Technical Airbag warning after flat battery...

[zippeyrude]

I've experienced a flat battery twice in 3 weeks.

After the first flat battery I changed it with another battery.

After failing to jump start it with one of those portable booster packs (I think mine is bad, I charged the battery for a few minutes and it started.

So I need to find if I have a parasitic drain. Thing is, it started fine the previous evening, fast turning off the engine etc.

Anyway, now I have an airbag warning light.

Anyone else experience this?

 

[koalar]

Nope

Not all safety errors will self clear

The first step is to read the code, it can not be read with generic engine obd

I will probably just need reseting

You need to chase down the battery going flat first, there's no point in fixing the airbag for it to happen again

Are you sure it's charging properly

Do you have a meter that can measure amps

 

[zippeyrude]

Ill check charge and the earth strap. I would have assumed the battery light would come on if alternator wasn't charging?

Nope

Not all safety errors will self clear

The first step is to read the code, it can not be read with generic engine obd

I will probably just need reseting

You need to chase down the battery going flat first, there's no point in fixing the airbag for it to happen again

Are you sure it's charging properly

Do you have a meter that can measure amps

 

[koalar]

Ill check charge and the earth strap. I would have assumed the battery light would come on if alternator wasn't charging?

No the light will not come on until the battery is very dead

The body computer detects a fault in the D+

By it must be below 4.5V at ignition on
And above 4.5V with the engine turning

And that's it

The rest of the time its used by the body computer to adjust amount of charge

The only way to check the earth leads is via a voltage drop under load

If there is a parasitic I can walk you through diagnosing it, it sounds unlikely as they are usally very consistent

 

[GettinBetter]

By it must be below 4.5V at ignition on
And above 4.5V with the engine turning

Where did you get this info, I'm not questioning the validity of it. As an electronics engineer I'm just curious/interested.

 

[koalar]

Where did you get this info, I'm not questioning the validity of it. As an electronics engineer I'm just curious/interested.

From fiat

It's been that way on most cars with a single control cable for the last 30 years

Suzuki splash for instance the battery charge light does not come on until the battery is completly flat

 

[GettinBetter]

Thank you for that
My logic say that that only signifies that the belt is either not on or not doing it's job. So either that's all the dash warning lamp does, or other internal calcs are used to to determine alternator output failure.

It may be why I didn't get a dash warning when my battery kept going flat? Anyway it's all interesting, piecing all the bits together.