Analogic Sound

Here is a nice post related to one of my cars, Alfa Romeo Crosswagon Q4. I own this car since 4 years, bought it as a second hand vehicle but no generator maintenance/repair was mentioned in the service book, the generator received a new free-wheel pulley last year, mileage is about 200k so as a rule of thumb nasty things would happen at this mileage if we consider “the plastic age” as a fact.

We must say that the generator is badly ventilated in the engine compartment and is affected by heavy thermal stress and the most wrong thing, it is unfused(skunk mind failure), a lot of cars have a maxi-fuse which prevents battery shorts through alternator or undesired grounding of the alternator output(battery failure), rare events that have a huge fire hazard potential, you are a dead man cruising if something like that happens on road and the best thing to do if you hear a whining sound from the engine related or not to a battery symbol and you observe smoke from the engine/alternator is to disconnect the battery as soon as possible and try to save your car or yourself using a fire extinguisher.

Long story short, I survived, car survived, the alternator was analysed, the stator was in bad shape, the rectifier was shot, bearings, regulator, rotor, all good, it’s time for another r&r job, some people would like to use parts from scrapyards but this is not the case for me on a daily driver, I want my electric systems to be very good, reliable and with a well known service history.

Few pictures with the original stator:

The alternator failed because of the damaged rectifier by thermal stress, 4 of 6 diodes were damaged and soon after that, the battery was shorted through alternator’s stator windings burning them, measurements taken after the event showed a short circuit draining 210Amps from the battery with engine off, that is dangerous, extremely dangerous and it is a must to disconnect the battery as soon as possible in case of such event (I am afraid that a lot of people would not be able to do so and they can lose their cars at least), that is why some manufacturers fuse the alternator circuit with a maxi-fuse rated at maximum charging current plus 10%, on Crosswagon Q4 Alfa Romeo the alternator feeds from the starter which is unfused so the alternator is unfused too.

Here is a schematic of the alternator which contains a 3 phase generator, rectifier, regulator, all built in.

I tried to find the schematic of the alternator on the internet but I couldn’t, so here it is, it covers Alfa Romeo diesel 147/156 120A and 140A Denso models, this is also found in Opel Astra diesel models.
It may be a delta(considering it is a high power unit) not a star winding but anyway this doesn’t change the schematic by much.

Voltage regulator is Denso L9106A, solid state, no info on the internet available, but it is very reliable, it just survived a fire :).

Pictures with the disassembly of the free-wheel pulley and other parts:

Few considerations we need to have here, the quality of the old 140A stator is not achieved in the aftermarket replacement, but the goal is to have a rebuilt functional unit as good as it can be, with the lowest cost possible, the replacement stator side by side with the old one, it is rated for 120A, it should be enough for my Q4 as I always keep the electric loads under control, never using a lot of accessories immediately after engine start when the recovery is higher.

The winding of the new stator is a little bit different than the original, using a thick single wire, old one used a double wire winding.

All cleaned parts and new rectifier:

Bearings were in very good shape & good quality, added them some quality grease and everything is ready for assembly:

New stator in:

Now comes a very important part of the project, this makes the difference between a rebuild and a professional rebuild, the way that the rectifier is soldered to the stator wires, terminals are crimped and after that the wires were bent down to ensure a very good mechanical contact and in the end soldering was made with a high power soldering gun:

The brushes were replaced, notice the wear, new vs old brush:

The rebuilt unit:

Charging tests were successful, no charging light was present and the on board voltage is 14.4V, nice and good:

Installation of a maxi fuse rated at 130A will be considered in the near future, more automotive r&r projects will be available soon!