Ok so driving today and accelerate up then speedo drops to zero, then when i slow down it picks up again and then works fine for miles at 70, then on the way back was working then not working, always seemed to pick up again when i slowed for roundabouts etc then when i hit 4Krpm on the way out seemed to die and show zero again.

I'm assuming the Bravo HGT 155, uses a speed sender unit rather than a cable, i cant find my Haynes manual at the moment and am just in the door from the meet, so anyone got any suggestions on what to check etc.

Initially i'd thought it would have been a loose connection, but with it picking up when i slow down etc i dont know. Today is the first time this has ever happened.

Ok so quoting some info from previous posts:

jug said:

if its intermittent it definately wont be the sender unit at fault, it could be a wiring problem going to the instrument panel, but it will more likely be a dry joint in the instrument panel itself. its a common problem, i wish i knew exactly which joint always causes the problem because a quick touch with a soldering iron would fix it. since its intermittent it means the solder on the joint is probably cracked, but thats very very very hard to spot by eye unless you can follow the circuit for the speedo all along the pcb checking each joint as you go, there are wiring diagrams in the fiat manuals but not detailed pcb maps. if you like microelectronics get stuck in and see what you can find.

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And this thread:
https://www.fiatforum.com/bravo-technical/86206-speedo-problems.html?p=940437

Specifically this bit:

jug said:

well done reading the other threads before posting
what a refreshing change!!

as you said, if its only the speedo that isnt working id attack this problem from the gearbox end first.

theres a good guide on fiatboo describing the repair procedure for the instrument panel if replacing the sender unit fails to cure the problem.

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Seem to conflict

At the moment all the rest of the clocks work fine.

Hi MM!

I would not want to scare you too much but in my case it was the very first symptom of a diff failure. Since the retaining plate on the diff's shaft broke, the shaft slid out a bit from the errr... cage and "ate" the speed sensor's plastic worm to begin with, gradually machining a hole in the box's chassis (but this took a long time).

Diagnosed at an early stage does not harm a lot. Left like in my case destroys the box.

But this may very well be a loose connection at any of the sides of the sender cable.

Ok so doing a bit more digging, it seems that the speed sender unit is the same across the Bravo/a range. Have dug out the eper diag:





How do you change the speed sensor, i read in another post about the chance of something falling into the gearbox, i dont like the sound of that! I have a Brava 80sx outside, would it be worth using the one of that to see if it would work?

What can actually fall in is a part of the 21220 assembly on the second pic i.e. the white worm - if broken or loose. I don't see the reason though why it would fall in if you are careful removing the whole sender unit, it is in good shape and you hold the pieces together.

And if it is worn - you'll have to disassemble the box anyway - to fix the reason.

Sorry for not having the pics - I threw my old sender away.

mountainmachine said:

Seem to conflict

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looking at all the past issues, i tend to think of it this way- a constant fault only on the speedo would suggest the speed sender unit is not working, an intermittent fault only the speedo would suggest an internal fault in the intrument panel, an intermittent fault on all gauges would suggest a wiring connnector fault on the intruement panel.

obviously this is not set in stone, an intermittent fault such as yours could just as easily be a lose or dirty connector on the speed sender unit, or a wiring connector on the intrument panel.

its best to use the fist banging method to determine what the actual problem is. if a good thump on the dash has an effect, you know 100% your problem cant have anything to do with the speed sender unit or its connector and wiring. if the fist banging works it can only be an internal instrument panel fault or one of the connectors on the back of the instrument panel.

Mine was initially intermittent even though it was the sender worm being worn. But loose cables are easier to check!

Yup well i'll be getting some more electrical contact cleaner either today or tomorrow, so will take the dash etc out and check connections, giving it a bang didnt seem to help yesterday, is it worth changing the speed sender unit with a 2nd hand part to rule it out? As i have my old Brava sitting outside, and have no time to do anything to her as of yet. So could borrow the part from her.

mountainmachine said:

is it worth changing the speed sender unit with a 2nd hand part to rule it out?

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definately

jug said:

definately

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Cool i'll get under the car and get the old one off, is there anything is should watch when doing it? As in the whole thing about stuff dropping into the gear box etc, am slightly worried about that, but is that only if i'm replacing the unit inside the gearbox?

i've never experienced the bits dropping off phenomena myself.

jug said:

i've never experienced the bits dropping off phenomena myself.

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No probs.

Sender unit.

Had the same on myn. Left it and left it as i was scared of the pinion droping into the gear box like the haynes manual said. Even had an Ex-Fiat mechanic out to it, but it decided to work so he could not fault it.

In the end the speedo died and the mileage stopped working, so had to change it.

Done it myself, and nothing dropped off.

Cool well i'll get at it soon as i can.

Hi stripped down the battery tray and having trouble identifying the sensor on my Brava 80sx i thought it was on the top but there are a few things that look like it could be them. Anyone got any tips.

look in the manual and you'll find the answer to most questions

Just thought id ask where can i locate this manual that you keep posting on threads. Looks handy :yum:

http://www.babarmalik.com/ledmods.htm

there are 4 PDF manuals to download in total. it takes a while to get used to using them, but once you've got the hang of it they're very useful.

jug said:

look in the manual and you'll find the answer to most questions

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haha its finding the page in the manual thats the problem, got my haynes back today, so found it ok, i think. My mates brakes had seized so spent the day stripping the callipers down.

mountainmachine said:

haha its finding the page in the manual thats the problem

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:yeahthat:

i'm seriously considering running some ocr software on it to make it text searchable. and make a lot more menu's with buttons. one day when i've got a spare couple of hours i'll get round to it.