I was also helped out much by that post, turning the screw counter-clockwise will increase the speed, but be careful, I found with mine slight turns can make significant changes in the speed. It took me a couple of time of trial and error to get it close enough to where I was happy. I didn't however hot glue it into place, which I regret now, because shortly thereafter I must have hit a bump or something and it started reading under again.

 

Can u post link to john m's write up? Have a similar issue in a s3 Q... Been searching for post, but haven't found it yet...

 

Here you go

good luck,

Vin

 

unexpected hiccup

so, in preparation of finding John M's post, I decided to take the spider out and drive past a local speed indicator (one of those signs that will measure and show your speed as you approach) in order to gauge the difference from my actual speed and what the speedo was displaying.

however, in a classic alfa turn of events, my speedo needle was fixated at 20 mph on this trip. no more no less whether I was at a stand still or jetting along at 3k rpm in fourth gear.

so I guess I need to rewind and start with basics of the mechanics of the speedo from engine to cluster.

not use to working on spiders, and I have been spoiler with some of the more modern features and benefit of 24v 164 shop manuals.

if someone. could point me toward s3 spider 101 or to other helpful introductory threads on this topic, thank you in advance!

 

however, in a classic alfa turn of events, my speedo needle was fixated at 20 mph on this trip. no more no less whether I was at a stand still or jetting along at 3k rpm in fourth gear.

speedo only, or, tripmeter/odometer also not working?

could it be that it is pegged at 16mph, not 20mph ? The speedo needle rests on a small pin at 16mph/20kph so will not fall below:
http://www.alfabb.com/bb/forums/24356-post8.html

If indeed it is resting on the pin, then I'd say your speedo is not working. Check fuses #7 and #8 (fuses numbered from left to right)

If not fuse, check speedo cable (speedo cable runs from gearbox to PG/Pulse Generator, from PG there are 3 wires to speedo head...see diagram)....unscrew cable at PG and see if inner cable spins when car is in gear (you could jack up car at rear - !!!remember safety first!! - both wheels off the ground and run engine in gear so the wheels turn)..........or if it turns with your fingers, or pulls out easily, that would also mean it is broken.

If speedo cable is good, then check 3-wire plug that comes off the PG for clean/good connection (near brake booster)

If all the above if fine, then check the PG itself....normally you'd use an oscilloscope, but a voltmeter set to AC volts should probably pick up some pulsing off the "grey" wire in 3-wire plug, or you could fabricate a LED/resistor as in an alfa TSB (it is somewhere on here, but I cannot find it again, it used a simple LED and inline resistor from Radio Shack)

 

or you could fabricate a LED/resistor as in an alfa TSB (it is somewhere on here, but I cannot find it again, it used a simple LED and inline resistor from Radio Shack)

I posted it again here the other day:
http://www.alfabb.com/bb/forums/spider-1966-up/210714-s3speedo-problem-2.html

 

The speedo has a pin at 20mph that it rests on, so it never goes below it. On my spider it was stuck there until I followed the speedo cable down and found that the mid section was leaning on the exhaust, and had total separated and melted the cable. Problem was solved with a new speedo cable.

 

Its just the Speedo not working... This car is pegged at 16 mph...

Today the Speedo would pass 20 mph. I hit about 30 mph at about 3500 rpm in 3rd gear.

Started inspecting the cable and noticed the plastic coating is broken on the area where there is a little holder below brake master cylinder.

Next step is disconnect cable at pulse box and see if it will turn, unless one would think its a calibration issue since the Speedo needle is moving...

I guess my question is, should I rule out the cable since the Speedo needle moves?

Please advise

Thank you!

 

as the odometer is working and the speedo needle does in fact move slightly, I'd guess it was the speedo head itself (the pot.)
But, I'd also inspect speedo cable. A dirty/frayed speedo inner cable....or a sharp bend in it somewhere....could also be where the speedo cable fits into the gearbox has come loose....or either of the square cable ends has rounded off so not spinning as fast as it should.

My 'guess' would be that the IG would either work or not work....it is just a hall sensor.

you should be able to remove speedo cable at IG and pull out the inner and inspect it.

 

Speedo Success?

Thought I would update everyone on my efforts to fix my Speedo. Just to refresh everyone's memory I followed the instructions in John M's great post to adjust the pot on my Speedo which was registering before, but was very very low. Would barely get above 30 MPH at highway speeds. When I put the cluster back in my Speedo was registering (hallelujah) but was reading about 10 MPH low (bummer). Took the cluster back out and turned the pot counterclockwise from about the 10:00 position to about the 9:00 position. Put the cluster back in and looks like I am still about 2 MPH low which I think is about as good as I will be able to achieve on my own.

Did my testing at 45 MPH following my wife in her car. Not sure how accurate it is at highway speeds but at this point I am still basking in the glory of my success and will leave well enough alone.

Thanks again to John M for his great post. I never would have thought to attempt this until I saw his post. Its not that hard. Only tricky part is getting the speedo and tach back on the connecting posts when you put them back in. Oh, and trying not to lose the 4 screws that mount the cluster to the monopod housing.

 

Congrats!

Vin