What replacement can I use on my 2005 Ford Five Hundred Rear Coil Spring can not get the originals they have discontinued them.

2005-2007 Ford Five Hundred Speed Sensor - JC Whitney

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Shop for a 2005-2007 Ford Five Hundred OE Replacement Vehicle Speed Sensor by Motorcraft with a 30-day Satisfaction Guarantee at JC Whitney, America's ... images for 2005 Ford Five Hundred Where is the ...

Jack up the car, put it on jack stands and then slide under it.

here in California a spring shop can make them for you from a sample spring. Sacramento area

I would be taking this to a suspension specialist for good after market springs of the right length. The struts used may be too short in travel and that is what is holding the rear down or it may be just weak springs

According to the book, the relay is incorporated into the smart junction box. There may not be an actual relay you can replace.

You have a shop with no data base such
as Alldata,Mitchell or Identifix !!

Automobiles: 2006-2007 Ford Five Hundred 2WD & AWD, Montego

If the steering is getting a little hard to turn at low speeds, this would indicate a loss of Power Steering, and the steering is reverting to "Non-Power" steering, just like the days of the Ford Model T or Model A. Loss of power steering is usually caused by low level of PSF (Power Steering Fluid).
So first on my checklist would be checking the PSF level in the reservoir.
Also bleed (air) from PS (Power Steering) pump.

The Ford Five Hundred has front MacPherson struts, so check these for leakage (of the dampening fluid in the strut cylinder), or breakage of their coil springs.
These springs can actually weaken over time, but this is impossible to see - you must "feel" it by bouncing the strut up & down - preferably with your hands on the top of the strut tower in the engine compartment (rather than on the exterior finish).
If the MacPherson struts have weak/broken springs, these components are not separately serviceable, and the strut would have to be replaced as a unit (and preferably both left/right to maintain smooth/even ride).

The Five Hundred also has rear shock absorbers with springs - check for leaks/breakage/weakness here too.

Steering losing responsiveness/wander - checklist
Priority Action Part Type Cause
1 Inspect Rack & Pinion - Center Wear From Internal Fluid Leaking Around The Rack Piston.
2 Inspect Steering Stabilizer Bracket - Loose or Broken Steering Stabilizer Bracket.
3 Inspect Front Lower Control Arm - Front Lower Control Arm loose/missing bolt(s)
4 Inspect Front Lower Ball Joints - Front Lower Ball Joint(s) Worn/Loose
5 Inspect Front Upper Ball Joints -Front Upper Ball Joint(s) Worn/Loose
6 Inspect Tire Pressure - Tire Pressure should be 35 PSI for the Five Hundred and Montego's P225/55R18 OEM (Original Equipment Manufacturer) tires.

Harsh ride - checklist

1 Inspect Rear Shock/Strut - Shocks/Strut failing/leaking.
2 Inspect Front Shock/Strut - Shocks/Strut failing/leaking.
3 Inspect Coil Spring - Incorrect Coil Spring Selection or Installation.
4 Inspect Coil Spring - Coil Spring broken.

They are stand alone shocks
Here are the part numbers you need.
MOTORCRAFT Part # AST236 Rear Left
MOTORCRAFT Part # AST235 Rear Right
About $100.00 for both parts.

from inside the trunk there is a removable access panel for both sides, left and right.

The lights have 2 light bulbs in it, you probably have to replace one