Bad Alternator or Bad Wiring?

[bensdad]

1960 S2 2.25L SWB

The alternator doesn't seem to be charging the battery. I ran a test on the battery and it gives off about 12.4 V while the engine is running or when it is not. Shouldn't it increase once the alternator kicks in?
So...can you bench test an alternator?

I also thought that the wiring might be faulty. Original wiring from what I can tell and it really needs a new wiring harness (prob next job). What gauge wire would you suggest?

Any other ideas?? Thanks so much for any advice you might offer.

[SafeAirOne]

More info needed:

Does it have an alternator conversion? GENERATORS are RPM-sensitive, so you'll see an increase in voltage as the engine revs. Not so much for ALTERNATORS.

Is yours an internally or externally-regulated alternator (most are internally regulated nowadays).

Does it use a sense wire (are there 3 wires coming off the alternator, or just one?

As for the wire gauge to be used, that depends on the amps the wire will be carrying, the length of the wire and the acceptable voltage drop.

[SafeAirOne]

Wire size chart (12v):

[bensdad]

Well, I know for sure that it is an alternator. Don't know if it is internally or externally regulated though. It does appear to have 3 wires attached to it.
thanks guys

[SafeAirOne]

If it's got 3 wires, it's going to be internally regulated, so we can eliminate the original rover voltage regulator then.

Do you have a pic of the alternator?

I'll proceed on the assumption/basis that it is a Delco 10si or 12si 3-wire alternator, though it might not be:




First, you want to make sure all the wire connections on the alternator are good and that there is electrical continuity between the alternator and ground (make sure the alternator case is grounded through the alternator mount).


You will need a multimeter with the voltmeter set on the 20 volts-DC setting.

With the engine running and the red lead on the "BATT" terminal of the alternator and the black lead on a good grounding point, you want to check that more-than-battery voltage is showing on the voltmeter. For instance, if your battery is down to 12.2 volts, the reading on the voltmeter should be 13 volts or more, letting you know that the alternator is trying to recharge the battery. WATCH OUT THAT YOU STAY FAR AWAY FROM THE SPINNING ENGINE COOLING FAN ALONG WITH THE FAN BELT AND ALL THE PULLEYS.

If that didn't produce desirable results, connect the sense terminal (terminal 2 on the Delco alternator) to the BATT terminal on the alternator (...if it isn't connected there already; If it IS, make sure the connection is good). BE CAREFUL NOT TO TOUCH THE WIRE TO THE ALTERNATOR BODY OR ANY GROUND ON THE VEHICLE, or you'll get a big sparky show and have to go in and change your trousers.

Now perform the above voltage test and see if you are getting a good voltage reading.



Alternatively, you could just identify the alternator and take it to a REPUTABLE auto parts store and have them test it. NOTE that the 17 year old kid behind the counter has no idea how to use the alternator testing machine and may kill the alternator himself. They did this to me once.


Additionally, if your multimeter has the ability to test diodes (most do), just take the alternator apart and check the whole thing out yourself. VERY easy to do if you follow along with this, the best video i've seen on the subject:



Good luck, and have fun learning something new!

[o2batsea]

Yeah, bad cell in the battery. At 12.4 it's pretty much dead. So have the alternator tested and have the battery load tested. Between those two checks you will find the problem. Most auto parts shops do those checks for free.