VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt Headlight/Charging Issue

When I turn the headlights on, even at highway speed, the ammeter drops to almost max discharge. The car is a stock 38 Master coupe.

The wiring harness is new from YNZ and has been tripple checked to make sure all connections are correct.

With the headlight bulbs out & car at fast idle the output at the GEN tab on the regulator shows 7.6 volts and battery voltage at the BAT tab shows 7.4. With the headlight switch on, using my multi-meter I checked the voltage in the bulb socket at the low beam connector. It showed 6.3 volts. Both headlights checked the same. I then checked the voltage at the junction block where the main harness connects to the headlight pigtail and got the same 6.3 reading. To rule out a bad ground I used several gounding points on and behind the headlight buckets, each produced the same reading.

My thinking is the voltage drop to the headlights is not normal and may be related to the high amperage draw at the ammeter. I think the problem may be a dirty switch. I assume the switch can be taken apart and cleaned??? If so how does the knob & shaft come out? I've not been able to figure that one out.

Am I headed in the correct direction or headed down the wrong path? All ideas are welcome.

You may want to check out the dimmer switch or the connection from the Bat post on the regulator to the ampmeter and then to the headlight switch. Does your car use a headlight relay? if so it should also be checked for leakage.
Tiny do you have a shop manual with a schematic or wireing diagram of your car?

The drop to 6V would be normal with the lights on.The amp drop at the meter indiactes the generator is not putting out the required amps,(takes about 15 amps to light the lights) or there is one huge draw some place...should pop the fuse or something get hot...or the regulator is not calling for more amps.
If you full field the generator (ground the field terminal) the generator should charge way over on the ammeter (do only briefly)..lights on or off.

Here is the wiring diagram: http://i47.photobucket.com/albums/f167/Tinys1938/38wiring.jpg
It's out of the manual but there are two inaccuracies. As viewed to read it the ammeter is turned 90 deg. counter clockwise from how it actually is in the car. In the car the fuse is horizontal at the bottom of the ammeter. Also the two connections shown on the battery side of the ammeter are actually one connection. The heavy wire from the foot starter/battery and the lighter wire from the light switch both connect to the same post at the fuse. It's the only post on that side of the ammeter.

I hadn't thought about the dimmer switch. It works but was gummed up when I got the car. I put a shot of WD40 into it & got it working. How would I check it to see if it's the problem?

There is no relay.

One major problem I have is I don't have a diagnostic ammeter. My multi-meter only goes to 10 amps. I thought about tweaking the current regulator coil in the voltage regulator but I don't have a way to measure how much it's putting out. I guess it's time to buy an ammeter. To the store I go......

Correct me if I'm wrong. At a fast idle, if I turn on the headlights and connect the ammeter (is series) to the BAT terminal of the voltage regulator, the ammeter should show about 15 amps. If not I need to adjust the current reg up a bit until it does?

When you reinstalled your generator after taking it back to the shop to have it checked out, did you re-polarize it first?

:confused: :confused:

You can eleminate the dimmer switch by disconnecting the feed wire and one of the wires leading to the head lamps (high or low beam)...then connect the two disconnected wires together,(power and headlight) and rev up the engine with the lights on.

Cleaning the dimmer switch with WD-40 usually does it for me, sometime I have soaked it for a while then used simply green and sprayed it ( under the car) then washed it off with a water hose and when dry it was as good as new.

CRC Electric Parts Cleaner works great too.

Tiny,
The regulator on your '38 has just the cutout and voltage regulator in the reg unit,as the generator should be the fixed third brush type.
The fixed third brush limits the current output of the generator to a maximum of around 25 amperes,and the voltage regulator stops any over charging,by limiting the output voltage to a maximum of 8.2 to 8.4 volts.
If you have a workshop manual,it should show you the necessary test connections,and give you some ideas.It's possible that the regulator will need to be overhauled,and have all the air gaps re-set,and then re-calibrated with your generator to ensure it's working properly.

:)

I did repolarize the generator. It charges fine until I turn the headlights on. If I turn the park lights on it drops to discharge and slowly comes up to the neutral position & or shows a slight charge. When I pull the switch all the way out it drops to almost full discharge & stays there.

I thought about Chevgene's method of bypassing the dimmer switch this afternoon. I haven't tried it yet but it's on tomorrows list of things to do. :) I'm really hoping that's the problem because that's a relatively easy fix.

My coupe doesn't have the third brush generator setup on it anymore. It was changed before I got it to the later model setup with the three coil regulator & two brush generator.

I haven't been able to find an affordable digital ammeter so I'm going to borrow an analog accessory ammeter from my brother to check the current output. That's on tomorrows list too. Thanks for all the ideas guys!!!!

Yes JYD, CRC Electric Parts Cleaner is a good product. I haven't had any of it since I left my regular paying job back in 1997!

I apologize for being tardy in an update but I spent the weekend in ICU and have been a little slow in getting back up to speed.

It looks like the main culprit may have been the voltage regulator. The current regulator points were less than pristine. I cleaned them up some and it's doing better now. When I turn the headlights on now the pointer stays in the center of the ammeter. Thanks for all the ideas guys.