ImperialCrown wrote about the common problem of having cold air coming from one vent and hot air from another: For other auto air conditioning solutions, click here. This article briefly describes the control system of computer controlled air conditioning systems which are typical of Chrysler vehicles which do not have automatic temperature control. This system is also similar to that of other manufacturers' products. The following components are used: 1). An electromagnetic a/c clutch. 2). The fan relay (the relay is a double-pole-single-throw type; 1/2 is used for fan control whereas the other 1/2 is used in the relay logic circuit used to control the a/c clutch). 3). The wide-open throttle (WOT) cutout relay. 4). The pressure cycling switch. 5). The switches used to select air conditioning: defrost and a/c. The point marked "to ecm" is drawn to a positive value via a pull up resistor on the computer's board. The pressure cycling switch is used to prevent ice formation on the evaporator's core (this would obstruct air flow and cause system overheating).

The WOT cutout relay is a normally closed one; it is energized (opened) by the ecm if the ecm detects a WOT condition -- this reduces engine load during high power demand. The fan relay is energized by the computer when cooling is required, a/c is required, and, under appropriate conditions, for radiator demisting (to reduce steaming when the vehicle's engine is on, but the vehicle is not moving). The clutch is an electromagnetically controlled "brake" which is attracted to the compressor when current is supplied; the friction material ensures that, if the clutch is working properly, the compressor will fully engage. The surge suppressor on Chrysler products is often a pair of zener diodes mounted back-to-back in the (polarized) connector going to the clutch. Operation of the system is as follows (assume that the car is not near WOT): The compressor is now on. The compressor will continue to be on unless WOT is reached or the pressure cycling switch opens. The process then repeats.

The following readings were taken using an OTC 500 meter and OTC current measuring clamp; they are off of a 1986 Le Baron: A common failure is the fan switch's resistance increasing. Indeed, these switches are known to melt from overheating. On 1980s products, this switch is a replaceable item (about $18) -- the entire pushbutton assembly does not require replacing. Here are some problems I ran across in my Le Baron: 1). BAD FAN SWITCH The switch didn't overheat, but caused an insufficient current to be delivered to the clutch. sleeve air conditioner units london ontarioThis caused the clutch friction material to overheat, which caused the clutch to float on a layer of gas. ac window unit repair new orleansThe symptoms were (1) gradual reduction in cold air delivery and (2) smoking refrigerant oil (leaking from a 9 years old compressor front seal).ductless ac units mitsubishi

2). BAD PRESSURE CYCLING SWITCH AND CONNECTIONS The pressure switch had bad intermittent connections; also the terminals in the external connector were corroded. The symptom was the a/c cycling on and off about three times per second (recall that the computer's timer is set to something between 300 and 400 ms). Copious use of television tuner cleaner and polishing the blade terminals on the switch would temporarily eliminate the problem. The fix consisted of replacing the switch (aftermarket bought from a parts jobber -- about $30), replacing the terminals in the connector (available in any hardware store), and spraying the connectors' boot with silicone lubricant (for a weatherproof seal). The original terminals were merely crimped; I crimped and then soldered the connections. You will require the factory manuals (or equivalent information) and a high impedance multimeter. If a digital meter is used, it must have a bar graph display since the digital display with the dual-slope integrating analog to digital converter will react too slowly to changes in the circuit.

A min/max function is also useful to have. The voltage drop from the clutch to the battery's negative terminal MUST be low when full operating current is seen -- about 700 mv maximum is ok. In my case, after all repairs were made, the voltage was between 400 and 500 mv. For one test, I disconnected the clutch and replaced it with an unpowered test light -- this allowed me to check voltage drops with the a/c always on (pressure cycling switch would never open). Although full current was never approached (the light draws only about 300 ma), I did find bad connections. Measuring individual voltage drops is the ONLY reasonable approach. Once problems are found, resistance measurements can be used to home in on target components. For example, I found bad electrical contacts by isolating the problem to the pressure cycling switch, then turning off the engine, disconnecting the WOT cutout relay connector, and measuring resistance from the battery's negative post to the WOT connector.

Moving the terminals on pressure cycling switch's connector showed a huge decrease in resistance. Television tuner cleaner didn't reduce the resistance too much, so the terminals were replaced. Ed Hennessy said one problem with 1980s Chrysler a/c systems is leaky hose fittings, which leave a tell-tale slimy residue near the metal fittings at the rubber hose connections. Another is a leaky compressor shaft seal, which can (contrary to what 'they' may tell you) be re-sealed with a gasket. For other auto air conditioning solutions, click here.Cadillac SRX vehicles recalledThe driver's seat may have been built with an incorrect seat track bracketVolkswagen recalls vehicles with fuel rail sealing cap issuesFuel could leak into the engine compartmentDodge Dart Aeros recalledThe Tire Pressure Monitoring System warning light may fail to illuminateVolkswagen recalls Jetta with headlight issueThe light output from the headlights may be insufficientFCA recalls Dodge Rams, Dakotas and Mitsubishi RaidersThe return springs in the clutch ignition interlock switch may breakNissan recalls ArmadasThe parking pawl may not engage

fullyBeemers with air bag inflator issue recalledExcessive internal pressure may cause the inflator to ruptureMINI Cooper Hardtops recalledDrivers may be able to exit the vehicle when the transmission is not in ParkHonda recalls Acura RLX vehiclesOutput of the headlights may be diminishedFCA US recalls nearly 3 million vehicles with air bag inflator issue Excessive internal pressure may cause the inflator to ruptureHyundai recalls 1.6 liter SonatasThe vehicles may have been assembled with an incorrect left axle shaftHonda recalls Crosstour vehiclesThe inflator tube for the side curtain air bag may have been manufactured incorrectlyToyota recalls model year 2015 SiennasThe second row overhead assist grips may detach deployment of the curtain shield airbagAcura TLX vehicles recalledThe transmission may not be able to shift into the Park positionSoutheast Toyota Distributors recall vehicles with seat heater issueCompression of the seat cushion may damage the seat heater wiringFord recalls older Mustangs and GTsExcessive internal pressure may cause the airbag inflator to ruptureFCA recalls Dodge Challengers

The instrument cluster may become inoperativeMustangs with fuel line issue recalledThe fuel pressure sensor may not have been seated properly to the fuel jumper lineChrysler recalls Dodge Ram 1500 trucksThe rear axle pinion nut may loosenFord issues regional recall for Ranger and GT vehiclesExcessive internal pressure may cause the air bag inflator to ruptureBMW recalls MINI Cooper Hardtop 2 DoorsThe driver and front passenger seatback adjustment mechanism may not be fully engagedGeneral Motors is recalling 679 vehicles equipped with electric power steeringThe vehicles may experience a sudden loss of power steering assistToyota is recalling 5,650 vehiclesThe left-side front suspension lower arm may have been manufactured incorrectlyChrysler expands recall of vehicles with air bag inflator issuesThe company says it's unaware of any accidents or injuries related to these inflatorsFord recalls F-150 with brake pedal issueThe brake pedal position switch may not be adjusted properlyDodge Journey vehicles recalledTire placard labels may contain inaccurate information BMW recalls X5 vehiclesThe seat belt attachment could

break and fail to restrain an occupantFord recalls Mustangs with seat belt issuesThe passenger safety belt tension sensor may misclassify the size of the front passenger seat occupantBMW recalls X3 and X4 Sports Activity Vehicles The driver's side exterior rearview mirror may not meet federal safety standardsFord recalls vehicles with steering issuesThe problem could result in a loss of steering controlFord recalls F-150 and Flex vehiclesThe vehicles have a reduced clearance between the seat frame and the seat track assemblyHyundai recalls Genesis and Equus vehiclesThe stop lamps may not illuminateNissan recalls various vehicles with fuel pressure sensor issueThe fuel pressure sensor may loosen and cause a fuel leakVolkswagen recalls BeetlesThe glass sunroofs may breakHonda recalls Grom125 and Forza motorcyclesThe fuel pump could failBMW recalls i8 vehiclesThe fuel tank could leakGulf States Toyota recalls TacomasThe vehicles may contain an incorrect Load Carrying Capacity Modification labelGeneral Motors recalls Chevrolet Colorados and GMC CanyonsThe driver air bag connections may have been wired incorrectlyChrysler