Head light hell

Val

Ok here is what I got and think I understand. I'm no electrician by a long shot but I got a known good headlight relay. Installed and wired. No lights. I checked for 6 volts ( power) coming into relay. I have that. What I don't have is 6 volts at the switch side or lights side of the relay. So I checked ground. I took a jumper wire from ground at battery and clipped to base of relay. No dice. But when I manually operate the relay by tapping the coils on it the lights do come on. So long as I hold the contact down. So I seem to be not getting voltage from the light switch or maybe dimmer switch?  Please advise as I'm about to pull the rest of my hair out!!!

eddiehudson

If you tap the output side of the relay with your ground wire, the relay should click and the lights go on. If the relay clicks but the lights don't go on there is an open in the wiring to the lights or the lights are not grounded. Try grounding the wire at the lights to see if you get a click at the relay. You should have two input terminals and two output terminals. One for high beams and one for lows You don't have to ground the relay base to get it to click.

Val

lights come on when I tap relays. zero volts at relay so working backwards i checked the dimmer by jumper wire on power wire and low beam and high beam. still no dice so i put jumper on power wire at dimmer and the other end of jumper to meter. grounded and shows 003 on meter not 6. So, it seems like head light switch. Or wire issue between headlight switch and dimmer switch.   

Geoff

It's a matter of tracing the voltage from the light switch to the foot switch, to the relay, should be easy enough.  Check the foot switch first, when you turn the light switch on you should have voltage at the terminal from the light switch, and from one of the output terminals, which should switch to the other terminal when depressed.

Val

Geoff, I did that and have just 3 volts at the foot switch. So, I believe my issue lies with the head lamp switch at the dashboard.  However, as you are the prewar car expert may I ask....my fuse box under dash was very loose. Could that be part of my issue? 

eddiehudson

Take the wire from the headlight switch off at the dimmer switch. Then measure the voltage on the wire. Clean up all the connections at the dimmer switch. Also make sure you have a good ground when you're checking for voltage. If you have low voltage on the wire from the headlight switch, work your way backwards. 

50C8DAN

Doesn't take a whole lot of crude and corrosion to drop 6V down to something unuseable.

Val

The connections on the switch look shiny. I have cleaned them before. But I will pull that wire off and see what I have. 

Geoff

If you have three volts only at the foot switch, then the problem lies  in the dash switch or fuse connections. 

Jon B

Val, is this a dual relay?  (One relay unit, but it controls the high and low beam functions of both headlights).  Or is it two separate relay units?

Were you fortunate enough to get the relay wiring diagram?

The relay unit needs to be "told" (by the dimmer switch) whether the high or low beam should be on.  Does one wire run from one of the dimmer switch output terminals to the "high beam" terminal on the relay unit?  And does another wire run from the other dimmer switch output terminal, to the "low beam" terminal on the relay unit?

And is the whole relay unit properly grounded to the car, so there is a complete circuit from dimmer switch to the corresponding terminals on the relay unit?

Now, moving along to the actual headlight circuits, you need a hot wire on the voltage regulator feeding the main power terminal on the relay unit.  Tromping the foot switch directs this power from the hi beam relay to the high beam terminals of both headlights, or from the low beam relay to the low beam terminals of both headlights.

Of course, both headlight sockets will need to have a good ground.  (I have soldered ground wires on my pre-war car's sockets, and screwed them to the car frame.)  This completes the headlight circuits and should result in light!

The ground to the relay unit only completes the dimmer switch circuit.  The headlights themselves will need their own grounds.

You've said that the lights only come on when you manually tap the coils.  The dimmer switch should be activating those coils, not your fingers.  Something is wrong with that dimmer circuit.

By the way, pease don't pull the rest of your hair out.

RichardD

Always use Gardener Bender Ox-Gard Anti-oxidant Compound on all electrical connections. Many restorers of classic cars do {or use another compound}. Bulbs, fuses, crimp connections, screwed connections, etc.........

Val

Jon B yes it is a dual relay. And yes I have the wiring diagram. It is wired correctly. I have tried grounding lights them selves and it makes no difference. I am convinced I have a switch issue. But funny thing is lights worked before I added relay. I'm am gonna pull the foot switch out and remove wire and check voltage to teh foot switch to be sure of voltage. If it still shows 3 volts then It must be headlamp switch. Maybe wire between but I have a new harness installed by Doug WIldrick in 2017. So I kinda doubt its a wire issue.   

Geoff

If it worked before you fitted the relay it has to be something you have not done right.  

Val

Geoff I thought about that too. I double checked my wiring and had my Chapter President also look it over. We both see it as correct. But I am wondering, I had to add some length to the switch side wires. Could be that the splice isn't making a good connection??

Geoff

Anything's possible!

Toddh

Val.  You need to approach this methodically.  Take voltage measurements at each connect point in the circuit, starting at the battery feed.  There’s a bad connection in there some where

Val

Ok so 3 volts at relay, 3 at foot switch. Next I will have to pull radio so that I can get access to head light switch. 

Toddh

If you posted the year of your car, I don’t recall seeing it but on the 41-47’s the headlight switch is held in by 2 machine screws from underneath the dash. Much easier than taking out the radio.  Just disconnect your battery first so your not shorting anything out.  

Val

1939, and the radio is up against the dash board so it will have to come out