rgh1016 Posted March 23, 2006 Report Share Posted March 23, 2006 I have recently experienced fault code B-1347 (Low Refrigerant). Resetting the code permitted the a/c to again operate for a while, but the air output from the evaporator was only cool at best even with the temp control set at 60 degrees. A check of the low-side pressure showed 38 psi (normal) but there is noise emanating from the accumulator anytime the compressor is engaged. This noise is loud enough to be heard inside the car and at first I thought it was coming from the compressor since it was present only when the compressor clutch was engaged. However, using a probe I was able to isolate the noise to the accumulator. Additionally, if the a/c has been off for an extended period of time (a couple of days) there is a loud thud at the accumulator when the a/c is first turned on. If you place your hand on the accumulator when the a/c is first turned on you can feel a small explosion inside the accumulator. I don’t understand how the noise is being generated since there are no moving parts in the accumulator unless the flow path of the freon is being severely restricted by some internal component failure. Questions: Is it possible for an internal failure of the accumulator to restrict the flow of freon enough to cause B-1347 to set on a fully charged system? Was there a TSB published regarding accumulator failures in the 99 Deville? GM has replaced the original accumulator (P/N 1132695) with a new part (P/N 88968517). Was this because of a higher-than-normal failure rate of the original accumulator? Link to comment Share on other sites More sharing options...
Ranger Posted March 23, 2006 Report Share Posted March 23, 2006 RGH, As I told you when I sent you here, Kevin (KHE) is the A/C guy here but as you may have noticed from his post, he is in WV picking up his ebay winnings, so be patient. Link to comment Share on other sites More sharing options...
rgh1016 Posted March 23, 2006 Author Report Share Posted March 23, 2006 RGH, As I told you when I sent you here, Kevin (KHE) is the A/C guy here but as you may have noticed from his post, he is in WV picking up his ebay winnings, so be patient. Thanks Larry. I did notice that Kevin (KEH) appeared to be away at the moment. I will wait. Link to comment Share on other sites More sharing options...
KHE Posted March 25, 2006 Report Share Posted March 25, 2006 An accumulator has only two failure modes - 1) the dessicant bag ruptures (rare) or 2) the deccicant becomes saturated with moisture. If the onboard diagnostics says the car is low on refrigerant, then it IS low on refrigerant. The system is very accurate in that respect. If you are using one of those A/C pressure gages that looks like a tire pressure gage, toss it in the trash where it belongs - you need to monitor both high and low pressures to see the true story. Since the diagnostics indicate the system is low, why not add a can of R-134a and see what the vent temps are??? The only accurate way to asses the charge in the system is to recover the refrigerant, weigh it, and compart the weight to the "full charge" specification. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
rgh1016 Posted March 25, 2006 Author Report Share Posted March 25, 2006 Thanks for your comments Kevin. The system pressures were taken with professional gauges designed for that purpose. The high side pressure was just under 200 psi and the low side pressure was 38 psi. Since the B1347 code is set by the action of a pressure switch on the low pressure line, it is possible for a malfunctioning switch to give a false reading of Low Refrigerant and cause the a/c to shut down even though the system is fully charged. However, none of this explains the very noisy accumulator or the substantial thud that occurs in the accumulator when the system is first turned on. Additionally, I still wonder why GM replaced the original accumulator with a different part (new part number) if the reliability of the original part was not an issue. Link to comment Share on other sites More sharing options...
KHE Posted March 25, 2006 Report Share Posted March 25, 2006 Thanks for your comments Kevin. The system pressures were taken with professional gauges designed for that purpose. The high side pressure was just under 200 psi and the low side pressure was 38 psi. Since the B1347 code is set by the action of a pressure switch on the low pressure line, it is possible for a malfunctioning switch to give a false reading of Low Refrigerant and cause the a/c to shut down even though the system is fully charged. However, none of this explains the very noisy accumulator or the substantial thud that occurs in the accumulator when the system is first turned on. Additionally, I still wonder why GM replaced the original accumulator with a different part (new part number) if the reliability of the original part was not an issue. RGH, What was the ambient temperature and relative humidity when the pressures were taken? 38/200 seems a little low to me. The only real way to determine if the system has the proper amount of refrigerant is to evacuate the system with a recovery machine and weigh the recovered refrigerant. If the weight of the recovered refrigerant is less than the specification (I think these cars take 2.0 lbs. of R-134a) then it is low on refrigerant. It is possible for the sensor to go bad but I think you need to recover the refrigerant in order to replace the switch. If you had a Tech-2, you could check the low and high temp sensors to make sure they are within 2 degrees C from each other after the car sits overnight. There was an issue with liquid refrigerant slugging the compressor momentarily at startup when the vehicle has been sitting for a few hours. There was a liquid bleed hole added to the accumulator - that may be the reason for the design change but I don't think that change applied to all GM accumulators. Part nos. are changed all the time - not just for reliability reasons. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
BodybyFisher Posted March 25, 2006 Report Share Posted March 25, 2006 You can check the pressure switch by temporarily jumping the connector, ONLY if you are sure you have freon. Disconnect the battery, if the code goes away, your switch is probably bad or you have a bad connection at the switch. ONLY DO THIS IF YOU ARE 100% SURE YOU HAVE PRESSURE and ONLY DO IT TEMPORARILY.. Mike Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
mikeal1892 Posted March 26, 2006 Report Share Posted March 26, 2006 I think mine makes noise also. i'm not sure but i also wonder if it is the cooling fans Michael Link to comment Share on other sites More sharing options...
rgh1016 Posted March 30, 2006 Author Report Share Posted March 30, 2006 I had the a/c repaired today and here's what they found: The system was low on freon as the system had rightly detected (B1347). There was only about 0.45 pounds of refrigerant in the system. There was a pressure leak at the high-pressure switch (an internal switch malfunction). Electrically, the switch performed properly therefore it never set a fault code. Even though the low side pressure was about 38 psi and the high side pressure was about 205 psi, the system was undercharged. So, any pressure-reading device that indicates full-charge based strictly on a low-side pressure reading alone may not provide an accurate assessment of the real condition. The noise at the accumulator disappeared when the system was fully charged. The reason why the accumulator was noisy with a low-charge was not determined. Output air temperature from the evaporator is now proper. Link to comment Share on other sites More sharing options...
Ranger Posted March 30, 2006 Report Share Posted March 30, 2006 How did the pressures stay at normal if the freon was practicaly depleted? Link to comment Share on other sites More sharing options...
KHE Posted March 30, 2006 Report Share Posted March 30, 2006 Glad you got it fixed. I figured the system was low on refrigerant. Pressures are OK for diagnosing but the most accurate method is to revover the charge and weigh it. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
KevinW Posted March 30, 2006 Report Share Posted March 30, 2006 The change in part number might be related to a change of supplier or part update (different dessicant technology). I've also observed the 'pop' on initial start-up with some accumulators, and believe it may be exacerbated when ambient conditions cause a higher than normal amount of liquid refrigerant to migrate to the accumulator; the noise is a result of the sudden evaporation of refrigerant as low-side pressure decreases rapidly. How did the pressures stay at normal if the freon was practicaly depleted? High-side pressure is more dependent on high-side temperature than refrigerant charge level. Within some ranges, high-side pressure (along with compressor and discharge temperature) may actually decrease with increasing charge level, due to reduced superheat. If one is able to place a fair load on the system, assessing the state of charge by comparing the evaporator inlet and outlet temperatures is quite reliable. Kevin ___________________________________________________ Link to comment Share on other sites More sharing options...
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