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Discussion Starter #1
Background:

The car had an original speedometer that died and was replaced. Now speedo #2 is dead. I can't imagine that BOTH speedos died, but I guess it is possible. I recently bought the car with a dead speedo and odometer.

Speedo #1 was original. It has brown electrical boards and the needle rests at about 11-12mph.

Speedo #2, part # 60723375, according to its box (previous owner was storing #1 in the box), has green electrical boards and the needle rests at 16-17mph.

Now, in the research that I've done (looking at eBay Spiders for sale), Speedo #2 is a 1991-1994 style speedo.

Question #1: Will a 91-94 speedo work in an 86 car? Apparently it will, as the previous owner put 29k on that speedo until it died.

Question #2: Where should I look next?

It just seems odd to me that it would be the cable, since speedo #1 was successfully replaced, but I guess the cable could have gone out, too. But it's also really odd that TWO speedo/odos would go out in the car.

Any thoughts? :confused:
 

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In the beginning there were fuses. So they should be checked first.

Then, start by checking the pulse generator and the cable between the pulse generator and the tranny. The pulse gen I believe is 3 wires: 12V, Ground, and Signal. The grey is signal. See if the grey wire is giving signal with a multimeter set to tach.

If not getting a signal then check to see if power is getting to the pulse generator. If not getting power to the pulse gen...then recheck fuses. Check the ground as well with multimeter. And make sure that the tranny cable that runs to the pulse gen is not frozen, rounded off, or otherwise not turning the pulse gen. If the power is there, the ground is good, the cable is good...but no signal...then you need to replace the pulse generator.

If getting a signal...then its the speedo head or a fuse. The Speedo rides on soldered pins into the ribbon cable. Make sure those pins are not broken loose from those solder points on the ribbon cable. The Speedo/odo head unit runs off 3 wires/pins.....12V, Ground, Signal.

Hope this helps...

John M
 

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Discussion Starter #3
hey John (and others)...

I solved the problem... and it was a simple one. My first instict was to pull the cluster apart since I wanted to dust it anyway (pardon my compulsiveness, but I think somebody sneezed in it and put it back together.

However, once everything was apart and I confirmed that everything had been plugged in and I was getting power to everything, I popped the hood and looked at the sending unit. I noticed that the speedo cable was just a little loose, so I tightened it... and went for a spin, just to see. It works! I guess it's just THAT sensitive.


I am still a little baffled about the speedos and where the needle should rest.

Here's what I mean:


'91 Automatic:



My old '86 Grad:





I found an ebay '88 with the needle resting around 17, too.
 

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Andrew,

Glad to hear you were able remedy w/out having to send it to Palo Alto. :)

BTW, the speedo needle in my 94 rests in the same spot as your 91.

Regards,
Craig
 

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Discussion Starter #5
Craig LNU said:
Andrew,

Glad to hear you were able remedy w/out having to send it to Palo Alto. :)

BTW, the speedo needle in my 94 rests in the same spot as your 91.

Regards,
Craig

Craig,

My car's actually an '86, but the replacement speedo shows a 1993 manufacture date. Hmmm...

Your 12k miles make me sick. ;)
 

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I checked the speedo and tach on my Spider; the speedo is at 14 and the tach 5. Even sitting still the car pretends its moving.:D
 

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I recall, in the mists of time, reading somewhere that the reason for the needle not resting on the zero position is an Alfa design signature. Apparently it is meant to signify movement or something along those lines. I will check back in my books and see if I can find it again.
 

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Discussion Starter #11
Ren said:
I recall, in the mists of time, reading somewhere that the reason for the needle not resting on the zero position is an Alfa design signature. Apparently it is meant to signify movement or something along those lines. I will check back in my books and see if I can find it again.


Hmm... well, it looksl like Spiders got FASTER the longer they sat still!

It appears that the needle change occured in 86 with the switch to electronic gauges and then again in 87-88, not sure why then.
 

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If you look closely, there are little stopper pins that the speedo and tach rest on when off. I would guess they're inaccurate below those points, hence the stoppers.
 
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