Technical fiat 500 1.2 problem when lights turned on

[Demi 500]

2012 fiat 500 lounge 1.2 petrol manual.
Hello
Issue I'm having is:
car seems to start and run fine and engine ticks over fine until I switch headlights on then the revs start to fluctuate up & down to the point where it almost feels like car is going to cut out also headlights start to dim then return to full brightness.
If I hold revs just above 1000rpms then the issue gets better.
I've changed coilpack plugs & leads & tried to inspect wiring but not found anything out of place.
I did get some engine codes referring to miss fires which is why I did coilpack leads plugs but not sure if the missfire codes appear as part of the above issue ie once lights are turned on and car idle goes mad
any ideas or advice is appreciated thanks

 

[the green vanper]

Hello,

What were the errors read with? MES / AlfaOBD, or a generic reader?

Headlights adds some 120-150W all around to the energy needs. Is the alternator OK? Can you hear any strange noise from the belts, alternator, waterpump?

What is the system voltage on idle with all the electrical equipment off? Does the voltage drop significantly when you turn the headights on?

What happens if you add an extra load to the electrical system? Rear window demister? power windows / mirrors? antifog lights? heated seats? With and without the headlights.

Have you checked / cleaned the battery contacts? How does the engine starts?

 

[John202020]

Does it do the same if you turn on the heated rear screen?

Has the car had a new engine earth strap? If not it needs one and this could be the issue, £5 off Ebay battery out, battery tray out bolt in place, you can use any engine bolt rather than the original if you wish? 8/10mm holes if using a different engine bolt, 300mm long, 25mm2

Battery Lead Power Strap Earth Bond Leisure Cable Leads - 16mm2 - 35mm2 Custom | eBay

Copper conductor with P.V.C insulation, (resistant to oils, petrol, diesel, lubes and a range of diluted acids). All Leads are Crimped for a solid crimp and connection, then protected in the correct colour heat shrink to match the cable colour.

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[Demi 500]

Hello
Codes were read usig a snap on diag tool.
No strange noises .
Rpm 700 no load
drops to 640ish & Up again under load

Battery Voltage 12.56 before start up
14.10 to 14.20ish no load at 700rpm.
but fluctuate between 13.00 to 14.16 under load
Under load ie lights, blower, stereo rear demister everything I could turn on
Lowest voltage was 12.56v at start up
Highest was 14.56

 

[Demi 500]

Forgot to say yes cleaned terminals and car starts 1st turn of key even after days without use
Also I'll order new earth strap see if that does trick
thanks

 

[the green vanper]

I have no idea what charging voltages are normal on these engines, but standard charging voltage should be around 14,4 V. Battery voltage 12,56 V is almost perfect.

If the problem wouldn't be resolved by changing the earth strap, I'd check the voltage regulator.

 

[Demi 500]

I have no idea what charging voltages are normal on these engines, but standard charging voltage should be around 14,4 V. Battery voltage 12,56 V is almost perfect.

If the problem wouldn't be resolved by changing the earth strap, I'd check the voltage regulator.

Cheers ill try strap n try get voltage regulator checked

 

[Demi 500]

Hello again, more help needed please ,
Ive changed the earth strap, gave earth points and battery contacts a good clean. Car starts up on the button as usual but after leaving it ticking over for a while the engine started running/ticking over really lumpy. engine light came on and threw the following codes up :
1, c1221-86 ecm signal invalid
2, U0001-88 c can bus -bus off
3, P0204-12 injector 4 command-circuit. short to battery.
Any advice much appreciated thanks.

Am I right in thinking injector 4 is gearbox/passenger side of engine ?and could this need replacing or is it more likely to be wire issues or something else?

 

[steveras57]

Hello again, more help needed please ,
Ive changed the earth strap, gave earth points and battery contacts a good clean. Car starts up on the button as usual but after leaving it ticking over for a while the engine started running/ticking over really lumpy. engine light came on and threw the following codes up :
1, c1221-86 ecm signal invalid
2, U0001-88 c can bus -bus off
3, P0204-12 injector 4 command-circuit. short to battery.
Any advice much appreciated thanks.

Am I right in thinking injector 4 is gearbox/passenger side of engine ?and could this need replacing or is it more likely to be wire issues or something else?

Looks more complicated than we first thought! sorry but i am no electrics expert can just work through the basics,hopefully someone more knowledgeable will respond soon for you!