Speedo malfunction, dead trans

[Ian Evans]

Well as luck would have it the speedo signal disappeared after I had lunch with Robin today. Of course, 2nd gear only as a result (Automatic). No provision to override Alfa's safety program and manually select a more appropriate gear to drive to the service center??? Must I tow this car once again rather than drive 20 miles in 2nd gear?? It seems that the senders have gone the way of the Dodo bird and vanished from the face of the planet. Strange thing is, I just bought a used one to help out an Alfista in the UK who said he couldn't find one there. Sorry Gerry, I may need to use it myself. No previous symptoms, no moisture involved, crawled under the car and verified the sender is still plugged in, unplugged and replugged, tapped side of sender, no change.

Ian

94 LS

[goats]

yes if the speedo sensor signal is lost the ecu for the trans will default to safe mode

I dont think that the issue is a bad speedo senser per se, I suspect wiring or mechanical issue with the sensor-- its a chopper assembly, a little wheel goes around and provides a square wave signal. They are relatively bulletproof in my experience

Check the wiring at the connector and again at the ECU =-=

where are you located??

bob

[Ian Evans]

Fullerton. There was no warning, no indicators. This happened once before when I drove over a carwash that does the underside. Things were OK after drying out, 2 months ago. Then this sudden failure after parking the car and going in for lunch.

[Ian Evans]

If it helps at all in diagnosis, I have no indicator for "ice sport or auto" when I push the switch.

[goats]

The current state is a result of the induced fault-- ie , what we need to solveis the speedo sensor signal === Do you have a service manual? Are you comfortable getting deep into this (will be mech trim and electrical, nothing close tolerance / oily)

If you are handy with "stuff" - and have a manual== you can disconnect the sensor from the harness, and find the other side of the harness- by (admittedly faulty) memory it goes to the Motronic ECU under/behind the radio/AC console -- ring this out with a VOM == after, of course, checking the wire that the speedo sensor plugs into (ie visually examine the connector, trace the wire as far as you can, etc).

One other item that MIGHT be a possibility- if you have any heater core leakage it tends to get the Auto Trans ECU with moisture. Again, removing the pass side tunnel shield and getting in there will probably be needed unless you find it on the sender side===

[Ian Evans]

Thanks, guess it's time to buy batteries for the cheap DVOM in my toolbox.

Ian

[goats]

by disco the battery for a few minutes and see if you can clear the 'safe mode' latch

[Ian Evans]

Quote:

Originally Posted by goats by disco the battery for a few minutes and see if you can clear the 'safe mode' latch

[AlexGS]

I have repaired a speedo sender once by cutting open, digging out some resin, and replacing two small electrolytic capacitors. It was a textbook repair case - a check with a handheld oscilloscope showed a strangely-modified square wave (sloping tops to the pulses, amplitude only 0.7 volts), after replacing those capacitors I had a proper square wave with 5 volts amplitude. I have photos somewhere at home but not here with me at the moment.

-Alex

[Ian Evans]

I'd be interested in seeing the photos if you find them.

Ian

[Ian Evans]

Any joy from hard reset was short-lived. Drove approx 5 miles with everything apparently normal, loud bang from drivetrain and back to no speedometer and 2nd gear only.

Ian

[goats]

The hard reset idea is only to get you to where you can work on it. I would go under the car, and carefully check the wires, connector, etc as completely as you can. You might want to pull the sender but be careful you don;t lose the little gear down insider the transmission=== Steve can tell you how to do it I can;t, never had it out!

I still think the problem is in the wiring not the sender per se

[Alfisto Steve]

Quote:

Originally Posted by Ian Evans Any joy from hard reset was short-lived. Drove approx 5 miles with everything apparently normal, loud bang from drivetrain and back to no speedometer and 2nd gear only. Ian

[Ian Evans]

Quote:

Originally Posted by Alfisto Steve This does not sound good did speedo drop off to zero and then tranny dowshift to second gear and put your chest on steering wheel? How fast were you going jest before it happened. Normal default to second gear if you lose signal from sender to speedo and tranny ECU. Maybe wiring but senders do fail. Myron's 95LS gave him a fit until I found out sender was going bad. Installed new one and never had a problem with tranny since. Alfa Parts in Berkely list one for 164 A/T tranny as 7624313 another Alfa number for same A/T sender is 60800459. It is different than 5-speed models. Somebody just did a buy it now for one on ebay that I was hoping to buy it for my 91L as sender is intermittent but price was to high. At least on 91 speedo error does not down shift tranny like 24v one does.

[Alfisto Steve]

Quote:

Originally Posted by Ian Evans That's what I experienced, but fortunately I was not driving more than about 25-30 at the time. I am the "buy it now" guy, as I have heard these units are no longer available. Yes, the price was high. I wonder why International pulled the listing? Price was still high, but at least available as recently as 2 years ago. I don't put too much stock in Italian component numbering, and am sincerely hoping that this sender is correct. I mean, how complicated could it be? For all intents and purposes it appears to thread on to what is essentially a speedometer cable connection, complete with square cable style socket. Saab uses the 4HP18E trans too, but the sender looks significantly different (#4083804) No idea if it would work, and priced comparably but at least available. Ian