two questions

[30-9]

1 - how much voltage should a 6 volt alternator put to battery = when running lights off and then with lights on - My car is reading 6.9

2 - I notice running at night with lights on- my dash lights dim slightly when pressing on brake - this normal?

[JSeery]

Does the car have an alternator or a generator? If alternator the wiring has been modified to some degree. Is it a (+) or (-) ground system? The voltage to the battery is a little on the low side, should be in the >7.0V range. No, the brakes should not dim the dash lights. What wiring does the car have, original or has it been changed/modified? What size is the wiring to the battery, is it sized for a 6V or a 12V? Are the grounds to the tail lights clean/good connections?

[30-9]

thx - 1 wire alt (disconnected regulator) & new battery - no other changes electrically - all org wiring w pos grd 6 volt - wiring size to battery is correct - car ground are clean

[G.M.]

Originally Posted by 30-9

1 - how much voltage should a 6 volt alternator put to battery = when running lights off and then with lights on - My car is reading 6.9

2 - I notice running at night with lights on- my dash lights dim slightly when pressing on brake - this normal?

1 - The battery should read in the 6.3 range before starting the engine. Running at a slow speed above idle, no lights 7.2 to 7.5 max. With lights on as long as the voltage is above 6.7 above idle speeds you are OK. Below 6.3 and you are running off the battery and not charging. This depends on the load from the lights and other power draws. The size of the amp output of the alternator and the RPM's it turns determines the output. A larger pulley cuts down on the output at low RPM's. The Delco type single wire alternators I had didn't charge at low RPM's. I had 24 volt stators installed and they worked perfect with a stock small diameter pulley but I didn't like the look of them.

2 - It's normal for a small drop in voltage when the stop lights are on. This also indicates minimal generator or alternator output.
G.M.

[adileo]

K thx - It makes me wonder if my alternator belt may need tighting - I didn't want to over tighten for fear of ruining water pumps.

[30-9]

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adileo, could that be the case that the belt needs to be tighter?

[G.M.]

I tighten my belts to a TOTAL movement of 1", this won't hurt the water pumps. If you run a real small pulley on the alternator it requires the belt to be to tight. G.M.

[30-9]

Thanks GM for all the good advise - how do u measure the one inch - just judge by eye?

[TJ]

On a flathead I do not run the one wire alternator. I always run an extra wire from the ignition switch to the alternator regulator(exciter) so it charges as soon as the motor fires up.

[G.M.]

Originally Posted by 30-9

Thanks GM for all the good advise - how do u measure the one inch - just judge by eye?

The picture shows how to measure. G.M.