ACTION NAPA AUTO Parts - (Page 37)
System charge
determination
By Ward Atkinson (Bill Hill, MACRAE LLC, contributed to this article.)
C
onversion vehicles which have additional cooling units added to the OEM's production front end
A/C systems present a special challenge: establishing the "new" system's correct refrigerant and lubricant
charge amounts.
Modification of a Production A/C system with
additional evaporator
Vehicle manufacturers establish A/C system charges in
an environmental test facility by running a charge determination test procedure at high ambient load conditions.
Since companies in the conversion industry normally
do not have access to a test chamber, there is a method (detailed below) that can provide some guidance by operating
the modified vehicle under high load weather conditions
to develop an on-road system refrigerant charge curve.
Electronic scale
Consideration for different system designs
There is a large variety of A/C system designs used in
today's vehicles. They can include systems with orifice
tube expansion devices with low side accumulators, systems with thermal expansion devices, high side receivers
(some with multiple receivers) systems. Others can have
internal heat exchangers, systems with condensers that
have built-in receivers and integrated sub-cooling loops,
and systems which utilize both refrigerant-to-water chillers as well as refrigerant-to-air evaporators.
Some of these systems have very low refrigerant charges approaching 350 grams, and the amount of reserve
charge that is designed into the system varies by vehicle
manufacturer. This makes the conversion of an OEM production A/C system more complex. Some vehicle conversions also add an additional auxiliary condenser that will
increase the amount of refrigerant required for operation.
Establishing system charge
Environmental test facility
The procedure begins with evacuating the system and
installing a small amount of refrigerant as a starting point
to develop a charge curve from which the final charge
amount can be determined. Then the vehicle is operated
Spring 2015 * ACTION/NAPA
37
ACTION NAPA AUTO Parts
Table of Contents for the Digital Edition of ACTION NAPA AUTO Parts
Engine Cooling Systems: Electric cooling fan operating strategies
The next 609 is here
Computer controls for air conditioning compressors
Getting legal
Mechanical fan clutch diagnosis
Properly mixing coolant
Selling the right things
Ford 6.4L Powerstroke
A big bad leak, but where
Recovering the entire charge
Blower Motor Mystery
Case Study: 1999 Jetta A/C Fuse
System Charge Determination
ACTION NAPA AUTO Parts - Cover1
ACTION NAPA AUTO Parts - Cover2
ACTION NAPA AUTO Parts - 3
ACTION NAPA AUTO Parts - Engine Cooling Systems: Electric cooling fan operating strategies
ACTION NAPA AUTO Parts - 5
ACTION NAPA AUTO Parts - 6
ACTION NAPA AUTO Parts - 7
ACTION NAPA AUTO Parts - The next 609 is here
ACTION NAPA AUTO Parts - 9
ACTION NAPA AUTO Parts - 10
ACTION NAPA AUTO Parts - 11
ACTION NAPA AUTO Parts - Computer controls for air conditioning compressors
ACTION NAPA AUTO Parts - 13
ACTION NAPA AUTO Parts - 14
ACTION NAPA AUTO Parts - 15
ACTION NAPA AUTO Parts - Getting legal
ACTION NAPA AUTO Parts - 17
ACTION NAPA AUTO Parts - Mechanical fan clutch diagnosis
ACTION NAPA AUTO Parts - Properly mixing coolant
ACTION NAPA AUTO Parts - 20
ACTION NAPA AUTO Parts - 21
ACTION NAPA AUTO Parts - Selling the right things
ACTION NAPA AUTO Parts - 23
ACTION NAPA AUTO Parts - 24
ACTION NAPA AUTO Parts - 25
ACTION NAPA AUTO Parts - Ford 6.4L Powerstroke
ACTION NAPA AUTO Parts - 27
ACTION NAPA AUTO Parts - A big bad leak, but where
ACTION NAPA AUTO Parts - 29
ACTION NAPA AUTO Parts - 30
ACTION NAPA AUTO Parts - Recovering the entire charge
ACTION NAPA AUTO Parts - Blower Motor Mystery
ACTION NAPA AUTO Parts - 33
ACTION NAPA AUTO Parts - 34
ACTION NAPA AUTO Parts - Case Study: 1999 Jetta A/C Fuse
ACTION NAPA AUTO Parts - 36
ACTION NAPA AUTO Parts - System Charge Determination
ACTION NAPA AUTO Parts - 38
ACTION NAPA AUTO Parts - Cover3
ACTION NAPA AUTO Parts - Cover4
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