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Buzzing Noise at HVAC Sliding Knob?
I was wondering what that meant? Sometimes, my HVAC (Heater/AC) Knob when even in the Off Position, you can hear the HVAC Module Buzzing.
What does that mean? No Bees, checked for that already 
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1981 Porsche 928 "Euro" Auto Gunsmoke Metallic Flat - Black Interior 1983 Porsche 928S "US" Auto Light Bronze (Copper) Metallic - Brown Interior **SOLD** 
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05-25-2011, 02:15 PM
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Registered
Join Date: Jul 2010
Location: Porterville, Ca.
Posts: 101
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Relay going bad inside. There is a write up on renlist from dr. bob (I believe) on how to install a heavier relay.
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'73 914 2.0, '84 944 coupe, '87 944 coupe, '90 944s2 cabriolet, '81 928, '86.5 928s, '71 corvette, '84 corvette |
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05-25-2011, 04:20 PM
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928: Serial Enabler
Join Date: Sep 2007
Location: Elkhart, Indiana
Posts: 2,929
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Diaphragm broken.
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84,85,86 928 cars |
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05-25-2011, 07:13 PM
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Thanks guys! So there's a Relay "inside" the Control Head? Also, wouldn't a broken Diaphragm always make noise and not just sometimes?
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1981 Porsche 928 "Euro" Auto Gunsmoke Metallic Flat - Black Interior 1983 Porsche 928S "US" Auto Light Bronze (Copper) Metallic - Brown Interior **SOLD**
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05-26-2011, 04:39 AM
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928: Serial Enabler
Join Date: Sep 2007
Location: Elkhart, Indiana
Posts: 2,929
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I think the relay is the AC engagement relay and its known-undersized. Dr Bob indeed does a good writeup, and others have too.
The diaphragms if broken will indeed flutter semi-randomly for a while til they break more-fully. Sometimes you can find an intermediate position for the sliders that silences it. 83 has a slightly different actuator behind the center grate than 84/5/6. But I think they all use 3 or 4 diaphragms throughout the HVAC system. You can buy them separately. I've got the parts but haven't done the work yet.
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84,85,86 928 cars |
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05-26-2011, 04:49 AM
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jdill
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merlin told me it took 25 yrs to learn how to sing sit back and enjoy it
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79 928 euro -lint green/black leather 5 speed |
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05-26-2011, 02:53 PM
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Registered
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Sniffer Fan -
Hey MPDano, A possible alternative source of the buzzing noise is the console sniffer fan mounted slightly up and to the right of the A/C - Heater control unit. This fan is sometimes called a sniffer because it samples the interior air temp by pulling it past an encapsulated sensing module. The top of the module looks like a circular disk and when removed is about the size of a salt shaker. The interior temperature sensing resistor (inside the sniffer) works in conjunction with the A/C - Heater control slider resistors and the exterior sensing temp resistor found in the left front fender intake duct of the alternator. If you pull the sniffer module out of the console, simply blow it out with a light dose of compressed air and then apply a little WD-40 to the fan. I've seen sniffers successfully revived to work quietly for years.
Good Luck, Michael
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1984 928S - "Miss Purdy" 1987 911SC - "Frau Helga" 1986 930 - "Well Hung" 1975 911 Targa "Blue" Last edited by JK McDonald; 05-26-2011 at 03:28 PM.. |
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05-26-2011, 03:02 PM
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928: Serial Enabler
Join Date: Sep 2007
Location: Elkhart, Indiana
Posts: 2,929
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Must remove console to remove that fan.
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84,85,86 928 cars |
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05-26-2011, 03:20 PM
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kermit
