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Dick Hussey's Tech Corner

The HVAC System in Your Allanté

Allantés are equipped with a sophisticated thermostatically controlled heating/air conditioning system. The following is the first article in a series that will explain how the system works, and perhaps provide a few tips to help you operate the system in a more efficient manner. This section will focus on the cooling portion of the system.


The major components of the system are divided into three groups : the refrigeration system for cooling, the heating system for

heating, and the air delivery system to get the heating and cooling to work together to reach the desired temperature inside the car.


The refrigeration system is the most expensive to repair. The AC compressor, condenser , and evaporator core all can fail and need to be replaced. Each of them is expensive, especially the compressor and the evaporator core. There are a number of connections in the system, each of which can leak. There are high side temperature and low side temperature sensors, a low-pressure cycling or cutout switch, the orifice tube, and receiver drier or accumulator. Each has an important role to play in the proper operation of the system.


The best known component of the system is the AC compressor. There are 4 different compressors used across the Allanté production years:


1) 1987 and 1988 take one version

2) 1989 through 1992 take another version

3) 1993 early models take a third version

4) 1993 V4J models take the 4th version


Delco has discontinued the early 1993 version and no longer lists this compressor in their catalogs. So when searching the catalog

now, it looks like 1993 models all rake the same compressor. In spite of what the catalog shows, this is not the case. Nothing has changed with respect to the fact there are two different compressors. The way to tell which one you need is to check the production options code in the trunk of your 1993 Allanté. If the "V4J" option code is shown on the tag, you need the later version, the compressor shown listed in the current Delco catalog. If the V4J code is not shown , you have the early version 1993. There are a finite number of these compressors remaining. Only about the first 1500 1993 Allantés produced utilized this compressor , so apparently there is not enough incentive to produce more for such a limited market . The compressor will bolt into the car OK, but the hose manifold assembly is different and will not line up with the ports on the back of the compressor. If the hose manifold assemblies for the later model Allantés were available, replacing both might be an option, and utilizing the later compressor . Unfortunately, these new hose manifold assemblies have not been

available for years. Often when there is a problem with the hose manifold assembly, the only option is to have the old one repaired.


Another problem area with replacement pans is the hose manifold assemblies on 1987 through 1990 models . These pans have all been discontinued as well, but the last catalog listing shows one version as fitting 1987 through 1990 models. This is not the case. The 1987 and 1988 model Allantés have an air pump as part of the emission control system. The 1989 and 1990 Allanté models

do not. The hose manifold assembly listed to fit all 1987 through 1990 model years only firs 1989 and 1990 models . That hose manifold will not clear the air pump on the earlier models . A used 1987 or 1988 hose manifold assembly would probably fit 1989 and 1990 models, but I have never tried to see if this is the case.


Average AC compressor life seems to be about 60,000 miles. As they have aged, many very low-mileage Allantés have encountered compressor failure at less than 60,000 miles. Often what happens is that the compressor shaft seals start leaking, so the system has to be recharged frequently. That type of failure is the best type to have, before the compressor destructs internally. If the compressor destructs and fills the downstream system up with debris, repair costs can increase dramatically . Rather than just facing a compressor replacement, often the condenser (in front of the radiator) must also be replaced. The evaporator core (on the firewall outside in front of the passenger) usually is protected from debris by the orifice tube, a small filter inside the Freon piping line. Whenever a new compressor is installed, the orifice tube and receiver/dr ier (sometimes called the accumu lator) must also be replaced.


When replacing the compressor, the old unit can be slid out in front of the right front wheel. The splash shield parts in that area must be removed. It is usually helpful to remove the engine cooling fans to gain easier access to the 15mm bolt that holds the hose manifold assembly to the back of the compressor. The condenser can be changed easily. It is located in front of the radiator. The evaporator core is another matter. That part is located on the firewall in the engine compartment in front of the passenger. The back of the engine does not have to be lowered in order to replace the evaporator core. The front of the engine cradle can be disconnected from the frame rails and lowered a few inches , which will pivot the engine away from the

firewall. Yes it will still be tight back rhere, bur that will provide enough clearance to sneak out the outer ductwork after it has been unbolted from the firewall. Once the outer duct has been removed, the evaporator core is easily accessed.


Many Allanté refrigeration systems have been converted to R134a Freon. The system will perform just fine with R-134a. If it does not, something is wrong on the car, it is not the R134a Freon causing the problem. When converting to R-134a, we ALWAYS replace the receiver/drier and orifice. Many Allantés, perhaps even most Allantés, will show a false low Freon message when the outside temperature drops below 80 degrees F. The reason for this: Freon pressure is not actually measured, but rather it is calculated. Either there is a glitch in the calculation or some aspect of the calculation has too eight a range under some conditions. Adding a little more Freon sometimes, but not always, corrects this condition. If the compurer has shut off the compressor, it will not restart automatically. It has to be restarted. There are two ways to do this, either by disconnecting the battery for 30 seconds then reconnecting it, or by clearing the relevant stored trouble codes (B446, B447, and B448). Procedures for clearing stored trouble codes can be found on our website at www.Allanté then look on the left menu for the topic.


The heating portion of the system is much simpler. The heater core is located inside the car behind the glove box. The heater hose connections are located behind the right strut tower. Heater cores can have one of two problems, either they can leak or get clogged. If you start to smell antifreeze inside the car, find chat you are losing coolant but cannot see any leaks under the car, or find a leak over by the evaporator drain, chances are your heater core might be leaking. The usual symptom is wetness of the passenger side floor carpet. If you catch it early enough, the dampness may be limited to the foam padding on top of the plastic trim panel over the passenger's feet, the one that mounts the passenger side courtesy light.


A clogged heater core and an airflow problem can have the same symptoms- no heat. Troubleshooting the airflow problem will be covered in the next article. If the heater core is found to be clogged, usually it can be Bushed to restore Bow. Drain about a gallon of antifreeze out of the cooling system. Then remove the heater hoses from the engine coolant pipes. Take a garden hose and use water pressure back and forth between the two heater hoses to blow out the debris clogging the heater core. This can cake multiple attempts back and forth.