In my 2006 Chrysler 300 there is a fuse box in the engine compartment and one in the trunk next to the spare tire. Engine fuse box seems to be more "engine" related electrical whereas trunk fuse box is more interior electrical
The automotive thermostat is a temperature controlled on and off valve.
When the temperature rises to a predetermined temperature, the
thermostat opens up to allow the engine coolant to flow through the
cylinder block and the radiator. This flow is crucial to maintain
optimum operating temperature for fuel efficiency, enhanced
driveability, and engine protection. The coolant flow is reduced when
the engine is cold, and the flow is increased when the engine is hot.
Contrary to popular opinion, operating the vehicle without the
thermostat doesn't make the engine run cooler. It will actually run
hotter because there isn't a thermostat to slow the coolant flow. This
means the coolant doesn't stay in the radiator long enough to dissipate
TO TEST THERMOSTAT
There are several ways to test the opening temperature of a thermostat.
One method does not require that the thermostat be removed from the engine.
Remove the radiator pressure cap from a cool radiator and insert a thermometer into the coolant.
Start the engine and let it warm up. Watch the thermometer and the surface of the coolant.
When the coolant begins to flow, this indicates the thermostat has started to open.
The reading on the thermometer indicates the opening temperature of the thermostat.
If the engine is cold and coolant circulates, this indicates the thermostat is stuck open and must be replaced.
The other way to test a thermostat is to remove it.
Suspend the thermostat completely submerged in a small container of water so it does not touch the bottom.
Place a thermometer in the water so it does not touch the container and only measures water temperature.
Heat the water.
When the thermostat valve barely begins to open, read the
thermometer. This is the opening temperature of this particular
If the valve stays open after the thermostat is removed from the water, the thermostat is defective and must be replaced.
Several types of commercial testers are available. When using such a tester, be sure to follow the manufacturer's instructions.
Markings on the thermostat normally indicate which end should face
toward the radiator. Regardless of the markings, the sensored end must
always be installed toward the engine.
When replacing the thermostat, also replace the gasket that seals
the thermostat in place and is positioned between the water outlet
casting and the engine block.
Positioning a thermostat into an engine.
Generally, these gaskets are made of a composition fiber material
and are die-cut to match the thermostat opening and mounting bolt
configuration of the water outlet.
Thermostat gaskets generally come with or without an adhesive
backing. The adhesive backing of gaskets holds the thermostat securely
centered in the mounting flange, leaving both hands of the technician
free to align and bolt the thermostat securely in place.
TO REPLACE THERMOSTAT
CAUTION If the radiator is filled to the
top with coolant and the engine is run without the radiator cap in
place, the coolant will expand and spill over as the engine warms up.
Drain some coolant into a clean container until the coolant level is below the thermostat housing.
Remove the upper radiator hose connection from the thermostat housing.
Loosen the housing bolts and remove the housing.
Remove the gasket and scrape it carefully from the surface of the
housing and the mounting surface on the engine. If the gasket remains
on either of the surfaces, there will probably bea coolant leak after
reassembly. Some engines use a rubber O-ring to seal a thermostat
Compare the size of the thermostat to the old one. They are of different sizes, types, and temperature ratings.
The temperature rating is stamped on the sensing bulb on the bottom of the thermostat. The temperature bulb faces the block.
When replacing a thermostat, be sure that the thermostat fits into
the groove in the block or outlet housing. If the thermostat is
installed upside down, the engine will overheat.
Install the gasket.
Reinstall the thermostat housing. Refill the system and run the engine or pressure test to check for leaks.
When the engine has reached operating temperature make sure the thermostat opens.
You should be able to see coolant circulating within the radiator.
Another way of checking thermostat operation is to feel the top of
the radiator hose or use a thermometer or multimeter with a temperature
probe to confirm that the coolant is warming up.
If the engine is overheating, but the top hose is still cool to the touch, the thermostat is stuck closed and must be replaced.
When a paper gasket is used and the recess is in
the thermostat housing, it is a good practice to position the
thermostat into the recess and glue the gasket to hold it in place. If
it falls out of its groove during installation, the outlet housing can
be cracked or a coolant leak will result. Before tightening the water
outlet housing, try to rock it back and forth to be sure it is flush.
Housings are often cracked during this step.
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