impulse generator voltage

Hello.

We have been attempting to go through the entire wiring on 46567 to ensure that it lasts through hopefully my lifetime the next time some of the systems go haywire... So, with the speedometer in mind, Michel knows that the input voltage for the impulse generator attached to the transmission is 12V.

However, the million dollar question(s) are: 1) what is the output voltage for the impulse generator when the car is in park; and 2) what is the output voltage when the car is being driven since the wheels are spinning - is there a difference?

He attempted to do his own research on this but did not get anything back that is definitive. Those that have this information, please chime in and very much appreciated.

 

Okay... So, Michel attempted to have a speed shop in Ft. Lauderdale figure out what is going on with the faulty speedometer/odometer. This shop specializes in gauges and we were under the impression that they could source and/or install something generic that would otherwise make mine work properly. In fact, Michel has used them before on 46567 to have all the other gauges work in sync. But, they apparently got stumped with the speedo this time around.

1) They were able to ensure that mine does, indeed, work but 2) apparently, they would not be able to put in an alternative to make things operate as they should.

I performed a search on eBay and Russ from Ferrparts came to the rescue, advising that Part No. 116987 consisting of a new, OEM speed sensor replacement for my 1985 400i would make my speedo work as it should. So, back to the Ft. Lauderdale speed shop my speedo along with the new one (as well as the old sensor) went, but they simply could not wrap their heads over it as to why it wasn't working.

Fast forward a week plus later, and I spoke with Hartmut today at Palo Alto since Michel sent him my speedo along with the new (and old) sensor. He too was able to hook my speedo up to a machine that shows my speedo works, but not the sensor. Hartmut has another speedo from a Mondial (no year listed by its French owner) where they also sent him a new - and used - sensor a few weeks ago, and he has not been able to track down the issue with that one either. Nonetheless, he attempted to resuscitate mine with all 4 Ferrari sensors he has in the shop, to no luck.

So, what he needs (and I would very much like) is someone else to perhaps send him a 400i speedometer to rule out that the new sensor I got from Ferrparts is defective because according to Hartmut, what are the odds that it may have gone bad from sitting around or, simply defective from factory or ? It is very unusual for one speedo not to work with 4 different sensors, albeit 2 of them from a different Ferrari model.

I did a search on the forum about speedometer issues and found this thread from 2008 where they sent it to Palo Alto and it was rectified. The issue here is that my speedo works, but not the sensor and/or???

http://www.ferrarichat.com/forum/365-gt4-2-2-400-412/189432-412-speedometer-tripmeter.html

So, does anyone have a spare that Palo Alto (and I) can borrow for testing purposes, please? I will reimburse anyone's shipping costs associated with same, including: tracking, insurance, as well as signed receipt. My car has been stalled for the past month because this has grown to become a real head scratcher and I do not know what else to do other than to follow Palo Alto's advice in ruling out the new sensor.

Your input, consideration, and help are so very much appreciated in advance!

 

Ewan, you're showing your age, man! Can anyone here believe that stretches back to 31 years ago? Jeez - where has the time flown by?

Very big props to Russ and Ferrparts - they stepped up to the plate big time and sent Hartmut at Palo Alto a second speed sensor to rule out the first one. Fingers crossed and hope to share good news very soon! I need to update 46567's progress! It's looking great, even if it's sitting still!

 

Okay - clearly mechanics and anything to do with electricity in cars will never be my strong suit. So, I'll give it a shot in attempting to explain why progress on my car has stalled and/or been diverted.

Hartmut at Palo Alto was dumbfounded with my speedo and sensors - the old one the car came with when I bought it, as well as the replacement one I bought from Ferrparts. He had someone else's Ferrari speedo at his shop for weeks without answers and I really did not want that to be the case with mine.

I reached out to Russ at Ferrparts once again in the hopes he'd send a 2nd sensor directly to Palo Alto in order to rule out the previous one bought new from him that had remained unused, but also had not allowed my speedo to work properly as expected. Within the day and no questions asked, he sent a second unit in order to rule out the sensors when Hartmut were to do some more exploratory surgery - I cannot describe how well I was treated as a customer by him and the Ferrparts crew.

Turns out, that the second new sensor did not work either! That led Hartmut to determine that one of the 2 circuit boards (actually, a chip in one of them) on my 400i's speedo did not work - the smaller one. Because the chip itself is not available for sale, a new circuit board essentially replaces the old one, and consists of an enclosed small, black plastic enclosure which is wired to the speedo and located outside of it. The placement is deliberately designed to aid in the re-calibration of the speedo.

Fortunately, Hartmut has a source for them in Germany and he ordered a new, replacement one. Upon receiving the new circuit board, all is now well - turns out all 3 sensors work, which allowed me to keep one of the 2 from Ferrparts, and Palo Alto sent them the 2nd new one which was no longer needed. Kudos to Harmut for making it all work as it should!

Now, my speedo is finally on its way back to 46567, although we have several issues pending. Here are the pics!
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