No Power to Heatbed on RAMPS

Building a RepRapGuru from a kit received at Christmas. The heat bed is not heating. Voltmeter on D9 terminals shows 0 after manually switching on the heat bed in Repetier. Guidance on where to go next with troubleshooting would be appreciated.

Did you wire the powersupply to all four connector of the green plug?

The heated bed is usually connected to D8!
D9 is for a cooling fan, D10 for the extruder.

I was mistaken, heated bed is connected to D8. Four wires from power supply go to the green plug. Both pairs run 11.9v from the Power Supply to the green plug and are in the same order (red black, red black) as on Step 42 in the build manual.

Does the controller see a heated bed temperature. It will not try to heat up the bed if if can't see some sort of a bed temperature. Safety feature.

Repetier doesn't show a temperature for heated bed. Heated bed wires are connected to T1. It is oriented with the black wire towards T2 and the red wire towards T0.

When not heating the extruder and bed should both show ambient temperature. If they are not doing this then you probably have a thermistor connection problem.

Thermistor on extruder works fine. Verified the RAMPS board is okay by temporarily plugging extruder thermistor into T1 then powering up. Repetier showed ambient temp for "heated bed". Verified continuity of heated bed thermistor wires (solder point on heated bed to plug that goes onto the RAMPS). Soldered connections on heated bed look fine. Problem seems to be narrowed down to thermistor on heated bed. Are there additional troubleshooting steps that can be done? Next steps?

Is this a bead type thermister that is taped to the underside of the bed, or is it a chip type that is soldered to bed contacts ?

You have set the temperature sensor type in your configuration.h ?

ie
#define TEMP_SENSOR_BED

is set to something other than 0?

Q1
It must be a chip type thermistor as the wires are soldered directly to the bed and I don't see anything taped to the heated bed. It is attached to P2 on the heated bed.

Q2
From the config.h file...
#define TEMP_SENSOR_BED 6 <== should I set this to 0 (zero) then push it to the Arduino?

When I first got my Anet A8 I got a thermistor failure showing for the bed. I went over and over the wiring to no result until eventually (I should have thought of it sooner) I checked the thermistor resistance at its connection on the bed edge and got open circuit. Reading directly across the thermistor itself gave the required 100k. I then took readings from the bed edge connections to the thermistor and found that one of the extremely fine print tracks read open circuit. Examination of the track with a powerfull magnifying glass showed up a hairline thickness break in the track. A manufacturing fault since it was covered with the varnish coating.