What I know so far is -
1) front washers and wipers work
2) rear wiper works
3) there is one washer pump on this MY and services both front and back. One internet post says that ford changes the polarity of the motor in the pump to service front and back separately without using two pumps. Could not verify this contention.
3) motor pump noise when the front washers are engaged.
4) no motor pump noise when the rear washer is engaged
5) plenty of fluid in single reservoir that service front and back
6) line to back could be frozen but pump is not engaging anyway
7) rear nozzle has been checked. I can blow air through it so not clogged.
7) there is one relay that controls multiple things including rear wash logic so it may be "partially" faulty
8) since front washer works, I don't think it's a fuse issue
9) i personally think its a faulty multi-function switch that controls front and rear washer and the four way flashers.

Any opinions, conjecture, theories or related experiences welcome.......

 

The pump has two connectors, one to the front wiper, one to the rear. You can reach it by pulling the bumper cover off the passenger side or by removing the wheel and the splashing guards. once you get to the pump, you can switch the hoses then turn on the front wiper to test the rear wiper. if no water comes out, then you got a hose issue.

 

Thanks. I will follow that tip up once I get up the gumption to work in the freezing cold.. We were actually in there to see if the bottle, pump, lines or grommet were leaking a couple of months.which it was not. I didn't know at the time that the washer wasn't working so we put everything back.

 

Follow-up. Replaced the washer pump to no avail. I suspect the rear wiper assy is a cheap "white box" without the intelligence to foward the signal to wash from the steering wheel stalk control.

 

This may help diagnose: It's from the 2011 Workshop Manual but interesting because of the GROUNDS. We know over the past 11 years or more that water ingress past the rear glass hatch weather stripping that allows water to drip down the inside of the back glass can lead to ground faults and corrosion, not limited to the rear wiper motor but also rotting out of the rear hatch bottom.So it appears that the REAR WIPER MOTOR has an INTEGRAL RELAY!

If your rear glass hatch weather stripping is allowing water ingress past the seal and down the inside of the rear hatch glass, one of the symptoms is bad grounds back there, an inoperative rear washer, and of course rotting out the bottom of the hatchback.

Other troubleshooting tips:

 

I suspect that maybe you've got a bad ground path in the rear WIPER motor assembly (which they say contains its OWN INTEGRAL RELAY) and could be stopping the washer back there.