Loss of electrical power

Weird. I've had problems which were only evident when the car was hot, but I wouldn't expect a two minute cooldown to fix a problem (and then have the problem stay away for the rest of the drive).

Anyway, do the basics. Check battery voltage (car running and not running). If you've already checked the battery connections, check the alternator connections (for security and contamination).

Some questions for the experts:

Does the inertia switch on a GTA have any affect on the engine and on starter cranking?
Does the immobiliser on the 456GTA stop engine cranking?

Weren't you doing some work on your airconditioning system? Have you disturbed something?

 

May not be any help, but I had an identical problem a few years ago with my Maserati and it was down to a bad earth.

 

Voltage drop to the starter motor activator. Common problem.


Sent from my iPhone using Tapatalk

 

Starter motor activator? What's this? The starter solenoid? The starter relay? What is the common fix?

 

The trigger wire to the solenoid. They get a voltage drop when hot. Let the vehicle cool Down a bit, and the voltage with increase enough to activate the solenoid again. It just needs a relay fitted, but the activator wire is also a ground sense for the ECU, so a dropping resistor needs to be fitted. You can use a ballast resistor, but I’ve used 5w ceramic resistors because they don’t fail.


Sent from my iPhone using Tapatalk

 

But the transmission issue won’t be related to it. That could have just required a stop and restart.


Sent from my iPhone using Tapatalk

 

Thanks, but I don't understand why you would be driving along and the car would go dead (electrically). The starter circuit wouldn't be active at this time. Or is it related to this...

Assuming the 456 is similar to the 550, when you turn the key to START, you are providing battery voltage to the starter solenoid via the starter relay (which is closed by the immobiliser). I don't see what relationship this circuit has to (Motronic?) ECU grounds.

Perhaps I'm assuming too much

 

He didn’t say the car lost power, he said the car wouldn’t shift gear. The non cranking fault when hot is usually a voltage drop issue. It’s a common problem with the 456’s.


Sent from my iPhone using Tapatalk

 

Forgive me for jumping to conclusions

 

I’m not saying you’re jumping to conclusions, but he doesn’t say the car goes dead, it looses power (I’m assuming horse power) and doesn’t change gear. To me that indicated he could still drive the car, but it was gutless and wouldn’t change gear.
I’m only trying to offer some help here. I’m a career Auto Elec, (35 years) with my own company, and we do a lot of work on European vehicles. In any case I hope he gets it sorted.


Sent from my iPhone using Tapatalk

 

Despite being a career (non-automotive) "electrician" myself, and having redrawn both the F355 and F550 wiring diagrams line by line to help with problem diagnosis, I'm still having trouble understanding how the starter circuit would suddenly cause the car to lose power of any kind unless there was a fault with the ignition switch or starter relay. How would adding a load resistor to the starter circuit help if the starter circuit is not even supposed to be active?

At this point, we don't have any useful diagrams for the 456 (at least none which I can relate to) and the 550 diagrams don't always make sense (For example, they show a 4-position ignition switch rather than a 3 position switch)

550 Engine Interface/HVAC wiring

I'm also trying to help. As you know, Adrian lives in a rather remote region of Australia, so he probably needs some very specific instructions to give to his basic auto electrician (or some suggestions for himself such as a simple relay replacement or cleaning of specific earth lugs).

Anyway, looking forward to some feedback from Adrian.

 

I didnt say the starter issue caused the loss of power/shifting issue. I said the non cranking would be a voltage drop to the starter. The shifting issue could have just been a stop/restart cycle requirement. With Ferrari Electrics, as I’m sure you know, they can be very touchy when it comes to voltage drops, especially upon start up, more so if the battery is below par. As for your credentials as an electrician, I don’t question them, but automotive DC is my specialty. I also own a 456GT and have spent innumerable hours working on it, mechanically and obviously electrically. I’ve got a thread on some of the work I’ve done on it in the Aussie section (enter at your own risk! Lol) which is a very small section of what I’ve done on the car.
The starter activator signal also goes to the ECU. The ECU looks for a circuit through the solenoid, so there is a small voltage there at all times. When you fit an aux start relay to bypass the voltage drop to it, the small amount of voltage there is enough to keep the aux relay engaged and will cause the starter motor to run ‘in mesh’ and destroy it. To overcome this, I use a 5 watt resistor (ceramic) as a load resistor for the activator signal, and once the engine has started, the resistor drops the voltage enough to stop the relay being energised and the starter will disengage. This is very common on many European vehicles, especiallly BMW’s, which also have a signal from the ECU to the starter activator, but it (the ecu) uses this circuit to complete some of the internal grounds, and when open circuited, the car barely runs (another tip for the BMW folk).
Anyway, I’m getting RSI from all this typing. I’m also in Australia, and know the car Adrian has bought (Ex Tassie, Ex Pioneer promotional car). If he needs any help, I’m happy to speak to him over the phone. He can PM me if he wants.


Sent from my iPhone using Tapatalk