I´ve got a weird charging problem on my Bravo 1,6MJT MY11.

Background:
The voltage would vary from 11.3 to 15.2v causing the LED light in the interior pulsate. Spoke to a starter/alternator specialist
that said it would most likely be rectifier or regulator malfunction.
Bought a used alternator from the scrap yard and had a independent workshop change it, took 12h to replace so don´t try this at home!
The workshop called and said the "new" alternator "kind of" worked and suggested to buy a new one and spend additional 6-8h of labor.
A brought the car home.

Problem:
The voltage, when the car is cold, is as low as 11.3v. The alternator is charging ~50Amps @ idle (looks right if I check alternator output vs. RPM).
When the car reaches operating temp the voltage kicks back to 14.3v and all is fine.

Found out that my car is equipped with PTC and it kicks in in three stages when the car is cold 250/500/750w, see diagram.




If I´m not mistaking the current when cold could be as high as ~63AMP´s for PTC + all accessories e.g. fan, light, rear heater etc.
This current together would be higher then the rated 120AMP´s the alternator can produce. At idle with just the running lights it draws ~20-30AMP´s

Would it be normal for Fiat to allow voltage drops to keep the PTC going on cold days, it´s seems like that if I look at the diagram?
I normally don´t drive short distance but if I would the battery would be week very fast.

I´m thinking to take a part, or change, the regulator if this could be the problem with the used alternator. It´s a very tight fit and don´t want to do it if it´s not necessary.

Checked already:
Cable connections, new battery and fuses.
Current and voltage checked with instruments.

Any thoughts :worship:

Hi, just trying to understand your post, therefore a few questions;

How cold are we talking here, like 0 degrees Celsius or -25?
You say the battery reads 11.3v when the car is idling and the engine is cold?
At how many RPM does it idle in this cold state with 11.3v?
Do the RPM increase when the engine reaches operating temps?
What kind of (new) battery do you have installed?
Does the crank pully of the alternator move freely?
What kind of engine oil do you use, like brand and type?
How much volts does the battery show when the car is off, before you cold start?
What interior LEDs are you referring to, factory or custom?

@orndal

may have an update..as 2 months have passed


12hours labour.. thats crazy

Late update, I took the easy way out and removed the two fuses for the PTC heater. Now I have a steady 14,2-14,4V except when on idle (12,8-13,2V).
The alternator won’t put out more than ~50A so it needs replacing but not right now.
Can see a voltage drop if I turn on the rear defroster a cold day but it’s not dropping below 12,8V.
If I get around changing the alternator I’ll buy a new one ?