Originally released July 1992
“The climate control system in a car is very important to a customer because it’s something he or she operates every day ... and it affects their subjective opinion of the overall vehicle,” noted Stan C. Surratt, manager — Climate Control for Chrysler’s Large Car Platform Team. Gone are the days when heating, air conditioning, and engine cooling/air flow were separate development areas at Chrysler. “We’ve integrated all those functions into one group called Thermal Systems. Total climate control can’t be taken for granted any more.”
Chrysler LH Thermal Systems engineers were painstakingly responsive to extensive field research that told them early in the program precisely what features consumers wanted most. Among these:
“From the very beginning, our goal was to build a system based on what we thought the customer wanted,” said Surratt. “And our objective was not to be just best-in-class, but the best in the world.” To do this, Chrysler benchmarked the BMW 7 Series.
In developing the climate control for the LH cars, engineers were confronted with an entirely new variable in the equation, the air conditioning performance of the environment-friendly chemical refrigerant, R134A, which contains no chlorine and replaces the ozone-threatening Freon for air conditioners. Government regulations demanded the transition to the new, less efficient, and more corrosive refrigerant.
The LH cars are believed to be the first in the world whose entire climate control system is electronically managed by the vehicle’s body controller. The electronics governing the Chrysler-designed system are so sophisticated that 19 patent applications were made. Also new to the LH cars among Chrysler products are combined rear-seat air conditioning/heating ducts, a feature normally found only on selected high-end luxury cars.
Months of actual road testing under all types of weather conditions — from a record 122 degrees Fahrenheit in the desert Southwest to a minus 40 degrees in northern Canada — convinced Chrysler development engineers that the LH climate control system could handle almost any extreme condition ... or anything between.
“I think we spent more time on the road with these cars ... about 150,000 miles in total ... than any engineering group, except maybe the people at the Proving Ground,” ventured Surratt.
In addition to the city streets of several major cities and on highways across the country, the LH climate control systems were tested on the mountain grades of the Rockies, in Death Valley and up Pikes Peak.
The heating/air conditioning/engine cooling systems for the LH cars are the most powerful Chrysler has ever developed, and among the most powerful anywhere. Air flow into the passenger compartment is 50 percent greater than on any previous company model, due largely to another new Chrysler design —the dual-scroll fan.
The heater is capable of dispensing 40,000 BTUs per hour, roughly the equivalent of a 40-gallon home hot water heater. The AC system is rated at 23,000 BTUs per hour, roughly equal to a two-ton home AC system. It is big enough to cool a 1,500-square foot home. The LH engine cooling system overall absorbs some 163,000 BTU’s per hour of unspent heat from the engine.
“So you can see, we’re dealing with an awful lot of energy,” noted Surratt, who firmly believes the LH cars can be heated or cooled more quickly than any vehicle Chrysler has ever built.
To illustrate, on a scale of 1-10 in occupant comfort ratings, a control system that achieves a minimum comfort level of five — either heating or cooling — in four minutes is considered exceptional. “Anything above a five-rating in four minutes is just a question of the comfort level an occupant wants,” said Surratt, who noted that a majority of vehicles on the market today achieve a five on the 1-1 0 comfort scale in about 7-1 0 minutes. “We targeted a five rating in four minutes for LH, and we’ll be there,” he added.
The fact that the Intrepid, Concorde, and Vision (and the later Chrysler New Yorker and LHS) have exceptionally large passenger compartments posed no real problems for climate control engineers.
“If there was any challenge, it was in the glass area,” said Surratt. “There is just so much of it on these cars — up to 25 percent more than some past and present Chrysler vehicles — that we had to be doubly sure we had enough AC and heater capacity.” The oversized windshields (1 5 cubic feet) are raked to a 63-degree angle and are constructed entirely of solar glass.
There actually are two types of solar glass — one that absorbs the sun’s energy and another that reflects it, Surratt hastened to point out. “The solar material on LH absorbs the heat,” he explained “The outside air flow over the glass takes that heat away. It doesn’t get into the interior of the car at all. There is also a significant reduction of infra-red and ultra-violet rays that penetrate the passenger compartment. In the final analysis, though, we regard the solar glass windshield as a big plus to the climate control on this car.”
“The amount of heating you have available is basically the function of the amount of heat rejection by the engine,” said Surratt. “With this particular car, because the engines (standard 3.3-liter and an all-new, optional 3.5 powerplant) are both V-6’s, there is a lot of heat available. We were blessed.” The smaller the engine — a 4-cylinder, for example — the less heat it rejects, reducing the available excess energy needed for engine cooling.
“There is just so much energy available,” continued Surratt. “The horsepower generated by the engine requires the bulk of that energy. What it doesn’t use is given up in the form of heat. The cooling system takes that heat away from the engine so it doesn’t destroy itself.”
It is that rejected energy that the cooling system utilizes to keep the engine, transmission and other powertrain components operating in temperature ranges acceptable for long-term durability.
“Actually, customers don’t want to know anything about a car’s cooling system,” said Surratt. “And one of our major objectives was to develop a cooling system that the customer didn’t have to think about at all. It should be there and just do the job.
“LH has a high capacity system and it works very quietly. When the fan comes on, it is virtually inaudible. In fact, there are two fans that operate at two different speeds and you can hardly hear either of them.”
Climate control engineers developed Chrysler’s first dual-scroll fan in which two fans are mounted back-to-back, one with the blades aimed upward the other downward. Both are driven by the same motor. “It may be geometrically complex, but the benefit is that we have two fans in the space of one before,” said Surratt. “Available space under the hood is limited because the engine itself takes up such a large area. Before, the space beneath the engine was pretty much a dead area. What the lower fan does is circulate that bottom air. It helped us get 50 percent more available air flow with the same motor power and less noise than with two separate fans.”
This dual-scroll fan system — with the AC blower at its highest setting — injects 310 cubic feet per minute (CFM) into the passenger compartment. By comparison, a [EEK-style] Chrysler New Yorker AC system passes about 220 CFM through to the vehicle interior at a maximum setting, using about the same power to the fans.
Use of the new chemical refrigerant, R134A, instead of the previously-employed Freon in the air conditioning system, raised two particular challenges for Chryselr LH climate control engineers.
First, R134A does not transfer heat as efficiently as Freon and, therefore, required a larger condenser to achieve the same capacity. Secondly, because the molecules in 1 34A are smaller, it necessitated tighter sealing techniques for hoses and gaskets, as well as new, less porous material for these components. A higher-capacity condenser, with four parallel passages was developed to overcome the reduced efficiency level of R134a. Traditional condensers contain a single passage for Freon. The new condenser also is constructed of aluminum for reduced weight. “With the exception of a slightly larger compressor, the AC system performance a customer perceives with R134a will be identical to the old system,” contended Surratt.
Historically, electronics for climate control systems were engineered separately from other body/chassis systems.
“The only place we’d interface with the rest of the systems was at the battery,” mused Surratt. “We had our little box (computer) and the body engineers had theirs. In this project, we integrated the entire control logic of the automatic temperature control system (ATC) into the main body computer.”
By eliminating a second computer for the climate control system, Surratt estimates a considerable per-unit cost savings on the LH vehicles.
Expanding software memory capacity to handle the climate control function added some costs to the body computer, but these were more than offset by the savings achieved in eliminating a separate computer and reducing the total number of sensors. In addition, the entire climate control system now can be analyzed for dealer service technicians by Chrysler’s hand-held DRB II diagnostic module. Previously, a trial-and-error method prevailed with only repair manuals as a guide.
Ean Orsel pointed out - as many owners already know - that this was, unfortunately, not the end of the story. Ean wrote: “I laughed because my Dad owned a 1993 Intrepid that needed the evaporator replaced 6 times under warranty. Reason: They are made of aluminium and corrode in the wet enviroment they create. We were told the proper solution would be to make them out of brass.”
Like just about all manufacturers, Chrysler had problems with the corrosive properties of the new refrigerant, as well as its efficiency problems.
Chrysler extended the warranty of its air conditioning units in the LH series, but many customers were alienated.
The First Transistor Radio
All Mopar Car and Truck News
FCA at the Eiffels
Chrysler: Port Melbourne