faulty 308 speedometer

I just bought my first Ferrari, a 1978 U.S. Version 308GTB, just last March 2003. When the car was sold to me, the speedometer was working. Then when the 308 was in my possession, the Speedometer just stopped functioning. That's when I noticed that the odometer was stuck with the same mileage that was on it even before I bought the car.

Once, when the car was on neutral and left at idle, the speedometer needle just went up slowly by itself as if it was a tachometer. The needle rose to the 80mph mark then slowly went down to Zero. It has not functioned ever since.

Thinking there was a ground, I had the speedo checked. They didn't find anything wrong with it so they said it might be the speedo sensor. I bought a NEW speedo sensor, to no avail.

My speedo is still as dead as ever !

What should I do ? Buy a new speedometer ?

 

Get a speedometer sensor before you drive it another mile. It's almost certain that's what the problem is. Takes 10-12 minutes to unscrew the old one,screw on the new one. The longer you take to do it, the more harm to your car's value - prospective buyers won't have a clue as to the "real" mileage and then you'll be discounting the car $10K. That's my 2 cents.

 

it is more than likely to be the speedometer sending unit located behind the rear passenger side tire. it is located in the tranny and can be switched out in 10 minutes. my 79' had the same issue. i was able to rebuild mine, but i would just buy a new one and call it good. DO NOT buy from the dealer. they want 3 times what you can buy it for on the internet.

 

Meant to say "speedometer sending unit", not "sensor." Sorry to confuse.

 

Everyone HOPES it's the sender, but the speedo unit often fails.

Palto Alto Speedometer in CA.

 

Okay, thanks guys will check if my "speedometer sending unit" is still in working order, if not, I will just buy a new speedometer.

 

Palo Alto REPAIRS them, keeping your odo correct.

 

My speedo has also decided to quit. Does anyone have a picture of this unit on the car (308). My assumptions (based on the search I did on this site) is to take it off, clean the connectors put it back on and see if that fixes the problem. If it doesn't what can I expect to pay for a new unit?

JP

 

No picture, but you can't miss it.

It's mounted on the right side transcase. It has electrical wires attached to it via a connector and is brass coloured.

It's a common failure, and most likely cleaning the connectors won't do a thing.

Expect to pay $100+ for it.

 

There are a few different versions. One is a little smaller than this one but similar. One is all brass and almost looks like a plug. Also check the wiring coming off and and heading back up towards the front. Thats where I found my problem. A broken wire under one of the retaining clips for the wires.
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Thanks for the pictures. I will try to clean things up this week-end and see if that fixes it.

 

Before replacing the sending unit, you may want to do a quick check on the wire from the sending unit to the speedometer just to make sure the wire is not fried. Do an end-to-end test.

 

Really? In my previous search for 308's and 328's, it was common to see at least one, and sometimes even two replacement speedo senders on the service history...but never saw any speedometer work. I personally, had to have the sender replaced on my 308 at one point, and my current 328 had it replaced a few years ago, by the previous owner. Never had to have any speedometer work.

Now clocks go with GREAT regularity (have had both repaired by PAS). And in the case of the 3.2l motored cars, the 328/Mondials often have the tach break and start reading low (also fixed by PAS, they were very familiar with this defect).

 

My PO of 308 #2 had the speedo repaired, $1K! I was impressed!

Someone took the clock out of one of my cars to put a VDO ammeter in! Thanks buddy!!

Maybe Ferrari UK has 'em.

Good tip on broken wire! I'm gonna check that!

I had that happen in the multi wire cable to an outboard. Drove me crazy 'till we found that. Who'd a thought one wire out of twenty!

 

Just had my '76 308 speedometer repaired in November 2003. It was not the sensor but a failed circuit board inside the speedometer itself.

Cost = $250 plus shipping.

Where:

MOMA
1321 Second St. NW
Abuquerque, NM 87102
505 766-6661

This is a place that dealers and some shops use. It took about two weeks.

Hint:

Be sure to replace all the dash light bulbs, including those in the speedometer, while you have your dash pulled apart.

Good Luck

 

Hey, thanks for that info!

 

$1K for a speedo repair? YIKES! If I spent that on just a speedo repair, Melodie would beat me within an inch of my life, sling a cleaver through my heart, put a bullet in my head and THEN start yelling at me!

 

I told you this guy was straight up! He put new shocks on it last year and put it back in the garage. Felt great on 121, to 128, into Napa!

Maybe his tech got to him a little on the labor, or it was "in with other things" on the ticket. It's not easy to R & R! He even told me there's about 20 miles on the car, that didn't show because of this! (the distance to the repair shop).

His clocks not running but I know he disconnected some things that drained the battery. Get this though, the thread from the factory hang tag was still wrapped around the stem!!!!!!

 

My speedos bad in car #1.

I have to tell em: "You're right officer...I have NO IDEA how fast I'm going!"

 

Speedomoter now works. Thanks for pointing things out to me. It was very dirty and oily. One of the cars dropped some oil at the track when it quit and that along with all of the dust on the track got into the cable. If it continues to work, then all is well and done.

searching through Ferrarichat for details on how to fix sending unit 4 hours
jacking up the rear and taking off the rear wheel of your Ferrari 10 minutes
removing rear wheel panel 10 minutes
locating and cleaning wires to speedo sending unit 10 minutes
Not having to pay your dealer $100/hr to fix sending unit priceless

Thanks for the help
JP

 

Great news. So what exactly was the problem? Dirty connection where the electrical plug is?

 

yes, dust and oil inside the white plasic connectors. At least I hope so as it now is clean and it now works.

 

Hi Folks,

Reviving this thread after 20+ years.

So, both speedometer and odometer stopped working (simultaneously) on my '77 308 GTB and the first thing I checked was the speedometer sender - a relatively old Veglia Borletti unit . I tried cleaning the white terminal connectors as suggested above but no success. I then removed the sender to inspect it and noticed while (carefully) removing it that the center "lead' was not connected to the upper structure of the sender - it remain on the receptacle, on the gear box interface. Without performing an electrical test on the sender, is that observable enough evidence that the sender had failed, due to lack of contact?

Let me know if you get a chance.

Thanks in advance.

 

If you can fix it mechanically, there are some diagrams on dinoplex.org that can assust you in the tedting & repair of the electronics.

http://dinoplex.org/instruments/vegliaspeedosensor/index.html

 

Thanks for the note and link, raemin.

But the fact that the "center" metal lead was not connected to the sender would explain not generating/transferring the output signal required at the speedmeter electronics, correct?

Thanks again.