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Mercedes-Benz Tech Tip: A/C Compressor Clutch Won't Engage
Problem:
A/C compressor clutch doesn’t engage; EC light on the climate control
push-button panel is continuously lit.
Affected Vehicle: 1997 Mercedes-Benz
E320 3.2L.
Service Procedure:
1. Read and clear DTCs in the A/C control module using a push-button on-board
procedure. Turn the key to the ignition “ON” position.
2. Set the left temperature selector on “HI” and the right temperature selector
on “LO.”
3. Within 10 seconds, press and hold the “REST” and “EC” buttons simultaneously
for six seconds, then release.
4. The Light Emitting Diode (LED) in the recirculation button should begin to
blink. The display should read “di A.”
5. Press the right “Auto” button to display DTCs. Keep scrolling through the
list by pressing the right “Auto” button until the display shows “E FF.”
6. To erase DTCs, press and hold both “Auto” buttons simultaneously for three
seconds and release. The display should show “D FF.” Switch off the ignition.
7. Restart the engine. If the “EC” button lamp is illuminated, press and release
the “EC” button. The lamp should go out. If not, recheck for DTCs Key On Engine
Off (KOEO), then recheck compressor operation.
Courtesy of IDENTIFIX.
AutoA/C Repairs Home
Some of the 1994 Saturn owners may have experienced an annoying
air conditioning (A/C) problem. their A/C stopped blowing cold air. And the
strange thing was, when driving around town, the A/C worked fine.
This problem still plagues 1994 and newer Saturn models, equipped with an R-134a
air conditioning system. The core of the problem is an A/C compressor suction
set point that could be too low for some customers' usage and driving patterns.
This condition results in complete evaporator freeze-up after extended periods
of highway driving.
1. The first thing to do is confirm with the customer that their A/C system
functions normally in all conditions except extended driving at highway speeds.
If so, adjust the A/C compressor set point using the following procedure.
NOTE: The engine does not need to be running for the A/C compressor set point
adjustment.
2. Locate the setscrew on the rear head of the A/C compressor.
IMPORTANT NOTE: The setscrew will be covered with either a solid silver label or
a silver label with the words: "CAUTION: BE CAREFUL TO KEEP HANDS CLEAR OF THE
ENGINE COOLING FAN. THE ENGINE COOLING FAN MAY OPERATE UNEXPECTEDLY." If the
silver label has been broken, or an orange replacement label is present, DO NOT
continue with this procedure. Additional adjustment of the setscrew could result
in reduced A/C system performance at higher ambient temperatures.
3. Determine where the large slot in the setscrew is located. (The slot can be
felt through the label with a screwdriver.)
4. Using a utility knife, cut through the label for access to the setscrew (1).
AutoA/C Repairs Home
5. Using a permanent ink marker, make a mark on the A/C compressor to indicate
the current position of the setscrew in relation to the compressor rear head
(2).
6. Using a large blade screwdriver, turn the setscrew 1/4 turn clockwise as
viewed from the rear of the compressor.
WARNING: Do not turn the setscrew on the back of the A/C compressor
counterclockwise. The A/C system is under pressure, and turning the setscrew
counterclockwise could cause the setscrew and/or the hot refrigerant/oil mixture
to be discharged. The refrigerant/oil mixture can cause burns and/or bodily
injury.
CAUTION: Do not turn the setscrew more than 1/4 turn clockwise. Adjusting the
set point changes the pressure at which the A/C compressor goes to minimum
displacement. Increasing the adjustment beyond 1/4 turn clockwise will not make
the system colder and could reduce A/C system performance at higher ambient
temperatures.
7. Start the engine and check that the A/C system is functioning normally.
That's all there is to it. A simple turn of the old A/C compressor set point
adjustment screw, and your customer's A/C is blowing colder.
Written by ALLDATA Technical Editor, Rich
Diegle.
Tips to Keep Your Refrigerant
Recycling Machine in Tip-Top Condition
There’s nothing worse than having customers wanting service and
your refrigerant recycling machine is not operating.The following are
suggestions to keep your recycling machine in tip-top condition and ready to
make money for your shop:
1) Make sure that during every A/C service that the oil is
drained from the recycling machine. This is part of doing the service correctly,
as the removed oil should be measured and that amount added back into the A/C
during the charging procedure.
2) Remove an access panel and do a leak check on the internal
components of the recycling machine. It’s a shame to loose expensive refrigerant
due to an internal leak.
3) Check and replace worn gaskets in hoses and couplers. Small
pieces of gasket material can contaminate the recycling machine as well as the
air conditioner being serviced.
4) Replace filters — both in-line hose filters and the filters
in the recycling machine. Filters should be changed yearly at minimum. Old
filters can slow down the recycling process. Refer to the operation manual for
instructions.
5) Check the pressure in the rear tires and fill as required.
Also check that the rim bolts are all present and tight.
6) Wipe off the exterior of the recycling equipment. Remember
your customer sees your shop equipment and may judge your workmanship based on
how well you maintain your own equipment.
AutoA/C Repairs Home
Updates
June 2006
Diagnostic Information To
Consider Before Replacing an A/C Compressor
A recently completed analysis of air conditioning compressors
in General Motors vehicles that had been replaced for noise, vibration and
insufficient cooling concerns has indicated a high number of “no trouble found”
results. Further studies have shown that the root cause of the customer concerns
that might lead to a compressor replacement was often a state of refrigerant
charge issue or in another area or system of the vehicle.
The A/C system refrigerant charge level, either high or low, has been found to
be a major contributor to unnecessary compressor replacement. The ability of a
refrigerant recycling/recharging tool to recover and measure the weight of the
A/C system refrigerant charge will help the technician make a more accurate
diagnosis of a charge level concern prior to any component replacement.
A thorough visual inspection should always be performed before
any tests or repairs are done. Doing so may find an obvious problem that will
save time and eliminate the need for extensive diagnosis. Some additional items,
as listed below, should be considered before a compressor is replaced for noise,
vibration or insufficient cooling concerns.
• The compressor mounting bolts, brackets or braces may be loose or missing.
• The compressor drive belt may be frayed, loose or misaligned.
• The A/C refrigerant lines may be grounding out on body, chassis or engine
components. This may allow noise and vibration to be transmitted into the
passenger compartment.
• The air flow through the condenser may be insufficient.
– The condenser fins may be bent or filled with debris.
– The space between the condenser and radiator may be filled with leaves or
debris.
– The cooling fans may be inoperative or not performing as designed.
– The installation of aftermarket accessories may alter or restrict the air flow
through the condenser.
• Inspect for missing or mispositioned air deflectors, baffles, seals and
shrouds.
• The compressor cycling switch may not be operating correctly. This may allow
the evaporator core to freeze up or the compressor may not stay engaged long
enough for proper system pressures to develop.
• The air flow through the evaporator core may be restricted.
– The cabin filter may be plugged.
– The evaporator core may be covered with debris.
– The cowl air inlet leaf screen may by plugged.
• The A/C system may be overcharged or undercharged with refrigerant. The A/C
system charge weight can be measured with the RRR tool after a refrigerant
recovery is done.
• The A/C system may have an improper amount or incorrect type of refrigerant
oil.
• An A/C system sealer is not approved for use in GM vehicles.
• The vehicle’s refrigerant may be contaminated or contain an excessive amount
of air. The vehicle’s A/C system may have been charged with an unapproved
refrigerant. The refrigerant identifier on the ACR 2000 should alert the
technician to these conditions.
• The orifice tube or thermostatic expansion valve (TXV) may be restricted,
plugged or inoperative.
• The capillary bulb on the TXV must be properly positioned so that the valve
will provide proper refrigerant flow.
• The desiccant bag in the accumulator may have failed, allowing debris to
circulate in the A/C system.
• The A/C system charge weight may have been changed. Components with an updated
design may have been released. A check for service bulletins applicable to the
vehicle being worked on should always be done.
• A check for diagnostic trouble codes in all the control modules on the vehicle
should be done. Some trouble codes will disable compressor operation after they
have set. They must be repaired and cleared before compressor operation is
allowed.
• Verify that the engine is not operating with a low unstable idle, and that the
engine is operating within the compressor engagement parameters (for example,
the engine may be overheating or it may be too cold for compressor engagement).
• The diagnostic procedures in the HVAC section of the service manual should be
performed as written to prevent the misdiagnosis of a customer concern. The HVAC
Diagnostic System Check and the A/C System Performance Test are written for a
specific model only. They are not generic charts. They follow a logical order
with detailed instructions on how to perform each step.
• The Technical Assistance Center may be contacted for additional help and the
latest information on any unusual concerns.
When a thorough HVAC system diagnosis indicates that the compressor should be
replaced, follow the procedure in the appropriate service manual. The oil
balance instructions are an important part of the replacement procedure. The
correct refrigerant oil, as listed in the service manual, must be used in the
new compressor. It is recommended that a suction screen filter be installed on
Delphi Harrison compressors that do not already have one. The suction screen
filter is not approved for use on compressors from other manufacturers. Refer to
Corporate Bulletin Number 01-01-39-003A for more information on A/C suction
screen kit repair recommendations and procedures. If the compressor has had a
catastrophic internal failure, an inline filter may be required to capture the
large amount of debris that may be found to be circulating in the A/C system. In
addition, the A/C system may require flushing. Refer to Corporate Bulletin
Number 01-01-38-006B for more information on flushing procedures and
recommendations.
The addition of fluorescent refrigerant leak dye to the A/C system is
recommended if the vehicle does not have it installed already. Some vehicles
have leak dye installed at the assembly plant and this will be indicated on the
A/C charge label. Refer to Corporate Bulletin Number 00-01-38-009B for more
information. If leak dye has been added during a previous repair and has been in
the vehicle for more than three years, it is recommended that additional dye be
added. Finally, a leak check of the entire A/C system should be performed before
the vehicle is returned to the customer.
Courtesy of General
Motors.
AutoA/C Repairs Home
Updates
April 2006
USE IT - OR LOSE IT.
Operate the air conditioning at least once a week to keep the compressor shaft
seal lubricated. Failure to do so will result in the shaft seal drying out.
Shaft seal replacement is fairly simple but the compressor has to be removed
from the vehicle and the A/C system evacuated and re-charged when the compressor
is re-fitted. A costly exercise when switching the A/C on once a week will help
to avoid the seal drying out.
Use the air conditioning in winter together with the heater to reduce the
humidity within the vehicle.
Safety Switch
The safety switch is one of the most important yet
most overlooked
portion of the air conditioning system.
The function of the safety switch is to monitor high and low side pressure and
shut down the system if the pressure exceeds safe or drops below operating
limits.
The binary switch simply splices between the compressor clutch and
evaporator thermostat and taps into the high pressure line.
When pressures exceed safe limits, the switch opens the circuit to the
compressor clutch thus disengaging the compressor until pressure return to
normal.
The trinary switch operates much the same as the binary in that it shuts down
the compressor when pressures rise. However, the trinary also controls an
electric fan on the radiator that pulls additional air across the condenser to
bring pressures down.
Anti-Bacterial
The intrinsic nature of the air conditioning operation means that fungus and
bacteria can build up on the internal evaporator of the car (situated under the
dashboard).
This build up of bacteria can result in what is commonly known
as "sick car syndrome". Not only is an offensive smell given off whenever the
air conditioning is switched on , but occupants can feel sick or contract ear,
nose and throat infections from your system.
The potential for streptococcal infections from contaminated
Air Conditioning systems has been recognized for years particularly in
California where the infection occurs all year round and is widely referred to
as strep throat.
We treat the evaporator with a specially formulated Air
Conditioner anti-bacterial spray that kills all the bugs and leaves your air
conditioning smelling sweet.
AutoA/C Repairs Home
Applies
To: All A/C-equipped Honda models that use a heater valve cable.