1997 850 NA - Aging 100A Alternator

Post by **misha** » 28 Dec 2016, 02:20

Was reading performed on battery terminals or directly on alternator?
I would check it directly on alternator and then on the battery.If readings are different....then voltage drop test is the next step.
Was b+ cable ever replaced?

Post by **xHeart** » 29 Dec 2016, 07:33

misha wrote:Was reading performed on battery terminals or directly on alternator?
I would check it directly on alternator and then on the battery.If readings are different....then voltage drop test is the next step.
Was b+ cable ever replaced?

The reading was on the battery terminals, not on alternator. No, the B+ cable is original.

Is there a Robert-MVS procedure for a "direct reading on alternator"?

firestarterpro · Post by **firestarterpro** » 29 Dec 2016, 07:55

I havent checked my voltage lately, but I have around 380k with an original alternator and a 10 inch subwoofer along with 10 meters of LED light strips connected to my car. I have a 1 farad capacitor before my sub, but I still haven't replaced my alternator regulator yet. However, I do have one on hang in case it goes out.

If it ain't broke, dont fix it just yet, but be prepared!

Post by **misha** » 29 Dec 2016, 08:00

Put multimeter`s negative probe on alternator housing and positive on b+ terminal on alternator.

If b+cable from battery to starter is still original....it`s bad for a long time.
You can add 2awg wire in parallel from starter to battery in 15min.There is no need to remove the old one.

Post by **xHeart** » 29 Dec 2016, 13:41

misha wrote:Put multimeter`s negative probe on alternator housing and positive on b+ terminal on alternator.

...

Above is now in my to-dos.
Meanwhile, after throughly cleaning terminals with wire-brush, and making sure contact locations for the probes are dirt free.

Multimeter at 20 DcV:

- 12.13V - SoC is indeed 50% (engine off)
- 13.9xV: Alternator charging rate at idle-to-1500rpm (running daylight)
- 13.4xV: Alternator charging rate at idle-to-1500rpm with Load (running daylight, radio, trouble lights, windows going up and down, heater fan, wiper, and fog light)
- 0.02 to 0.03V: Voltage drop test negative (-) between idle-to-1500rpm with Load (set up: black probe on negative terminal at the battery for ground, while red probe on alternator housing.

Post by **misha** » 29 Dec 2016, 14:29

Voltage drop on positive side?
Voltage drop on both sides should be performed when cables are warmed up....after about 30 min of driving and before turning engine OFF...with lights,defroster and heating ON.Nothing else.

If you perform testing after cold start,or after engine is been turned off for a while,results will be deceiving because cables are still cold and resistance didn`t built up yet.

Post by **dyn blin** » 29 Dec 2016, 17:14

firestarterpro wrote:I haven't checked my voltage lately, but I have around 380k with an original alternator and a 10 inch subwoofer along with 10 meters of LED light strips connected to my car

Night-time pic, or it's a lie....

Post by **xHeart** » 30 Dec 2016, 10:45

misha wrote:Whatever....it's around 30%.According to the table it's almost discharged.

I wonder how it even cranks with voltage that low.X-heart says that engine turns quickly.In that case i would say that multimeter reading is incorrect....or it was 12.5v instead of 12.05v.

I believe, cold crank amps (CCA) provides the needed juice for a cold start -- right?

Post by **misha** » 30 Dec 2016, 11:04

Cca are presenting the whole battery capacity when it`s fully charged.
It defines striking power of the battery.
Cca defines cold cranking power for specific amount of time at specific temperature....but when battery capacity is low...when battery is low on charge....cca changes according to battery state of charge.

firestarterpro · Post by **firestarterpro** » 04 Jan 2017, 10:34

dyn blin wrote:
firestarterpro wrote:I haven't checked my voltage lately, but I have around 380k with an original alternator and a 10 inch subwoofer along with 10 meters of LED light strips connected to my car
Night-time pic, or it's a lie....

I never told a lie

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