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Registered
Join Date: Oct 2007
Location: East Coast USA - Tysons, VA
Posts: 1,232
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How to test a 1972 911 Tachometer ?
I have a spare (1972 manufacture) 7300 RPM 911S tachometer for my 1972 911T. The tachometer looks perfect, but I don't know if it works. Is there any way to test these things without actually installing them? If so, how do I do it? I'd just like to see if the needle (arm?) sweeps.
If it ends up being dead (no movement of the needle/arm), what could be possible causes and who would be able to repair it (and how do would they do it)? I don't want to start off thinking it won't work, but you never know, and just in case, if it doesn't, I want to know what to do to fix it. FYI, I'm redoing my 2.4 liter engine to either S or E spec (or some combination thereof), which is why I want to eventually install this particular tach--apart from the coolness factor. For my engine rebuild, I have all the parts (Mahle 2.4 S and 2.2 E pistons and cylinders, and original S and E cams with MFI drive, and a 1972 911S 7300 RPM distributor). I wish I could decide which combination of P/Cs and cams I should use for the most fun on a street car so I could sell the extra stuff to someone who needs it. Thanks in advance for any info and advice. Last edited by M491Cabriolet; 09-12-2008 at 03:30 PM.. |
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06-22-2008, 05:03 PM
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Registered
Join Date: Jan 2002
Location: Long Beach CA, the sewer by the sea.
Posts: 37,638
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For testing and repair, you can send it to North Hollywood Speedometer. If you have an early car with the purple/black wire coming off the distributor, you can hook it up at the dash. If your car doesn't run right now, you could put in on friend's car.
I don't know how to bench test it on a DIY basis. |
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06-22-2008, 05:12 PM
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Registered
Join Date: Oct 2007
Location: East Coast USA - Tysons, VA
Posts: 1,232
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Anyone know how to do a DIY benchtest?
Thanks. I'd rather just try to benchtest it on my own before dropping even more cash toward a pro's bottom line. Of course, if this tach does not work, a pro is going to get it. Does anyone know how to test one of these things? What it the voltage that comes from the purple wire? I imagine it increases with revolutions, or pulses somehow. Any ideas? Thanks.
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06-23-2008, 02:59 AM
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Moderator
Join Date: Dec 2001
Posts: 9,569
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11 volt square wave to the /1 input-- search here
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'66 911 #304065 Irischgruen ‘96 993 Carrera 2 Polarsilber '81 R65 Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13) Ex-'88 Carrera (Sold 3/29/02) Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04) Ex-'89 944 Turbo S (Sold 8/21/20) |
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06-23-2008, 07:22 AM
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Registered
Join Date: May 2002
Location: St Louis
Posts: 4,211
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Tach troubleshooting... at a roadblock and need suggestions
Old LorenFB suggests dragging the tach input over a file that has been grounded.
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Rick 88 Cab |
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06-23-2008, 08:07 AM
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