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Posted by: oldschool Dec 30 2014, 05:28 PM

So I do I test this thing

Posted by: Elliot Cannon Dec 30 2014, 05:55 PM

Test it in another 914. Don't you have more than one?

Posted by: Rand Dec 30 2014, 06:07 PM

Throw it in a lake. If it floats, it passes. Then get a new one, and wonder what else is wrong.

Posted by: oldschool Dec 30 2014, 06:51 PM

..I have a few in my stash....just want to know if I should throw it away...

Posted by: oldschool Dec 30 2014, 06:52 PM

No.... just one now.

Posted by: Spoke Dec 30 2014, 07:56 PM

2 ways to test it.

Put it in the car; start the engine and see if it regulates the battery voltage to about 13.5 to 14V. Must measure at the battery. This assumes the alternator and all wiring are ok.

Test it on the bench. A bit more involved. Put a DC voltage across D+ to D-. Put a load resistor of some value equal to the resistance of the alternator armature; maybe 100 ohms between DF and D-. Vary the dc voltage from 12 to 15V while monitoring DF to D-. Below 13.5V (D+ to D-) the voltage from DF to D- should be near the DC input voltage. Above 14V (D+ to D-), DF should be zero volts. I've never tested one like this but this method should work.

Posted by: oldschool Dec 30 2014, 10:16 PM

Thanks Jerry I guess I'll just put it back and do the test.

Posted by: r_towle Dec 30 2014, 10:26 PM

With a tester, how else....?

Posted by: stugray Dec 31 2014, 02:28 PM

These are basically a relay with an op-amp comparator to control the position.

Above ~14 volts, the relay should open (take the alternator input away from the battery)
Below ~13 volts, the relay should close (putting the alt output back onto the battery).
The deadband (should not change state) is between 13-14.
So if you had a variable voltage power supply, you could check the transition points.

I know the older units in the type-I engines were physical relays and you could hear them buzzing when they were working but hard to hear over the engine noise and are not doing anything unless running.
The newer ones you can buy now (solid state) have no moving parts so make no noise.

Posted by: oldschool Dec 31 2014, 03:18 PM

Posted by: oldschool Dec 31 2014, 03:18 PM

repost