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Old 08-07-2020, 09:00 AM   #1
40ford
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Default Dim Headlights on 40:

I have posted on this problem before but I am back at trying to figure this problem out!With both headlights out and car not running I am getting about 5.50 at the pig tail.If I install one headlight and it burning I check the other pig tail and it is about 4.5.Is this normal?I have installed new headlight switch,dimmer switch,good battery,new regulator,generator has been checked,battery cables new and big.When driving car at night headlights are weak and when I put on brakes the dash lights go dim and headlights get even weaker.Any suggestions on this problem?I refrain from driving at night because lights are crappy!
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Old 08-07-2020, 09:23 AM   #2
marko39
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Default Re: Dim Headlights on 40:

You should have battery voltage at lights. You must work backwards from lights to see where your voltage loss is. Do you have wiring diagram? Is this a new wiring harness?
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Old 08-07-2020, 09:25 AM   #3
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Default Re: Dim Headlights on 40:

You don't mention grounds. Make sure you have good (clean shiny) grounds everywhere including between your fenders and the body and the body and the battery. What you describe happens often with fresh restorations where everything is painted everywhere.
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Old 08-07-2020, 10:36 AM   #4
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Default Re: Dim Headlights on 40:

Mr Deuce Roadster is Correct. I put a better ground on my 40 headlight and watched them get brighter when the ground improved
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Old 08-07-2020, 11:14 AM   #5
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Default Re: Dim Headlights on 40:

Theoretical guess here:

Original post said: "when I put on brakes the dash lights go dim and headlights get even weaker". That makes me think that when brake lights go on the entire ground bus (the body of the car) is being charged, reducing its ability to take-on ground voltage from the other lights. So why is the ground bus not immediately discharging to the battery as it should?

I would suggest cleaning/tightening the battery-to-body cable connections.

Last edited by JayChicago; 08-07-2020 at 11:49 AM.
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Old 08-07-2020, 11:57 AM   #6
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Default Re: Dim Headlights on 40:

Quote:
Originally Posted by JayChicago View Post
Theoretical guess here:

Original post said: "when I put on brakes the dash lights go dim and headlights get even weaker". That makes me think that when brake lights go on the entire ground bus (the body of the car) is being charged, reducing its ability to take-on ground voltage. So why is the ground bus not immediately discharging to the battery as it should?

I would suggest cleaning/tightening the battery-to-body cable connections.
I agree looks like body has either no ground cable or a weak ground cable.
Grounding is a lot like lightning it will seek a path of ground usually where
you do not want it. I have seen smoked - melted, from speedometer cables
to E brake cables to choke / throttle cables cause the system is 'gasping' for
ground. Just look at these new cars ground wires all over cause most of the
vehicle is plastic. Wood and fiberglass boats = a mile of grounds. My best
friend is many jumper wires, a test light and volt meter. I grew up with
6volts and my father got into road rage with blinding mirrors pulling over
then following said car blasting him with his high beams LOL causing a mad
mommy good ole days
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Old 08-07-2020, 01:44 PM   #7
40ford
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Default Re: Dim Headlights on 40:

I can't figure it out.I have about 6.20 volts going to the headlight switch.Don't look like there is about 5 volts going out?I got about 5 volts at the dimmer switch.For some reason the voltage at headlight pig tails went from about 5.50 to 5 volts.I have unplugged all my other lights one at a time with no change in voltage at headlights?I thought some other light was draining voltage real bad.I am not an electrician expert so I am still lost.At battery I have new woven ground to firewall and then another from there to nut on head?Is this the way a 40 should be set up?
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Old 08-07-2020, 01:57 PM   #8
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Default Re: Dim Headlights on 40:

Quote:
Originally Posted by 40ford View Post
I can't figure it out.I have about 6.20 volts going to the headlight switch.Don't look like there is about 5 volts going out?I got about 5 volts at the dimmer switch.For some reason the voltage at headlight pig tails went from about 5.50 to 5 volts.I have unplugged all my other lights one at a time with no change in voltage at headlights?I thought some other light was draining voltage real bad.I am not an electrician expert so I am still lost.At battery I have new woven ground to firewall and then another from there to nut on head?Is this the way a 40 should be set up?
Be 100% certain that where you have those grounds, the area beneath is free of paint. I "hide" an external tooth lock washer between my cable ends the adjacent surface(s).
The dimmer switch is often a culprit in this circuit. You might try bypassing it for the moment and see how the results may change.
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Old 08-07-2020, 02:27 PM   #9
Kurt in NJ
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Default Re: Dim Headlights on 40:

So you are loosing voltage in the headlight switch, is it reproduction, or original ford--- the cheating cure is to put heavy power wire to relay as feed, and use weak headlight switch to work relay
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Old 08-07-2020, 03:56 PM   #10
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Default Re: Dim Headlights on 40:

I agree, seems like a bad headlight switch if there is 1+ volt drop through the switch. But I don't think that explains the other symptoms, which seems like a whole-car ground problem.

OP said " At battery I have new woven ground to firewall and then another from there to nut on head" I would try re-doing that connection at the firewall, trying to get the best metal-to-metal contact there.
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Old 08-07-2020, 04:07 PM   #11
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Default Re: Dim Headlights on 40:

Check your voltage from the negative (-) on the bulb (center) socket to the positive (+) directly on the battery. I am assuming you still have a positive ground. You might need a length of wire to make those connections. If you get a full 6 volts, you have a bad ground.

Also, what gauge wire are you running to the headlights?
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Old 08-07-2020, 04:10 PM   #12
40ford
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Default Re: Dim Headlights on 40:

Headlight switch came from Carpenters.I still looks like to me it is the switch also.I guess I could just by pass the switch with jumper wire and see what I have.It still bothers me about the battery gauge not reading in the green going down the road about 60mph.May be the gauge though but it is NOS.
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Old 08-07-2020, 04:38 PM   #13
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Default Re: Dim Headlights on 40:

A fire wall ground is good but your lights are connected to the fenders so a ground wire from the battery (or close ) to the bulb holder is better , Yes not original .set up a tempey ground and touch it on the reflector at night and see how bright ,if it improves it . Modern cars have a separate ground ,Ted
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Old 08-07-2020, 05:17 PM   #14
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Default Re: Dim Headlights on 40:

Are we sure the car has 6 volt headlight units? Not 12?
Take one out, leave it plugged on to the wires and run a jumper wire from the ground terminal on the back of the sealed beam unit to a good ground on the car to see if the makes the light brighten.
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Old 08-07-2020, 06:53 PM   #15
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Default Re: Dim Headlights on 40:

I'm mostly repeating what has already been posted, but I would make up some good jumper wires and start doing some checking. See what you get with each.

Jumper across the light switch from the hot wire to the wire going to the dimmer switch.

If that isn't the issue, try a jumper around the dimmer switch.

Next, try a jumper from the headlight ground stright back to the battery.

Etc, until you find the problem(s).

Grounds can always be a major issue, but the lighting switch reading seems suspect.
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Old 08-07-2020, 06:57 PM   #16
40ford
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Default Re: Dim Headlights on 40:

Quote:
Originally Posted by Aarongriffey View Post
Are we sure the car has 6 volt headlight units? Not 12?
Take one out, leave it plugged on to the wires and run a jumper wire from the ground terminal on the back of the sealed beam unit to a good ground on the car to see if the makes the light brighten.
Both of the headlight sealed beam bulbs are 6 volts.I have tryed another ground wire to bulb and got no change in brightness.
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Old 08-07-2020, 07:26 PM   #17
joe 1950
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Default Re: Dim Headlights on 40:

Every thing mentioned is very good info but what is the generator putting out for voltage at 1500 rpm you should be @ 7.5 volts with every thing turned off check your generator output also on my 50 cpe i have the pos cable to the cyl head as per factory and i also installed a large braided strap from bell housing to body good luck keep us informed
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Old 08-07-2020, 08:12 PM   #18
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Default Re: Dim Headlights on 40:

Hope I am not repeating ,Cold solder out let wire on the light switch maybe ,Can he do what you and others said on post 12 ,run a hot wire to back of the bulb , look for change ,
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Old 08-08-2020, 06:24 AM   #19
40ford
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Default Re: Dim Headlights on 40:

I think I will just get another cable and run it from maybe a hog head bolt to the frame under car.I don't think this would hurt and it may help?Would it matter if it was just a cable or should it be a woven ground strap?
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Old 08-08-2020, 07:44 AM   #20
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Default Re: Dim Headlights on 40:

"not reading in the green going down the road about 60mph."


What's the fix for this ?? I also have this problem. Gen and regulator have been gone through.
Paul in CT
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