Hi Guys, Starting to work/test my way through a charging problem on my "L". I have already reviewed the older posts . My fuse block and fuses are new. Just so I understand correctly, to test a regulator, if I pull the field wire off the regulator (2 wire system) and put an amp meter lead on it (other lead to ground) With the engine running: 1) I should see voltage. 2) With the headlights on, I should see more voltage 3) At higher RPMs (2,000) I should see decreased voltage. Assuming the above is correct and I have this, With the regulator field wire reconnected, the engine running and lights off: 1) If I pull the red wire off the fuse block (alternator side) on the firewall, and put a lead to it (other to ground) I should see voltage. 2) With the lights on, I should see more voltage. 3) At a higher RPM (2000), I should see decreased voltage Would this be a correct way of isolating the culprit? I have just reinstalled my engine and DREAD the thought of having to change the alternator now. If the alternator is bad, I thought I read where someone used a domestic replacement. Can anyone make a recommendation on year, make and model? Thansk, Steve
Here is how I tested my Voltage Regulator. It is a simple electromagnet with points http://www.ferrarichat.com/forum/206-246/193757-dino-diy-voltage-regulator-testing-ammeter-flicker.html
Steve, If the regulator is ok, and while you're pulling the battery lead off the firewall and if you can get access to the rear cover of the alternator, you could check the 6 rectifier diodes with a multimeter. The resistance between the small bolts which are inside 3 square insulator blocks on the back of the alt should be very small only in one direction, open in the other. Test them both to ground and the alt battery output terminal (with it disconnected, and battery disconnected for safety!) I noticed one diode had been replaced in mine when I tore it down, so they can go bad. Hopefully it's not these and just a bad conection or regulator. Regards Andrew
I think I know which alternator can be used as a replacement if you need it, same part and they are cheap. The L-series had a magnesium pulley which was in the same "dow-7" finish as the cam covers so keep that if you have the original and swap onto the new alternator. Peter had a great thread on rebuilding L-series alternators if you need to. I'm rebuilding mine so I keep the original housings etc.
Andrew, Thank you for your response , I will test the regulator tomorrow. I am somewhat confused. I have replaced the lucas relays today as a matter of course. I have voltage to and from the regulator with key on and I have output power from the alternator with the engine running. Wiring is good from fuse block on firewall to battery, yet I still show a discharge with the engine running and the lights on. Thanks Steve
A glowing alt light is a sign of at least one diode gone bad, gets brighter under more load. Is the voltage at the battery around 14V or so with the engine running and how much does it drop with the lights on? Might also want to check the wiring by measuring the voltage at the alternator output terminal, firewall, regulator and battery. Should be within a fraction of a volt of each other, a bad connection could fry the alt. Do you have the heat shield on the rear of the alternator?
Andrew, Regulator tests OK. Alternator is suspect. do you have a recommendation for a replacement? Thanks, Steve
Steve, See this thread where Peter swapped parts from a new one: http://www.ferrarichat.com/forum/206-246/443842-overhauling-246-alternator.html Peter used the new alt from Superformance and they also have an uprated one if you desire. However, I think the one from a FIAT 124 is identical and much cheaper, the part# A12M124/12/42M cast into the edge of the front cover is the same (also as per the Wallace WSM), search Remy 13072 $92 shipped. Alternator Premium Remy 13075 Reman Fits 71 74 Fiat 124 1 6L L4 | eBay I didn't try this 124 alternator so I can't confirm if the pulley fits, if you go this route please let us know. FYI, the magnesium pulley from mine Matthias confirmed was original and has part# 4177617 cast in the center. I'd be interested to know if yours is the same? Regards, Andrew Image Unavailable, Please Login
Andrew, I did several checks this afternoon including a dedicated line from the alternator lead directly to the battery and it made no difference. I am going to pull the alternator out this weekend. Will let you know about the pulley Thanks for the help Steve
Hello Andrew, Sorry for the late reply. First off, my pulley is Mn with a part number of 4177617, as is yours. I ended up pulling the alternator only to find that in my haste in installing my engine, I had plugged the field wire (exciter wire) into the wrong tab. It never had a chance. Since I was already knee deep into the project, I changed the alternator anyway. I ordered one from my local parts stores and it is the same as a Fiat 124. This unit was made by Letrika part #AAK4518 No mods were necessary. I opted to upgrade to the style with the regulator built in. Life is good again. Again, I appreciate your help. Steve
Steve, No problem and thanks for the pulley info. Good to hear it's charging again. I went ahead and bought a FIAT 124 alternator off ebay for my E-series and held it alongside my L-series unit over the weekend, and the shaft is the same. The only issue might be the 4 nuts retaining the front bearing cover are a little large and interfere with the pulley, they were originally studs hammered over flat and they drilled them out when rebuilding. Regards, Andrew
