How to identify alternator and regulator ?
 

On my 74 i believe there are 2 possible alternators from standard: motorola or marchal, which one with a different type of reg.
I have a marchal regulator (which i suspect to be faulty). If replacement us needed, it will have to be of the same type ?
Searching in PP it looks like the modern equivalent is the one from valeo, not from bosch. Anyone can confirm ?

I have the Marchal alternator. The regulator, on the driver side engine compartment wall, next to the CDI box proved defective. I replaced it with a German made Uggi and it is working fine now. The replacement eliminated intermittent charging and a bouncing tach.

I have a marchal reg, does it mean i have a marchal alt ?
And i have a bouncing tacho for a long time... Did yours bounce all the time or mostly on upshifts / downshifts ?

Could the brand be Huco ?

Sorry Prebordao, you are absolutely correct. The new one is a HuCO with a couple of those weird little German dots over the u. My tach does not bounce anymore. It is steady thanks to the voltage regulator change. When it gets over 4k, on the way up, it will sometimes jump up to over 5k but I think that might be a problem with the tach, as described on some other recent threads re tach behavior, and may be related to nearly 40 year old electronics within the tachometer itself. Previous to the voltage regulator swap the tach bounced at all rpm, never holding steady. Remember your tach runs off the electrical signal from the distributor and is influenced by the entire electrical system to some degree. If you change the Marchal voltage regulator and it helps but does not give a complete cure to the tach, look to other electrical connections as well as the ignition wires. At least your charging system should work better with a new voltage regulator. Best of luck!

Thanks! I already found and ordered one from ebay. Let's see.

Bouncing tach can also be a worn set of points....

No points here.

Well than that's probably not it :-)

Ok, my problem could be with the alternator or the regulator. Is there any test / check that i could do to find out ?

Symptoms are: red charging light always on, at rest voltage at battery is 12.5, when idling drops to 11.5-12

You should be getting ~13.5VDC when engine running. More (e.g., 14+VDC) likely indicated bad VR; if less, then either 1) loose belt, 2) faulty VR, or 3) faulty alternator. 11.5-12.0 VDC at idle is way too low.


Good luck

Assuming the battery is sound, try these (in order of preference):

Make sure all the grounds (earths) are clean and make good contact.
Make sure the connections at the battery are clean and have good contact.
Remove voltage regulator (it should be external on your '74), remove cover from regulator, clean regulator points (points file works well, or fine sand-paper). These older type regulators can also be cleaned with electronic cleaner and adjusted (search - Google - for a procedure).

If the above doesn't help, replace regulator.

Finally, replace or rebuild alternator.

Jerry M
'78 SC