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TINMAN · Joined: 19 Aug 2007 Posts: 78 Location: Baltimore Md

In my 1980 924, the speedometer wont register at any speed whatsoever. has anyone else come across this problem? and were you able to fix it?
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The TINMAN and his TINCAN

"...When she asks... and i know she will...make sure you let her know whos Porsche it is in the driveway..."

80' 924 Burgundy

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2743 Location: Sydney, Australia

It's a mechanical speedo so either your cable has snapped or is not connected or one of the drive gears in the speedo is stripped (less likely). Unscrew the cable at the back of the speedo take it for a drive and see if the cable is turning.
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1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

924RACR · Posted: Sat Sep 01, 2007 10:08 pm Post subject:

It's also possible that it's not engaged at the LF hub - it connects into a square drive in the grease cap, and should be secured by a circlip and sealed with RTV against water. You should be able to see it if you remove the wheel or the center cap.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

D Hook · Joined: 02 Nov 2002 Posts: 3158 Location: Omaha, NE

There's also a mileage counter box on the '80 (well, on US spec. anyway) located deep on the driver's side below the intake manifold that the speedo cable runs to from the front wheel. These are made of plastic and mine broke on the mounting point and broke the collar the cable screws into, letting the cable slip out. You can bypass this by going to a single cable or find a used box, if that's the problem.

The counter box is part of the emmission controls and is what activates the OXY light on your instrument panel when it's time to change the oxygen sensor. There is a reset button on the box to make the light go off.
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'80 924 n/a SOLD

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

I did what D Hook is suggesting with my 1980, when the cable snapped I swapped in the cheaper single cable and eliminated the mileage counter box. I'll just have to remember to change the OXY sensor myself every 30,000 miles

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1987 951 - M193 Version for Japan

TINMAN · Joined: 19 Aug 2007 Posts: 78 Location: Baltimore Md

I looked this up and read about some small gear that frequently got stripped or disconnected in the speedometer or odometer but i thought i was looking at 600 bucks for a new one.... a new speedo i mean

But Ill try checking the cables to see if ones snapped or been disconnected. that should be alot cheaper to replace

Thanks for the help guys. i had no idea about the oxy sensor milage box
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The TINMAN and his TINCAN

"...When she asks... and i know she will...make sure you let her know whos Porsche it is in the driveway..."

80' 924 Burgundy

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

I think the 'small gear' you're refering to only affects the odo counter. Your problem is more likely the cable.
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

TINMAN · Joined: 19 Aug 2007 Posts: 78 Location: Baltimore Md

well... bump for one. thought i had things fixed but i guess not.

it turns out the cable was just disconnected. so after about near pulling the entire dash apart(because the speedo is located above the steering column and i couldnt get to it) i was able to hook it up and hit the highway. but i dont know why but it wont register past 70 mph, and i knooooooooow i was doing more than that. what gives??
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The TINMAN and his TINCAN

"...When she asks... and i know she will...make sure you let her know whos Porsche it is in the driveway..."

80' 924 Burgundy

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Does it read correctly at other speeds or does it always read low? It may be that the speedo gearing isn't correct for your set-up (wheel size, diff ratio, etc).

How fast do you think you were going...? It can be pretty difficult to gauge speeds above about 50 mph just bt 'feel'. What revs were you pulling?
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

Smoothie · Posted: Tue Sep 11, 2007 7:36 pm Post subject:

I'm thinking a heat-related problem with the speedo itself. One of mine does this - the needle goes up to, then sticks at about 35 mph, but only in the heat, when the car's been sitting in the sun. In cooler temps, winter, etc., it works fine. -So yours' may be doing the same thing, but sticking at a higher speed. If so, you should find it works better in cooler temperatures.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

And should worse come to worse, there are certified VDO places that recondition speedos for under a hundred, so you can put that 600 out of your mind.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

Speedo heads come up all the time on EBay - ~£10 (<US$25)
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org

seanski44 · Joined: 13 Mar 2006 Posts: 532 Location: Nottingham UK

also, you could pull the speedo and attach a drill to the input and try it (seem to remember you need the drill in reverse) you should easily get up to 80 by this method, so it might help in checking that the speedo is the prob not the car

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1998 BMW Z3 2.8 arctic silver & red

1981 168HP 931 S2 blue/tan leather - SOLD

1985 121HP 924 2.0l na modded - SOLD!
1992 968 lux SOLD
1989 944 2.7 lux SOLD

Smoothie · Posted: Wed Sep 12, 2007 2:34 am Post subject:

Yes - use a medium-size square-drive bit in the drill and run it in reverse at approx. 1100-1300 rpm. (I used a 700 rpm drill on mine and that drove the speedo at about 48-49 mph.)

-Then if it still sticks at 70, put it in a refrigerator for a while, and then try again.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

...then, build a refigeration plant into your car that comes in at, say, 55 mph so that it's nice and cold by the time you get to 70 and your speedo will work. Easy!

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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org