at PIN28 on DB37, also seen at Battery Voltage Gauge in Megatune.

I had thought that a high resistance in the DB37-ECU interface would be a likely culprit, but my Ohm-meter barely registers.
Likewise, if the DB-MS end plug was fouled, I would see 6V at PIN28 with or with out the MS installed.
Furthermore, with the stim installed directly to the MS (no cable, straight plug to plug) the voltage is correct. What I feed the stim is what the MS sees.
The battery voltage gauge in Megatune is working, as the external (relay, link, interface) voltages are equal to what the gauge reads.

I need to get past this so I can move on, and I have tried disconnecting every sensor, checking grounds. I am probably missing something obvious, so feel free to point this out to me.

Thanks

[Matt Cramer]

Does the MS have any voltage drop problems on a Stimulator?

[john.p.clegg]

Basic theory says that you have either a big load on the voltage when connected to cause the drop....OR..... you have a high resistance somewhere in line to cause the voltage drop when connected....

P.S. with no load connected you will see a good 12 volts even through a high resistance "fault"

John

[DrMPH]

No, there is no drop on the Stim, and I have Ohm-ed out the wires and connections in the car, and it shows no resistance. No more than .01 Ohm.

[Matt Cramer]

Check to be sure the TPS VREF isn't shorted to ground.