Cadillac Repair: 1989 Cadillac AC, fan buttons, core leak

Question
Hi, I have a 1989 Cadillac De Ville and it has no air, the AC compresser is not engaging. I have the default codes they are E48 E52 and F48. I was wondering if it was the CCM or the AC power module or is it something else? Thanks, Dennis

Answer
Hi Dennis, The key to this problem is the F48 code because when it sets it will disable the compressor from operateing. It could be a defective low pressure switch but what it probably is is that the system is low on freon because the evaporator core has a leak.

    The way to diagnose this problem is to hook up gauges to the low and hi side fittings and see what the pressure is. I would expect that the pressure on both gauges to be aprox. what the ambiant temperature is if there is enough freon. So if the temp is say 100 and the pressure is 70 or less then there is a leak big enough or over a period of time that allowed the freon to leak out.

    To clear the codes and allow the compressor to engage start the engine and press off and warmer on the climate control panel and hold them for 4 seconds or until it goes into diagnostics. When all the codes have displayed press the off and hi fan buttons and that will clear the ECM codes...off and low fan to clear the BCM codes. Turn off the key and then restart the engine and sellect auto and if there is enough freon in the system the clutch will now engage provided the low pressure switch is ok.

    To check for an evaporator core leak remove the power module that is located on top of the blower motor houseing on the RH side. Once that is removed shine a light on the core and if it is oily near the bottom then it will need to be replaced before the a/c will work propperly. Under no circumstances should you install any sealer in the system to try to get it to seal because the sealer usually does more damage than good but more importantly you might not find a shop willing to repair the a/c because the sealer will damge their recycleing machine.

     The problem could turn out to be with the CCM or power module but check the freon level and system for leaks first. If that is ok then checking those items would be next.

     As for the E48 it is an EGR code and the E52 means the ECM lost battery voltage.

     Let me know if you need anymore help. Bill