Lights Fade with reduced RPM

[DollyDodge]

All my lights (headlights, tail lights, panel, etc) fad as the rpms reduce. There are really bright as long as the rpms are up, but once the engine goes to idle the light get much dimmer. Is there a way to fix that?

[Allen I.]

Are you at 6 volts with a generator?

[Dave72dt]

You've got a problem that's very common with a generator charging system and not exclusive to Dodge. The industries' answer was the alternator which starts charging at lower rpm. There may or may not be an adjustable brush in the generator that can be moved to help the RPM at which it starts to charge. You may need to kick the idle rpm up a little. Thoroughly check all your grounds and power connections to make sure you are getting full current flow. Clean the contacts in the regulator and make sure the settings are correct.

Last but not least, youi can swap the gen out for an alt or have an alt built into your gen housing.

[greg g]

I concur with the checking the grounds. Especially the headlamps as they are the biggest current draw and any extra resistance adds to the draw. Also if you do not have a ground strap from the body (firewall) to the engine or frame, it always seems a positive thing to do.

I have also run a seperate power line for the brake lights, bypassing the the headlamp circuit. Directly from the bat through a fuse and to the switch. Headlamps stay reasonably bright with the brakes on as they are pullig from the battery, rather than throughthe amp gauge to the lamp circuits.

[ggdad1951]

I concur with the checking the grounds. Especially the headlamps as they are the biggest current draw and any extra resistance adds to the draw. Also if you do not have a ground strap from the body (firewall) to the engine or frame, it always seems a positive thing to do.

nice and punny!

[TodFitch]

Mostly a re-hash of previous posts...

1. Generators don't put out much if anything at idle.

2. So the lights are running off the battery at idle.

3. So any bad connections or high resistance between the generator and the lights will cause the lights to really dim.

Go check all wires, connections and switches both on the power path and the return (ground) path on the lighting circuit for high resistance. The head lights will always dim a little at idle (battery discharge voltage is lower than the charging voltage) but they should not dim much.

[DollyDodge]

Thanks again for all the input. I will check the things that were mentioned. It might be that my memory has slipped, I just don't remember the lights dimming as much when I drove it years ago compared to now.

Answering some of the questions from the string, yes I still have the 6v system (I want to keep it) and I believe the generator is the original one.

I am running the idle rpm at 450. the book said 450 to 500. This weeked I will kick it up a bit.

What resistance level should there be on the headlights. I don't know what values I should look for (I bought a multimeter last weekend and wonder why I didn't do that years ago, it really has helped me with my wiring).

[TodFitch]

When looking for at resistance using any of the inexpensive multi-meters, you should see no measurable resistance in the complete path from the battery to the headlight connector. (And back again through the chassis path.)

Just disconnect your battery, turn on your lights and measure the resistance (ohms) from the battery terminal to the connector on each headlight bulb. Do the same between the ground pin on the light and the ground post on the battery. The value should be as close to zero as your meter can measure.

Alternatively, have the battery connected, turn on the lights. Measure the voltage across the battery terminals. Measure the voltage between the ground and power pins on the headlight bulb while it is on (drawing power). The two voltage measurements should be the same.

If either method shows a problem just start working back from the light until the problem disappears. That will tell you the component that needs attention. Most likely is it a number of individual problems that are all adding up to too much resistance.

[DollyDodge]

Thanks so much for the info on how to measure the resistance. I will have a go at it this weekend

[HanksB3B]

There are 6 volt alternators that can be housed in the original 6 volt generator body. I'd like to see one and know who makes them and for how much, if anyone knows.

Thanks,

Hank

[Merle Coggins]

http://www.gener-nator.com/

Not cheap. Also, it shows the 6v at 50 amps. I believe my generator is a 45 amp unit. Not much gain except maybe at idle.

Merle

[HanksB3B]

Merle,

It is in my opinion a worthy diversion from stock. That, the Disc Brake conversion you did, and one of those $700.00 custom aluminum radiators.

Thanks,

Hank

And now for something OT:

Lake Geneva demolished a Frank Lloyd Wright hotel. Not sure when, but have you ever seen it?

[Merle Coggins]

And now for something OT:

Lake Geneva demolished a Frank Lloyd Wright hotel. Not sure when, but have you ever seen it?

Can't say that I have. I didn't hear about it. Got more info?

[HanksB3B]

but there is a listing in a F.L.W. website. I'll try to find out more my daughter Jennifer lives in Janesville and is often in Lake Geneva.

Hank

[Reg Evans]

Here's a source for a 6 volt modern looking alternator.

http://www.fifthaveinternetgarage.com/parts/index.html

[DollyDodge]

Danged, so many things to think about. I am one of those that likes to keep it was it was, maybe not always the best choice. My old truck and me just poke around in the boonies. I think the only modern add on I will do is seat belts. For now I will hang on to the generator, old brakes, 6 v, etc

[48Dodger]

I understand a generator to be DC and the alternator to be AC. Are the generators less efficent at lower rpms in general or were the older generators not buildt with any performance in mind. I understand the advantages of AC, I'm just curious about how well built the older generators were to begin with.

48D

[TodFitch]

I understand a generator to be DC and the alternator to be AC. Are the generators less efficent at lower rpms in general or were the older generators not buildt with any performance in mind. I understand the advantages of AC, I'm just curious about how well built the older generators were to begin with.

48D

They were built pretty darned well. The basic design lasted in cars for about 40 (roughly 1920 to 1960) years so it could not have been too bad. The weak points on a generator are:

1. Low output at low RPM

2. Difficult to output very high currents for long periods of time. More on that below.

If your electrical needs on the vehicle are not much different than what it originally was designed for the generator should be just fine. If you are adding lots of extra loads (much higher power lights, air conditioning, high power sound system, etc.) then you probably want an alternator. If you are running stock or nearly stock electrical loads no problem.

Back to point 2 above. Basically an alternator and generator work on the same principle: A coil of wire in a changing magnetic field. The difference is that a generator has a magnetic field in a fixed location on the generator case and the coils where the power is picked up are rotating on the armature. So the power needs to be transmitted through the brushes and commutator to get it out to where it is useful. There is a limit to how much current you can do that with without burning up the bushes and causing arcing damage on the commutator.

An alternator fixes the output (high current) coils in the housing and rotates the magnetic field. So you have a slip ring type setup (no arcing as the bushes dross from one commutator pad to the next) and the field coils always run at a relatively low current. So you don't have to fight brush wear, bush arching, etc. as you scale up the alternator to provide more power. Also, they don't bother having the alternator "self energize" the same way so the alternator does not need large soft iron cores on the case so it is more easily ventilated it to keep it cool.

[Dave72dt]

An excellant reply by TodFitch.

Something else that can be done to help out idle gen output is to put a smaller pulley on it. That will increase the speed the gen is running without increasing the engine rpm.

[48Dodger]

So you could say an Alternator IS the high performance version of a Generator...at least when we're talking cars.

I remember reading about Edison (DC) and Tesla (AC) fighting over the best use of power. DC was like a kid (electron) running from one side of the room to the other, where AC (electrons) was a bunch of kids standing next to each other across the room pushing on each others shoulders....simple, I know. In the spirit communicating on the forum, instead of using google, does or has a 12volt DC system ever existed?

48D

[Frank Elder]

An excellant reply by TodFitch.

Something else that can be done to help out idle gen output is to put a smaller pulley on it. That will increase the speed the gen is running without increasing the engine rpm.

Dave, a smaller pulley won't burn up the genny? Not by any means a expert , but I would think the genny was engineered with a specific pulley size in mind...what about stress on the VR?

[Dave72dt]

Yes, 12v DC systems were used into the mid sixties when the alternator became commonplace.

[Allen I.]

I bought one of those alternators from 5th Ave a couple years ago after my generator bit it (horrible sounds, metal shavings, it was ugly). Just prior to, I had dimming problems as well.

But I do not write this to say your generator is going to have a catastrophic failure but to say that I am very happy with the alternator. You can find them cheaper but the customer service when I have called has been excellent.

[Merle Coggins]

, does or has a 12volt DC system ever existed?

48D

Umm... 12 volt DC systems are used in most vehicles on the road today.

Yes, alternators produce an alternating current (AC) but it is rectified into a DC (direct current) before it leaves the alternator. Rectification is done through a series of diodes. And generators also produce an alternating current within the armature and it is coveted to DC current through the commutator and brushes.

Merle

[48Dodger]

Umm... 12 volt DC systems are used in most vehicles on the road today.

Yes, alternators produce an alternating current (AC) but it is rectified into a DC (direct current) before it leaves the alternator. Rectification is done through a series of diodes. And generators also produce an alternating current within the armature and it is coveted to DC current through the commutator and brushes.

Merle

I understand 12 volt batteries are DC and Alternators (AC) are converted with diodes because of this, I was wondering if there was ever a SYSTEM, ie 12 volt batt and Generator to match that existed.

48D