So this is really about my son's 1975 VW Bus, but it applies to 914s because 914-4s use the same Voltage Regulator and Alternator. I'm hoping someone here can help me figure out what is going on.

The problem is that when the weather gets cold, the battery doesn't have enough charge in the morning to start the engine and my son ends up push-starting it (lives on a hill). The only symptom that I've been able to see is that if the car is idling with the headlights on, turning on the blinker will push the electrical load high enough to cause the alternator light to blink in time with the blinker. The glow of the alternator light is fairly dim, but it's easily seen.

Well the '70 teener isn't going anywhere this week since we have 6" of snow on the ground and more coming so I decided to swap batteries and put the teener battery into the bus. They are both Optimas, the only difference is that one is red-top and one is orange-top. The battery from the teener had not been used in a week, but it had plenty of power to start the bus.

Unfortunately, with the teener's battery in place, the bus still had the same issues with the alternator light. So it's pretty clear to me that this is not a battery problem, but how can I tell which component has the problem? The VR is fairly new AFAIK. There's only 3 components to the charging system - how do I know which one has issues?

Check the battery voltage at the terminals while cranking to verify your belief that it's a charging problem. If the battery voltage is good and holding close to 12 volts then maybe all you have is a corroded cable at the battery or the terminals on the starter 12V and gnd cable need cleaning.

clean the grounds, make sure you have good connections to and from the alternator.
check and see if the belt is too lose and slipping.
measure the voltage coming out of the alternator.

maybe it's just time for a new one ...
Andy

This is kinda like my problem.
You have 12.x volts when the car is off and 13.5-14.x when it is running. What do you have?

With the available external regulator, swap it out if you have low voltage when running.

Let's get 'em running.

KT

Just to make sure... "checking the voltage at the terminals" means putting a voltmeter between the positive and negative terminals? No disconnecting of cables is involved?

yes, just + on + and - on -

It doesn't matter wether the cables are connected or not. You test at the cable end with the car running, regarless of what the cable is hooked too. Think cables not battery posts. Battery posts test the battery, cable ends test the electrical system.

Hopefully that's clearer, rather than more confusing. I have a habit of making things more confusing.

To properly test the system, just open the hood and go!
Takes 1 minute.

leave everything as is.

Test part 1: test volts with car OFF. note voltage.
Test part 2: test volts with car ON. note voltage.

report back with notes

KT

Thanks guys! It may be a couple of days before I can test. I'll let you know!

Replace the fuses and clean the "fingers" that hold them in! One of the ones that powers the instruments also has to do with the charging system--making sure the connection is clean and tight will let you charge the battery better, and will keep the alternator light from going on when you turn on the turn signal.

Or at least, is one of the things that can cure that.

--DD