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Mobile Air Conditioning Service Report

Las Vegas, NV (January 2000)
Copyright AA1Car




Technical Resources:

1-800-890-4038 Chrysler Tech Authority Catalog

1-800-801-5420 Chrysler special tools catalog



3 generations of minivans

1984 -95 minivan "AS" seies minivans

1996-2000 "NS" minivans

2001 minivan is "RS"

HVAC diagnostic procedure:

1. Verify the customer's concern

2. Is he operating A/C system correctly? (covered in vehicle owners manual but many never read it!). Some customers may not understand best settings for optimum A/C. Using RECIRC provides maximum cooling. On minivans with dual (front/rear) A/C, driver control panel setting controls rear heat or A/C regardless of rear control setting. If you want heat in rear, must set front panel to heat. If want A/C in rear, must set front panel to A/C.

Chrysler has retrofit air filters for HVAC system.


PCM sends "on" signal to HVAC module.

HVAC module looks at evap temperature.

PCM looks at coolant temp, throttle position sensor, A/C pressure, crank sensor (engine rpm, must be over 500 rpm).

PCM grounds compressor clutch relay to run compressor.

Can use DART scan tool to reprogram vehicle PCM to improve HVAC performance. Several Chrysler technical service bulletins (TSBs) out that refer to flash updates to solve HVAC problems.

1996-early 1999 minivan radiator fan relay. Uses PCM controlled electronic relay to cycle cooling fans. Problem is it loses its heat sink, overheats & stops working. Screws break off.

On late 1999-2000 minivans, fan relay was relocated behind left headlamp for better cooling.

HVAC system uses variable fan speed. PCM uses duty cycle to control fan relay:

Low fan speed = 30% duty cycle

High fan speed = 100% duty cycle

Most minivans use expansion valve A/C system.

Most Jeep & truck use orifice tube A/C system.

Minivans with rear A/C have additional expansion valve, second "sub" condenser & evaporator.

Chrysler TSB out on cracked compressor lines. Torque on bolts that attach metal lines to compressor is critical.

2000 Chrysler minivans changed to a "long life" coolant. Heater core higher than radiator, so special procedure is needed to fill system. Must raise front of vehicle so radiator is higher than heater core, or can prefill heater core with coolant.


Three different types (some are mid-year model changes, control modules are not interchangeable, different connectors & diagnostic procedures). Easiest way to identify module is to look at connectors.

A/C pressure transducer, reads 0 to 500 psi.

0.15v = low pressure

0.45v = normal range

3.0v = pressure too high

Thermistor used in evaporator to read evap temperature. Sensor works like coolant sensor to read evap temp. Controls A/C request to PCM to cycle compressor clutch.

Control head monitors blower speed and evap temperature. Software allows evap temp go lower (cooler) than normal if blower at high enough speed without freezing up.

Flashing LED diagnostics - see chart in Chrysler NS Minivan A/C book page 113.

Calibration needed to learn potentiometer values of blend control door motors. System must pass diagnostics and cool down.

Failure codes listed on page 120 -- displayed with flashing LEDs early models, or scan tools on later models.

On 1996-98 HVAC conrol heads, can use LEDs to check operation of control

switches. LEDs flash at faster rate

DART scan tool (Diagnostic And Reprogramming Tool) Chrysler dealer & aftermarket tool for flash reprogramming and troubleshooting. It can read fault codes, but not sensor data like a scan tool. Only costs about $1000 compared to about $4300 for Chrysler DRB III scan tool. DART can also be used to reprogram security keys for ignition system.



What is new for 2000 on Ford vehicles:

Scroll compressor replaces FS-compressor. Can scroll compressor be swapped for older FS compressors? Ford says no. The engine mounts are the same but the clutch and hose connections are different.



Some differences:

Lincoln has hydraulic cooling fan, Jag S has electric cooling fan (electric fan will be phased out in a year or two).

Jaguar has optional voice activated cooling control.

Both use a thermal expansion valve and scroll compressor rather than orifice tube & regular compressor. Eleven factors control compressor operation. 10 are run by PCM, 11th is thermal protection switch.

Must perform engine diagnostic scan when troubleshooting A/C compressor clutch problems.

DATC has no blend door. All temp control regulated by water valve that regulates coolant flow thru heater core. Coolant control valve has two duty solenoids & valves. Heater core is split into two halves for dual zone heat control. An auxiliary water pump is used on V8 & diesel engine to help circulate coolant to heater core.

New DATC components, inputs & outputs

DATC module powered at all times.

Heater core coolant control valve (contains 2 valves).

No voltage is 0 duty cycle = 100% coolant flow.

Voltage = 100% duty cycle and no coolant flow.

Driver input will vary coolant flow to either side of heat core to regulate temp.

Electric water pump required to maintain high coolant flow to heater core used on V8 & diesel only. Pump may run after engine has been shut off to help cool engine cylinder heads to reduce heat soak during hot weather.

Evaporator discharge air temperature sensor (a deicing switch). Prevents evaporator freeze up.

Hydraulic cooling fan is a georotor design pump motor. Receives hydraulic fluid from a small belt-driven pump on the engine.

Heated windshield wiper rests at base of windshield. Electric grid in glass heats up wipers to melt ice. 3 modes are auto, on and off. Auto turn on heater is outside temp below 40 degrees. Before it turns on, it checks battery voltage. If battery low, it will not come on.

Strategies & diagnostics for Lincoln/Jag dual zone a/c system:

Compressor is on in all distribution modes unless it is below 35 degrees F outside. Exterior temperature sensor updates depending on vehicle speed. It is delayed at idle to compensate for heat transfer from under the hood. Prevents misleading exterior temp readings.

The zone temp readings given to driver are different from passenger. Driver gets max, but passenger only reads 65 to 85, this allows driver to override passenger inputs.

Auto temp balance: If hold AUTO button for 2 seconds, automatically changes passenger setting to drivers setting.

Timed RECIRC door. In defrost mode, runs 2 to 20 minutes.

Voiced activation commands on Jag S only (not Lincoln LS). 6 commands you can give it. Say "CLIMATE CONTROL ___" for temperature settings , defrost, etc. To activate, push button on steering column. Microphone in steering column picks up voice commands.

Jaguar S-Type HVAC control head has no self-diagnostics. Use OBD II to diagnose. Can test sensors and wires, but have to use OBD II to get sensor readings, control flow control doors, water pump, etc.


What is new for 2000-2001

GM Compressor problems:

New GM double lip shaft seal service kits to eliminate leakage that can cause clutch to slip.

GM says to install inline filters if system contaminated. Also, install suction screens if system contaminated. Available from Kent-Moore, (J44551 kit includes screen and installation tool (bolt)).

System flushing. Use only when severe oil contamination or overcharge is suspected. Use J42939 flushing tool, and use R134a only on R134a systems. Do not flush compressor. Remove it and valves. GM will have a new refrigerant flushing TSB out in spring of 2000.

1996 - GM introduced new slimline seal washer on S10 compressor block. Must use proper slimline washer or it will leak. Do not double up washers. No need to lubricate like o-rings.

Refrigerant contamination - mixed R12 & R134a can cause evaporator freeze-up. Creates a different pressure.

1996-98 Chevy Blazer, S10, GMC with 4.3L V6. Vehicles equipped with Dex-Cool. If cooling system low, creates red sludge that plugs up entire cooling system. TSB 99-06-02-012 covers cooling system flushing procedure to remove crud.

1997 and earlier cars & light trucks. Repeat aluminum heater core failures.

Caused by depleted corrosion inhibitors in coolant (maintenance neglect).

Flush system to remove rust & crud.

Poor cooling 1996-99 Astro minivans with dual A/C, rear hose rubs

through and leaks. TSB 99-01-38-002

1997-99 Buick Park Ave, inaccurate HVAC readings and ticking noise.


DELPHI HARRISON warranty analysis of compressor showed that failures are being caused by:

Use refrigerant only says GM..

All Delco Harrison compressors shipped with info on which lubricants and dyes are approved for use.


ACR 2000 -- Next generation of A/C refrigerant recover equipment for GM dealers. Being introduced now. Problem is technicians are not purging air from recovery tanks. Leads to air contamination when recharging vehicles. GM found many dealers had a/c equipment that was in poor condition, causing warranty problems. Also found cross contaminated refrigerant can be prevented by using Pure Guard refrigerant identifier. Nine out of 10 vacuum pumps had not been serviced. Sumps were full of oil.

New ACR 2000 features:

Trend in new vehicles is to smaller a/c system capacities, so requires higher degree of charging accuracy for good cooling performance. Low system charge can cause compressor noise.

In a 2 lb. system, a charging accuracy of plus or minus 6 oz can create a 19% over or under charge. ACR 2000 is accurate within 1 oz, or plus or minus 3% -- is much more accurate.

Same features are being built into aftermarket a/c recovery/recharging eqpt: Snap-On, Robinaire, and others.



SAE specifications for leak detection dyes:

Each compressor mfr has their own specs for dyes. Most dyes met SAE specs and are probably ok to use, but some do not meet specs and can cause problems (no names mentioned).


HVAC control head costs $830 !!!!!! to replace. Make sure it needs to be replaced, may be a sensor problem or something else.

Most modules operate at 5 volts. Brain of module is CPU (central processing unit) most only run at 33 mHz. Most HVAC modules only about 6K of RAM memory. Use EPROM for program storage calibration. It allows software to be flash upgraded.

Modules can be damaged or mis-set if ignition is on and battery is reconnected.

If reprogramming a module, battery voltage must be at normal 12.65 volts, otherwise module may not accept flash program properly and may freeze up (go dead).

Using cell phone or two-way radio can produce RFI (radio frequency interference) that upsets operation of HVAC control unit. Cure is to install PN 122205 is RFI noise filter for HVAC.

Use braided wire to ground module. Braided wire does better job of suppressing RFI than regular wire.

GM has a dealer only hotline for solving EMI/RFI problems: 1-800-428-0501

More Air Conditioning Articles:

A/C Cooling Problem: Blows Warm Air Only No Cool Air

Troubleshooting Air Conditioning Problems

Troubleshooting A/C Cooling Problems with Temperature

How To Recharge Your Car's Air Conditioner

Refrigerant Contamination

Alternative Refrigerants

New Refrigerants & A/C Systems

California proposes ban on R134a sales to motorists

Retrofitting older R-12 A/C systems to R-134a

MACS Recommended A/C Service Procedures (PDF file - requires Adobe Acrobat Reader to view).

Automatic Climate Control

A/C Compressor Failures

A/C Condenser Flushing

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