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A/C Compressor Knocking

trevor88 on Tue July 21, 2015 5:31 PM User is offlineView users profile

Year: 1991
Make: Honda
Model: Accord
Engine Size: 2.2L
Refrigerant Type: R12

Good afternoon, I have a question regarding a new compressor that I installed in my car. I replaced the compressor, dryer, expansion valve, and o-rings. The air is cold, but the compressor is starting to knock. The compressor came with oil in it already, so I didn't add any new oil. However, the knocking is only for the first 10-15 seconds of the car being on and the A/C being on. After that, the noise goes away and it runs with no abnormal sounds. This is only on a cold startup first thing in the day, and doesn't happen anytime while driving with it on. So, I am wondering if anyone could point me towards a probable cause. Thank you for your time.

GM Tech on Tue July 21, 2015 10:05 PM User is offline

Refrigerant migration- causes liquid slugging- refrigerant pools in the compressor on a cool night and must be pumped out on start-up - hence the noise- a design issue that you can't fix.

The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

trevor88 on Tue July 21, 2015 10:39 PM User is offlineView users profile

So is the liquid migration issue going to affect the life of the compressor? Should it be something I could address by any sort of fix?

Cussboy on Tue July 21, 2015 11:41 PM User is offline

I have compressor slugging in my 2005 Yukon to the condition where the separate AC serpentine belt has broken a few times. A new tensioner didn't help, so I have ordered from Rock Auto a Deslugger timer to install when I install my new compressor, yes changing the compressor even though it still cools great at 164K miles. The Internet is full of such GM compressors slugging and continuously breaking belts, from being lower than the rest of the AC system. This product won 2014 MVAC Innovation Award.

They have a deslugger for Honda CRV too.

Edited: Tue July 21, 2015 at 11:42 PM by Cussboy

trevor88 on Tue July 21, 2015 11:53 PM User is offlineView users profile

My Honda is a '91 so I doubt they make a deslugger for it. I'm fine with the initial noise as long as it doesn't damage it or cause more problems. I hate the noise but it is what it is. The system is literally brand new. The shop I took it to wanted to convert it from R12 to R134a at a price tag of $1800 (yeah, right). I thought at first I didn't do something right but it seems that isn't the case.

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