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73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: Tazman on June 02, 2013, 05:46:30 pm

Title: A/C NOISE
Post by: Tazman on June 02, 2013, 05:46:30 pm

Used the air in my truck today for the first time since last summer . Worked fine till I came to a stop or idled . Then I would hear a loud groaning noise coming from the engine , so I would shut it off when it happened a would start back up when moving again . I have no idea what this would be.Thanks

Title: Re: A/C NOISE
Post by: bd on June 02, 2013, 07:26:23 pm

If you hear the 'groan' only at idle, and the noise goes away when you rev it 100+ RPM, it might be compressor belt vibration.  The R4 (four cylinder) compressor naturally generates four pulses in the belt as it cycles through one complete revolution.  The spacing of the belt pulleys allows a standing wave to develop in the belt at low RPM - essentially, the belt resonates.  The solution - make sure the A/C belt is sufficiently tensioned.

Title: Re: A/C NOISE
Post by: Harmon on June 02, 2013, 10:22:11 pm

I have the same issue.  I was actually going to post about this too.  I will check my belt tomorrow.

Title: Re: A/C NOISE
Post by: 74 C-10 Shorty on June 02, 2013, 10:56:34 pm

I had the same problem in my dually, belt wasn't tight enough..

Title: Re: A/C NOISE
Post by: Tazman on July 11, 2013, 10:44:47 pm

Tightened the belt and the noise is still bad.To warm to do much about it except shut it off when stopped.
Thanks

Title: Re: A/C NOISE
Post by: DrDaryl on July 13, 2013, 03:22:18 pm

R4 compressor may be a bit low of oil; I've also read that they don't circulate oil well at low rpm and tend to "growl".  I put a throttle kicker on mine to bump it up a bit at idle when the compressor is on.

Title: Re: A/C NOISE
Post by: Tazman on July 20, 2013, 03:44:03 pm

Found out that the belt has been stretched so I replaced it this morning.In doing so I found a bolt has been missing,must have vibrated out anyway I replaced it .Started the truck and turned on the air, the missing bolt and the belt combined must have made that noise.Works great now.Thanks