Alfa Romeo Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
86 Posts
Discussion Starter #1
Hello everybody. My 2.2 JTS 159 has developed a problem, where most of the time all lights flicker rhythmically irrespective of the load on the system - faster at low RPM and slower at higher RPM. When there is a load on the electrical system at idle like the radiator fan turning on, the frequency of flickering increases, but at higher RPM the flickering is slower and constant. There are no warnings and the battery voltage engine off is at 12.4 V, when running normal it's around 13.2 V, but when flickering it varies from 12 V to 13.3 V according to my cheapo multi-meter. My mechanic connected a device to check the alternator and he says everything is fine and he can't work out why it's doing this. I can hear a momentary high pitched shriek when the flickering happens from the alternator area- but I can't workout if it's the belt slipping or a bearing problem. The battery is only 8 months old and is in good condition.

When any errors are logged, the voltage in the log is always <10 V and the latest misfire has Air temperature logged at -20° C, but the air temperature sensor reads normal when checked with alfaOBD. Not sure if this is connected to this or not.

Anyone have any ideas or experience with this problem? Just thought I'll ask before spending hundreds on a new alternator.

Thanks!
 

·
Registered
Joined
·
4,493 Posts
Sounds like your alternator is on the way out...13.3v when running is not enough. I have a digital volt meter on the dash...sits solidly between 14 and 14.2 volts with the engine running...no matter what I switch on, it only dips for a second or two them back up to 14.2.
That said, before you buy a new one, make sure you check your battery wires for good contact and that all the ground points are clean and earthing properly...a very common issue on these cars and can cause a multitude of electrical gremlins.
 

·
Registered
Joined
·
86 Posts
Discussion Starter #3
Sounds like your alternator is on the way out...13.3v when running is not enough. I have a digital volt meter on the dash...sits solidly between 14 and 14.2 volts with the engine running...no matter what I switch on, it only dips for a second or two them back up to 14.2.
That said, before you buy a new one, make sure you check your battery wires for good contact and that all the ground points are clean and earthing properly...a very common issue on these cars and can cause a multitude of electrical gremlins.
Thanks for the reply! My alternator never touched 14 V so that might be it. Does the flickering imply that one coil isn't working properly?

The first thing I checked were the earths and connections with voltmeter, seems like they are fine (un)fortunately.

First thing I'm gonna try is to repair the alternator. If irreparable, anybody have experience with lucas alternators? There's no way I'm paying €400 for a bosch alternator.
 

·
Registered
Joined
·
118 Posts
I bought a refurbished Lucas unit from eBay after seeing the costs of a new one. Came to £170 with warranty. It's a bit of the pain to remove and refit on a Brera due to the power steering/Aircon belt, however other than that it's quite a simple job. Alternator works as expected and car stopped idling as oddly ?
 

·
Registered
Joined
·
86 Posts
Discussion Starter #5 (Edited)
Problem solved by replacing the diode plate and voltage regulator. But I need to make a long journey to be sure. I definitely recommend you get electrical faults like this fixed as soon as possible, as it might damage some of the sensitive electronics in the car. My rain sensing wipers started working almost perfectly after fixing the flickering problem.

Thanks George for the recommendation and I ordered a lucas refurb unit, but I wasn't happy with it. Even though it came with a freewheeling pulley, it didn't have the additional damping spring (probably because the pulley with damping spring costs €65 compared to €15 for a non damped one) and everything on it were no name components. No way I am returning my original bosch alternator for this. And I didn't want to pay the stupid €450 for a bosch alternator, so I decided to try fix it. My problem is an intermittent problem, which means finding the problem will be a PITA.

I removed the alternator following this guide: https://www.alfaowner.com/Forum/alf...449-brera-alternator-problem.html#post6281457, 2 changes:
1. You don't need to remove the wheel and wheel well to get to the tensioning pulley, if you have a alternator belt tool which is a long thin bar with a 3/8" socket drive at the end like this. The 3/8" drive fits into the hole in the middle of the tensioning pulley, if you see a picture of the tensioning pulley it's obvious where it is. You need a small extension of maybe 10 mm at the end to clear the engine and you can loosen the belt enough to remove it with one hand. I used a 1/2“ to 3/8“ adapter on the 1/2“ tool which gave me enough clearence to the engine.
2. You don’t need to remove the coolant pipe, removing the throttle body will let you remove the plenum.
Definitely remove the power steering belt as it will put too much strain on the one bolt that's holding the pump.

Having done it, I don’t think you need to remove the alternator to diagnose electrical problems. After gaining access to the alternator, remove the electrical connectors at the back. Remove the back cover which is held on by 2 flat nuts and one philips bolt. Remove the regulator by removing the 2 philips bolts and one philips bolt of the connector from diode pack to regulator. Now slide the regulator downwards to remove it. You now have access to regulator, diode pack, coils and rotor sliprings.

Now for finding the problem, I followed this video:
The alternator is different from the one on the 159 but the concepts are similar.
Before testing, make sure you have a proper connections by scratching the gunk away.

1. Regulator: One surefire way of knowing if the regulator is faulty is if the voltage when the car is running is higher than 15 V. Else you need proper equipment to test it. Just replacing it isn’t a bad idea as over 150k kms, as the brushes would’ve worn 1/2 to 3/4 ths anyway. Costs around €35. Part No: F 00M 145 282

2. Diode pack: See 2nd attached pic. To test the diodes, with the multimeter in diode mode, connect the negative lead to the positive of the alternator. Now connect the positive lead to each diode connection on the inner ring. You should get a reading on the multimeter of around 480 mV. The value isn’t important but if one diode has a value significantly lower than the others, then it’s faulty. If there is no value displayed, i.e. the same reading as when the leads aren’t connected, then that diode has failed open. Now do the test with red lead on the positive pole and black lead on the diodes. You should get no reading, on all diodes. If there is a reading on a diode, that diode has failed open.
Now do the same test for the diodes on the outer ring, instead of the positive pole, now connect to the alternator body i.e. the negative. You should get forward voltage in one diection which should be consistant and no reading in the other direction.

If the diode pack has failed, replacing it is easy. After removing the 3 philips bolts, The coils are connected to the diodes by loops which are just clamped together. Inserting a small flat head screwdriver into the gap and prying them apart is enough to free them. It looks like they aren’t soldered or spotwelded. To fit a new diode pack, sand the coil endings (where they meet the connectors only) to ensure a good connection. Then fit the new diode pack onto the case ensuring the coil endings are inside the connector loops. Using a plier, press together the neck of the loop, so that connector forms a noose shape around the coil ending. Now using pliers, clamp the noose closed very hard so that there is a good tight connection between the coil and the diode pack. There should be no movement what so ever. You can solder it with a soldering iron with atleast 100 W capacity but I think soldering will might damage the diodes. Diode pack costs around €30. Part No: F 00M 144 002

3. Coils: On this alternator, there are 3 coils with 2 endings per coil. To test the coil properly, you need to remove the diodepack. Test with multimeter that there is continiuty on each coil and there are no shorts between the coils. If there is a fault here, then replace alternator as I don’t think you can get coils seperately. Maybe one can buy a cheap alternator and use the coils from that? Hopefully someone with knowledge can confirm.

4. Rotor: To check the rotor, check the continuity between the sliprings, which might be tricky because the opening will be to the bottom. Also check the sliprings for wear, if there is a millimeter of wear, send it to a refurbisher to have it changed. If there is no continuity, it’s faulty. Spares might not be available so same deal as the coils really.

In my case, regulator can’t be tested and the rest didn’t show any faults, so I decided to change the diode pack and regulator and hope for the best. Coils and Rotors are generally very resilient, so 90% of the time the fault will be in the regulator or the diode pack. Also, the freewheel can be broken as well, where it turns without turning the alternator, in which case there will be obvious charging issues. My recommendation is to change the regulator first and check if the problem goes away. It’s cheap enough and quite easy once you gain access to the alternator.

Or you can not be as picky as me and replace with a refurbed alternator :biglaugh:
 

Attachments

1 - 5 of 5 Posts
Top