Hi, I am trying to replace the batteries on a wall mounted underfloor automatic thermostat. How do i remove the cover without breaking it

Some electro-mechanical thermostats invariably click as they operate and if secured to something hollow, like a stud wall, the noise will be magnified.
There are virtually silent electro-mechanical types usually using a mercury switch and it is reasonable to assume electronic thermostats will be silent.

Hi Hongyi Yu,
Your thermostat consists of two parts: the thermostat cover and the base. To remove the cover, pull it straight out from the base. To replace the cover, line up the cover with the base and press until the cover snaps onto the base.

Monica, There might be a break in the wire mat, you or a electrician will have to check with a digi multi meter.
Links below show how.
"I hope this helped you out, if so let me know by pressing the helpful button. Check out some of my other posts if you need more tips and info."

How to test underfloor heating with multi meter

How do test the resistance of my electric underfloor heating system

http://www.suntouch.com/support/troubleshooting

Testing underfloor heating

Look for a stuck relay that controls the pump

The outer shell of the thermostat pushes on(clips) to mounting bracket attached to wall.

1. Remove the packing material from the thermostat. Gently

pull the cover straight off the base. Forcing or prying on

the thermostat will cause damage to the unit

http://www.emersonclimate.com/Documents/White-Rodgers/0037-6488.pdf
This is the manual for your unit.

Please switch off power.
1.Remove cover from old Thermostat. If it it doesn't snap off when firmly pulled from the bottom,check for a screw that locks cover on.
2 Loosen screws holding thermostat sub-base wall plate or wall and lift away.

Many of the newer Honeywell models have a battery compartment that can be accessed without removing the thermostat.
Look for a small tab at one of the top corners of the thermostat. If this is not the case try pulling directly away from the wall at the bottom, then tilt up.

Removal & Installation 3.9L, 5.2L & 5.9L Engines To Remove:

1. Before servicing the vehicle, refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • Negative battery cable
   • Coolant until level is below thermostat
     
     
   • Support bracket located near rear of alternator (A/C Vehicles)
     
     
   • Alternator drive belt by attaching a wrench to the pulley mounting bolt of the automatic tensioner, rotating the tensioner clockwise to release belt tension, and removing the belt:
   • Alternator mounting bolts, but do not remove any wiring at alternator
   • 4WD indicator lamp wiring harness (4WD vehicles)
   • Alternator and position aside WARNING
     When servicing constant tension hose clamps, use only tools designed for servicing this type of clamp, such as special clamp tool (number 6094). Always wear safety glasses when servicing constant tension clamps. Always replace constant tension clamps with the same numbered clamp.
     
   • Radiator hose clamp and upper radiator hose at thermostat housing and position wiring harness aside to gain access to thermostat
     
     
   • Thermostat housing mounting bolts, thermostat housing, gasket and thermostat

To Install:

1. Clean intake manifold and thermostat housing mating surfaces.
2. Install or connect the following:
   • Thermostat (spring side down) into recessed machined groove on intake manifold
   • Gasket on intake manifold and over thermostat
     
     
   • Thermostat housing to intake manifold NOTE: The word FRONT is stamped on housing and must be placed towards front of vehicle.
     
   • Housing-to-intake manifold bolts.
     1. Torque to: 200 inch lbs. (23 Nm)
   • Upper radiator hose to thermostat housing
     
     
   • Alternator (A/C Vehicles)
     1. Torque to: 30 ft. lbs. (41 Nm)
   • Support bracket
     1. Torque to: 40 ft. lbs. (54 Nm)
   • Drive belt over all pulleys except idler pulley
   • Socket/wrench to pulley mounting bolt of automatic tensioner and rotate clockwise
   • Belt over idler pulley, let tensioner rotate back into place and remove wrench
   • Coolant
   • Negative battery cable
3. Start and warm the engine and check for leaks.

4.7L Engine To Remove:

1. Before servicing the vehicle, refer to the precautions at the beginning of this section.
2. Remove or disconnect the following:
   • Negative battery cable
   • Coolant
3. Safely raise and support the vehicle.
4. Remove or disconnect the following:
   • Splash shield
   • Lower radiator hose clamp and lower radiator hose at thermostat housing 4.7L engine shown 3.7L similar
     
     
   • Thermostat housing mounting bolts, thermostat housing and thermostat

To Install:

1. Clean timing chain cover and thermostat housing mating surfaces.
2. Install or connect the following:
   • Thermostat (spring side down) into recessed machined groove on timing chain cover
   • Thermostat housing on timing chain cover
   • Housing-to-timing chain cover bolts.
     1. Torque to: 112 inch lbs. (13 Nm)
   • Lower radiator hose on thermostat housing
   • Splash shield
3. Lower vehicle.
4. Fill cooling system.
5. Connect negative battery cable to battery.
6. Start the engine and check for leaks.

There is a seam around the edge of the Thermostat , a small screwdriver or butter knife should do the trick , if not then its mounted to a plate on the wall that has 4 corners basically...Gently squeeze the bottom and pull the bottom out , they are pretty sturdy and you shouldn't have a problem,...the wall plate may flex a little while doing this