: 1992-2004 Seville and Eldorado Basic a/c Diagnostics



mhamilton
06-03-11, 10:30 PM
Wanted to write up a few of the basics for common issues with this generation of Seville and Eldo ac systems. Hopefully this will help someone get some basic diagnostic info before posting specific repair questions. If anyone has any suggestions for changes or additions, please let me know!

Basic A/C Diagnostics for 1992-2003 Seville and Eldorado
also applicable to Deville and some earlier Cadillac models

First--unless you know what you are doing, do not guess how to make repairs or recharge an a/c system. At best the system could be discharged or components damaged, and at worst you can be severely injured by escaping refrigerant or over pressurized refrigerant containers. Explosions, burns, frostbite, blindness (among others) are all possible if a refrigerant system is mishandled. Always consult a factory service manual for exact procedures, or take the vehicle to a qualified a/c technician.

Second, please use the correct tools for a/c diagnostics and repair. The “single gauge recharge can” from an auto parts store is not the correct tool. A low pressure reading is practically useless without the high side reading. And stay away from “leak sealer” for ac systems. That snake oil has damaged more a/c systems than it ever fixed (see an example here (http://www.autoacforum.com/messageview.cfm?catid=20&threadid=21123)). The only accepted additive for an a/c system is UV dye for leak detection. And use sparingly—too much oil in the system can cause compressor damage. It only takes a small amount of dye to detect even the tiniest leak.

The typical Cadillac air conditioner problems fall into 2 categories—no air conditioning at all, or one side of the climate control is hot and the other is cold. The same basic checks can be made in both cases, though usually the latter the cause will be due to a fault in the air blend door (see the How-To on replacement elsewhere on this site for repair information). For problems with no cooling at all, you can skip the blend door checks.

One of the first and most basic checks for any issues on these models is to run a code check using the built-in diagnostics. See http://www.cadillacforums.com/forums/cadillac-seville-cadillac-eldorado-forum/138258-how-pull-codes-dtcs.html for specifics. The B codes on OBDII systems will point you in the right direction as far as faults. Many HVAC problems have nothing to do with a problem in the refrigeration system, so checking codes first is very important. However, not every component failure sets a DTC. Some codes might include:

B0419 - Air Mix Door #2 Range Error
B1317 - In Car Air Temperature Sensor
B1347 - Very Low A/C Refrigerant Warning

Or on OBDI systems:
B447 Very Low A/C Refrigerant Condition Warning
B440 Air Mix Door Problem

These codes are just a small example; there are many other components the BCM monitors related to the HVAC system.

If the codes point to an air mix door failure, then this will likely be the cause of “one side of the car is hot” type of problems. On 1992-1997 Sevilles and Eldorados, the air mix actuators are behind the glove box. On 1998-2004 Sevilles, the actuators are behind the dash on either side of the center stack. These can usually be examined for proper operation by removing some lower dash trim panels as needed (see actuator replacement how-to for more information). But, before jumping on replacing the actuators, some basic a/c system tests can be performed. In some cases, a slightly low charge will cause the driver’s side to be warm (not hot) and the passenger’s side to be cold, without setting any DTCs. This will usually be indicated by a warmer evaporator outlet temperature or lower than expected pressures.

To start with, the following items should be checked with the engine running and the a/c system on:
Does the compressor clutch engage and spin?
Do the radiator cooling fans both start?

The compressor should engage and stay on at idle for most temperatures above 80F. In cooler ambient temperatures the compressor will cycle at idle, but it should never rapidly cycle (every 2-3 seconds). Rapid cycling indicates a problem with the system and should be serviced before damage occurs.

The cooling fans will run in slow speed whenever the compressor is commanded on. Depending on PCM programming, the fans will change to high speed when high side pressure passes some threshold (about 220 PSI for R134a). This works independently of the PCM fan speed programming for coolant and transmission temperature (overheating coolant will disable the compressor anyway).

If these check out, then move on to checking the system performance. Pressure readings would be best, both the high and low side. For a quick check of a/c charge, feel the evaporator lines coming out of the firewall. Both should be near freezing and both should be close to the same temperature. The inlet to the evaporator is a small line, the outlet is a larger line. If the outlet feels warmer than the inlet, then the refrigerant charge is probably low. The best way to repair is by evacuating the system and recharging the proper amount by weight.

If the DIC displays “Low Refrigerant AC Off” then the compressor will not operate. When this code sets, the system is nearly empty and will need to be repaired (there is a leak if you have lost this much refrigerant), then evacuated and recharged by weight. If the message appears in the DIC, the system has stored either code B1347 or B447. The DTC must be cleared before the compressor will operate.

Charging and using gauges is an essential part of working on your own air conditioner systems, but this article was a basic tutorial. For all the technical information you could ever want on mobile a/c systems, visit www.autoacforum.com

Some other helpful links:
Evacuating and Charging (http://www.autoacforum.com/messageview.cfm?catid=20&threadid=7931)
Pressure Temperature Chart (http://www.ackits.com/aacf/ptchart.cfm)
http://www.autoacrepairs.com/index.html
http://www.firstfives.org/faq/AC/ac_charge.html
http://www.imcool.com/articles/aircondition/Auto_AC_Diagnosis.php
http://www.aircondition.com/tech/questions/82/Troubleshooting-with-Gauges-FAQ
http://www.aa1car.com/library/ac_recharging.htm