Headlight relay verification

[JSabah]

4 hours ago, Sniper said:

I don't believe I said anything about the " "Battery" terminal of the voltage regulator ".    I believe I said the output stud of the alternator is where I would source the 12V for the headlights if converting to relays.  Make sure you use a fusible link or a fuse where ever you source your voltage. 

looking back, I see you are correct.... but I don’t have an alternator. I have a generator. Does that change things? If not would you connect to the Field or Armature (sorry the electrics are such a mystery to me)? And just out of curiosity (seriously trying to learn here) wouldn’t you want the power to the lights conditioned thru the voltage regulator ?

[greg g]

Pulling power from the generator means you only have lights when the engine is running.  90% of the time that's probably ok, but if you are driving around at night and loose the fan belt you got nothing.  Power for the relays should come from the battery, easiest place is the battery side terminal for the starter solenoid if not from the battery itself.

[JSabah]

On 12/3/2019 at 6:18 PM, Sniper said:

I don't believe I said anything about the " "Battery" terminal of the voltage regulator ".    I believe I said the output stud of the alternator is where I would source the 12V for the headlights if converting to relays.  Make sure you use a fusible link or a fuse where ever you source your voltage. 

sorry for my denseness but to me the Battery terminal on the voltage regulator  IS on the opposite side of the ammeter (see pink on attached picture). I was just trying to avoid running the wire all the way into the cab and having to get under the dash again. Isn’t the output of the generator (yes, I’m still on a generator) going to the voltage regulator ? And wouldn’t you want the power source to be conditioned thru the regulator?  
 

also, I’m using a 12ga wire as the power source with a 15 amp fuse... and I’ve converted to 12v. 
 

 

[Sniper]

the regulator doesn't "condition" the power per se.  It controls the generator by looking at the output of the generator and telling it to increase or decrease the generator's output.  Any load you put on the regulator's input will tend to make it see a lower output from the generator than is true.    But if you are hooking up to the regulator's battery terminal (this is an output from the regulator) then you should be good.  You pic was too small for me to read it and blowing it up make it too fuzzy, old eyes.  So I dug into my 36-42 manual and read the drawings there.  I assume it's the same set up, I know assume...

[desoto1939]

ON my 39 Desoto I have the foot starter pedal and the starter selinoid is bolted on top of the starter motor at the selinoid. which also has the battery cable connection.

 

The 6 volt headlight relay is mounted to the firewall near my voltage regulator.  I ran a 10 gage wire fromt he battery connect on the selinoid to the headlight relay to the battery side and then wired the appropriate low and high beams from the dimmer switch that is located on the floor of the car.

 

So my headlight switch runs power to the dimmer switch and then it was originally setup to run wires to the junction block in the engine bay and then the appropriate wires ran to each headlight bulb.

 

When using the relay you lessen the amount of voltage running and you are no longer pulling all the volts/amp throught the headlight switch but by powering the relay fromt he battery use thave shorten the amount of wire and run that needs to supply electrical curren to the headlight and then they will be brighter.  This was done when the 39 and back cars switch over to sealed beams instead of the old style bulbs.

 

Rich Hartung

[Sniper]

I just converted to LED headlights, after going 12V.  Much less current draw with the LED headlights.  I could put in relays, but I've also got a new headlight switch and new wiring.

[JSabah]

Since I don’t know the condition of my switches (other than presumably working) and since I went to 12v (halving the amps), I decided to use 2 relays and hide them where the connection block is. I used the existing (new harness) wires from the hi/lo foot switch as the trigger wires (power to the relay coil) and run a new ground from the relays to the frame. As for the high power side, Understanding that if fan belt breaks or I have other trouble there will be no headlights, I am picking up the power from the generator side of the ammeter at the BATT terminal of the voltage regulator  using 12ga wire and a 20 amp fuse (I can always move the source to the battery, but 1) if there is any issue, I’ll be calling AAA or Hagerty and 2) the likelihood of night driving is minimal ).  Thanks for all the help and teaching moments 

[Sniper]

Nice work, clean install.

[JBNeal]

additional information - Headlight Relay Instructions

[Pete]

Hi all,

 

Attached are the installation instructions for the Auto-Lite HRB-4201 headlight relay. If you are looking for authenticity these are period correct as they came on Studebakers and Hudsons from 1939 - 41.

 

I have one of these on both my '38 Dodge Brothers pickup and my '39 Plymouth touring sedan. They work well. They come with a 14 amp fuse. I needed up replace that with a 20 amp to handle the increased draw of halogen headlights.

 

The hookup is easy. You only need one relay, and it installs in series on the wire from the headlight switch to the foot dimmer switch. This way both the high and low beams go through the relay. I put my relays on the firewall low on the driver's side.

 

I see these on eBay often. Mine has never given me any trouble.

 

Pete

Auto-Lite Headlight Relay Installation Instructions.pdf

[DJK]

I installed a period correct relay(Blue Streak) with a minor change. The relay is between the light switch and dimmer as opposed to between the dimmer and hi beam only lights. This way it works for low and hi beam. During the process I found the nut securing the bat feed to the light switch was LOOSE!!!! Did not have to cut or modify any existing wires or terminals, just added a ground and feed wire for the system.

[Pete]

Hi all,

 

I found another Auto-Lite instruction sheet for installing a headlight relay. These instructions appear to be for Studebakers, so some of the part numbers may not apply to Mopars.

 

Pete