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Registered User
Join Date: May 2013
Location: Picton, Ontario
Posts: 26
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Help me diagnose noise behind dash
I've had a rattling noise coming from behind the dash in my '88 3.2 for some time now, and it's getting worse so about time I looked at fixing. I've included a video to demonstrate the noise - here's the rundown...
Car does not need to be running or moving Noise starts as soon as key gets to 'ignition 2' position Seems to be coming from directly behind HVAC control panel Pushing on panel will slightly alleviate the intensity When driving, cornering has an affect on intensity as well - sound lessens under hard cornering I've removed the ashtray - no change https://www.youtube.com/watch?v=SXbyMJlQQmE Does anyone know if there's a small fan/blower behind the panel that runs all the time that could be giving me trouble? Again, car does not need to be running, and noise happens with all HVAC controls off. Just looking for insight before I start tearing things apart.
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1988 JDM Carrera 3.2, cat delete, Fabspeed exhaust, Euromeister replicas (Fuchs in the garage). LOVE IT! |
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Registered
Join Date: Aug 2008
Location: sectors R&N, SE Pa
Posts: 3,117
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Hi - your video is setup as private.
Yes, there is a fresh air blower in the area. Open the trunk lid and listen for it behind the black hardboard under the windshield. See if you can hear it there as well. I forget what switch turns it off :-)
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Dan '87 Targa Carrera 3.2 - Fabspeed Cat Bypass, M&K Muffler, SW Chip Venetian Blue Last edited by steely; 09-21-2014 at 08:09 AM.. |
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Do you have auto heat? There is a sensor under the ashtray, behind the center console that has a little fan associated with it. On my '87 the fan turns on at position 2 and you can definitely hear it.
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1987 911 Carrera coupe - Guards Red 2010 997.2 C4S 6-Speed 2005 Mini Cooper Convertible (R52) - Wife's car 1977 VW Bay Window Camper Bus |
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Troll Hunter
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Time to open the frunk and start the listening diagnosis. At the very least you should take the carpet out, and then the cardboard at the back. A flash light and some feeling around in there should located that noise pretty quickly. I'm guessing Fresh Air blower...
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1978 SC Coupe, Gris Argent Metallic Silver 1988 FJ62 Blue/Gray 2020 M2 CS |
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Join Date: Jul 2013
Location: Munich
Posts: 266
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I bet it is the temperature sensor
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Registered User
Join Date: May 2013
Location: Picton, Ontario
Posts: 26
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Thanks for the replies, everyone! The noob has fixed the link :roll eyes:
I'm pretty sure it's not the fresh air blower, because that's what's activated by the top, right hand lever, correct? I have ensured that nothing is turned on, and I can clearly hear when I turn on that blower. I do have auto heat, so if there's a fan attached to that, I'm betting that's it - my brother had this problem in an early 90's BMW as well. Do you know if you can access that sensor from the frunk? Cheers!
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1988 JDM Carrera 3.2, cat delete, Fabspeed exhaust, Euromeister replicas (Fuchs in the garage). LOVE IT! |
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Registered
Join Date: Aug 2008
Location: sectors R&N, SE Pa
Posts: 3,117
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Sorry, took a football / tv break. Yes, the fresh air blower is activated. I am not sure that the sensor would be causing the noise unless it was rattling around. You might be able to access it from under the dash if not the little vent plug itself behind the steering wheel just to the left of the heater controls on the dash. I am attaching a very nice figure from Ian McArthur from some time ago.
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Dan '87 Targa Carrera 3.2 - Fabspeed Cat Bypass, M&K Muffler, SW Chip Venetian Blue |
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Great pictorial of the HVAC system Dan, thanks for sharing/posting it.
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1986 Targa Guards Red 2021 MT09 SP |
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The sensor is not in the frunk. It's in the cabin under the dashboard. The easiest way to find it is to follow the black tube that runs from the round vent to the right of the steering wheel and to the left of the HVAC controls. The tube attaches to the back of this round vent and runs down to the sensor.
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1987 911 Carrera coupe - Guards Red 2010 997.2 C4S 6-Speed 2005 Mini Cooper Convertible (R52) - Wife's car 1977 VW Bay Window Camper Bus |
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For pictures, check out this thread.
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1987 911 Carrera coupe - Guards Red 2010 997.2 C4S 6-Speed 2005 Mini Cooper Convertible (R52) - Wife's car 1977 VW Bay Window Camper Bus |
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Registered
Join Date: Aug 2008
Location: sectors R&N, SE Pa
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I listened to the video - that is odd. I can't tell what type of head unit / radio that was - does it have a cassette tape player in it? It sounded like a capstan going bad.
I can't tell if it was related to the air blower or not either, like a leave trapped in the fan. Hopefully someone else can listen. As mentioned before, see if you can hear it in the frunk too. Perhaps try removing one of the instruments (clock maybe) to see if that gives you a clearer path to the noise - check first on how to do this - sorry I can't recommend the exact method.
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Dan '87 Targa Carrera 3.2 - Fabspeed Cat Bypass, M&K Muffler, SW Chip Venetian Blue |
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911 enthusiast
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Seconded on the Autoheat sensor. Sounds exactly like mine used to. It's held in place behind the ashtray with two tiny Phillips screws. You don't have to unscrew it to disconnect the plastic block of a wiring harness that powers it. Try pulling the electrical connection and see if that solves the mystery.
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Registered
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I just watched your video. Sounds exactly like my car. That's got to be the auto heat sensor, the little fan associated with it.
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1987 911 Carrera coupe - Guards Red 2010 997.2 C4S 6-Speed 2005 Mini Cooper Convertible (R52) - Wife's car 1977 VW Bay Window Camper Bus |
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Join Date: Jul 2007
Location: Calgary, Canada
Posts: 293
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Hey, my car have the same noise. Have you diagnosed the problem yet? Subscribed!
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1981 black 930 with full 1st gen Gemballa bumpers kit. RUF classic wheels. Modification include: Mode Inc. (Bob Holcombe) full bay intercooler, headers, turbo, and muffler. 360RWHP. |
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Registered User
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Sorry for the bump; I thought this was the correct diagnosis, I had the same sound. I pulled the small fan mounted to the rear of the ashtray which was full of 30 years of crud (see picture). The noise is still there, it seams to get higher in frequency as the revs increase... any thoughts? Last edited by Alister_AU; 05-14-2017 at 11:28 PM.. Reason: Mistaken diagnosis |
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