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MSC4000 - MSC15000 USER GUIDE
a) You need to first check the coil of the liquid line valve to ensure that it is functioning.
The easiest way to verify if the coil is energized is to take a screwdriver and touch it to
the screw or post on the top of the coil. If the coil is energized there will be a magnetic
field pulling the metal to the screw or post. If the Power Saver Active light is off and
there is no magnetic pull; the coil is not functioning.
b) If you have determined the coil is not functioning there are two things you must check.
- Test the coil electrically for continuity to ensure it is not shorted. If it is shorted replace
the coil
- If the coil is not shorted you need to check the K2 relay marked “Suction”, terminals 7
and 8. There should be a 120V output from this relay. If there is not replace the board.
c) If the coil is functioning and the restriction seems to remain the valve may be the
problem. The internals or the whole valve should be replaced. Or the restriction could
be in the expansion valve. This is rare but possible.
Remember all of this must be checked while the unit is operative and in the refrigerating
state. The way this is determined is by the Power Saver Active light being off.
2. Service valve.
When the dryer is fully operative, all refrigeration service valves with the
exception of the service valve on the bottom of the evaporator on models 330’s and up,
should be open. If one should be closed, even partially, this could cause enough of a
restriction to cause low-pressure problems.
3. Faulty expansion valve.
This is a very rare situation however there is means of testing
this theory. Test by applying heat (hair dryer) to TXV sensing bulb located just after the
flood level control for about 30-45 seconds. This should cause the unit to flood back
and lower the super heat. To check this, take a temperature reading on the suction
accumulator, it should be extremely cold, if it is not, your expansion valve is stuck closed
or is dirty. Check to make sure that the capillary tube from the power head to the sensing
bulb is not severed; this could cause the valve to close. Your suction accumulator
normally shows a level based on temperature of being 1/3 to 1/2 full. If it is less you may
have restriction.
E. Disconnected or Faulty Jumper Wire (Very rare)
There is a violet jumper wire that runs from the outgoing current on the low-pressure switch to
terminal 18 on the main dew point controller. This terminal must see power at all times in order
for the unit to function. If the low-pressure switch opens it severs power to terminal 18 and
the unit shuts down on “E6”, however, if the jumper wire is faulty or disconnected terminal 18
does not see power and will shut down on a false “E6”. To check remove power from the unit
and check for continuity through the jumper wire if there is none inspect and/or replace wire.
Reapply power. If the unit still shows “E6” and the low-pressure switch has checked good, the
problem is in the board.
9.7
Diagnostic Code “E7” Shutdown on High Head PSI
If the discharge or “head” pressure of the dryer refrigeration unit exceeds 350 psi g (24.13 bar g)
it breaks contact through the high-pressure switch. This in turn breaks power to the refrigerant
compressor shutting it down for protection.
To correct this:
1. Bypass the compressed air around the dryer. 2. Based on the size of the
unit you will have either manually resetting pressure switches or a reset through the control panel
by pressing the mode selection button off then on again after 10 seconds. If the condition is not
corrected you may have to repeat this step. If it continues after that, check the following probable
causes:
A) Dryer Overload
This causes the freon to evaporate gas faster than the compressor can remove it, thus raising
the suction and head pressures and the compressor discharge temperature. Probable causes
are:
