Technical Fiat 500 voltage problems

[Mikefraser93]

Hello, my fiat has the stop/start but 9 times out of 10 it says its unavailable. I have a voltmeter that plugs into the cigarette lighter and voltage ranges from 12.2v all way up 14.2v but it has a new battery and a new alternator. Not sure if I could be an issue with the s/s terminal that connects to the battery reading voltages wrong? Any advice will be great please

 

[the green vanper]

Hello,

Start/stop vehicles should have an EFB of AGM battery. Is the battery type and parameters correct?

Have you tried connecting MES? There could be some errors indicating the cause.

 

[Mikefraser93]

It has a S/s battery. I haven't got mes and no one near where I live has it either unfortunately.

 

[Mikefraser93]

I've also been and had the battery tested and it's perfect

 

[vexorg]

Is the 12.2v when it's running?
A lot of cars have "smart" alternators, meaning they turn off some times is more engine power is needed or some eco-warrior shouts too loud as you drive past.
Some stop-start dont even use the battery now, they have large mega capacitors to kick the starter. Not sure what fiat use.

 

[s130]

Is it just not working or are you getting a "Start/Stop Unavailable" message on the dash?

The Start/Stop system is very complicated and over 30 items are involved in the system.

There is one trick you can try which will initially fool the system to working again and that is to disconnect the two wire connector on the battery negative terminal charge sensor.

Leave disconnected for 5 mins then reconnect and start the car. You may find the S/S resumes but it will stop again. This test will prove the basic sustem is working and the car thinks the battery charge is possibly not good enough.

There are many factors that can stop the S/S working. Some include:

When the device is operating, due to comfort, emission control and safety reasons, the engine may
not stop in some conditions, among which:
Engine still cold.
Battery not sufficiently charged.
Windscreen wiper at max. speed.
Particulate trap regeneration in progress (only for diesel engines).
Driver's door not shut.
Driver's seat belt not fastened.
Reverse engaged (for example parking operation).
With automatic climate control, if a suitable level of thermal comfort has not yet been
reached.
4WD low Active.
Heated windscreen active.

 

[Mikefraser93]

Is it just not working or are you getting a "Start/Stop Unavailable" message on the dash?

The Start/Stop system is very complicated and over 30 items are involved in the system.

There is one trick you can try which will initially fool the system to working again and that is to disconnect the two wire connector on the battery negative terminal charge sensor.

Leave disconnected for 5 mins then reconnect and start the car. You may find the S/S resumes but it will stop again. This test will prove the basic sustem is working and the car thinks the battery charge is possibly not good enough.

There are many factors that can stop the S/S working. Some include:

When the device is operating, due to comfort, emission control and safety reasons, the engine may
not stop in some conditions, among which:
Engine still cold.
Battery not sufficiently charged.
Windscreen wiper at max. speed.
Particulate trap regeneration in progress (only for diesel engines).
Driver's door not shut.
Driver's seat belt not fastened.
Reverse engaged (for example parking operation).
With automatic climate control, if a suitable level of thermal comfort has not yet been
reached.
4WD low Active.
Heated windscreen active.

Hello thank you for your reply. My battery terminal doesn't look like that it goes from negative post to to a quick release post. It does work when voltmeter says above 13.8v. I just don't understand why the voltage fluctuates so much

 

[vexorg]

I just don't understand why the voltage fluctuates so much

Does it change only on the usb thing? or on the battery also?

 

[steveras57]

I've also been and had the battery tested and it's perfect

If you disconnect the wire from the smart battery sensor it should put the warning light on!- if you then re-connect it and it goes out then you know that the system is getting the right readings and voltage!.
The stop start system is over complicated on these cars monitoring far to many parameters!- if even one is slightly outside the expected values then the B.C.M wont let the system work, and flashes up unavailable! can be a right P.I.T.A trying to pin down the problem! thats why most owners turn it off and live with the orange light in the speedo telling em off all the time!

 

[Mikefraser93]

But what I don't understand is why my battery voltage fluctuates so much? I understand the s/s won't work if battery voltage is too low I just don't understand why it fluctuates

 

[Ralf S.]

Is it just not working or are you getting a "Start/Stop Unavailable" message on the dash?

Did we get an answer to this fundamental question?

If you have a "Start/Stop Unavailable" message on the dash, that's a different problem to the S/S just not cutting out the engine out, so we need to know which one it is.


Ralf S.

 

[vexorg]

But what I don't understand is why my battery voltage fluctuates so much? I understand the s/s won't work if battery voltage is too low I just don't understand why it fluctuates

If you'd answer the questions then we might find out

 

[Mikefraser93]

When the voltage is reading above 13.8 it works but when it goes below that it doesn't. Sorry I didn't see that question

 

[Ralf S.]

Do you get a message saying it's unavailable, or does the S&S just not operate?

Anyhow.. check that your S&S is not de-activated on the dashboard. If it's "off" then you will get the "Unavailable" message and the "S" logo with the line through it on the dashboard. If it's "on" then you should not see the "Unavailable" message unless something is wrong and the car has deactivated it..

You need to test the battery voltage (static and with the engine running) and hopefully tell us you're seeing 12.3v and 14,5v respectively... but test the battery directly, not via the cigarette lighter. If the battery and alternator look good (you're getting the voltages above) then the problem might be the condition sensor on the battery terminal. The quick detach post is designed so that anyone charging the battery or jump starting it, can use that (to not put the voltage through the sensor, which can kill it)... but someone might have charged/jumped the car through the sensor and burnt it.

Failing all that, are you sure the alternator is good? If the voltage is fluctuating at the battery when the engine is running then that might be a dodgy regulator. Put all the lights and the rear window de-mister on and rev the engine a bit.. if the lights get brighter, that could be a duff regulator.


Ralf S.

 

[steveras57]

Do you get a message saying it's unavailable, or does the S&S just not operate?

Anyhow.. check that your S&S is not de-activated on the dashboard. If it's "off" then you will get the "Unavailable" message and the "S" logo with the line through it on the dashboard. If it's "on" then you should not see the "Unavailable" message unless something is wrong and the car has deactivated it..

You need to test the battery voltage (static and with the engine running) and hopefully tell us you're seeing 12.3v and 14,5v respectively... but test the battery directly, not via the cigarette lighter. If the battery and alternator look good (you're getting the voltages above) then the problem might be the condition sensor on the battery terminal. The quick detach post is designed so that anyone charging the battery or jump starting it, can use that (to not put the voltage through the sensor, which can kill it)... but someone might have charged/jumped the car through the sensor and burnt it.

Failing all that, are you sure the alternator is good? If the voltage is fluctuating at the battery when the engine is running then that might be a dodgy regulator. Put all the lights and the rear window de-mister on and rev the engine a bit.. if the lights get brighter, that could be a duff regulator.


Ralf S.

all good advice!

 

[Mikefraser93]

It says the message not available I can turn it off like you said and I get the s logo on the dashboard. I will check the battery voltage with a multi meter and let you know. As for the dimming lights I don't get that I had already checked for that myself. Thank you