All lights working but my headlights

[agouge888]

My headlights were working when I got my ‘74 620 a few months ago. For some reason... ....front, rear and side are still working, but I have no power to my headlights on bright or dim.  I tested the terminals and getting no voltage at the pigtails. Is there a “next step” to check so I’m not chasing my tail?

Thanks,

 

Andy

[datzenmike]

OK find the fuse box by your left knee. Look on the upper side for a red wire. The fuse with the red wire going to it is for the headlamps.

 

Wiggle it... see if the lights come on. do the lights come on???

 

YES... problem solved go to the bottom

NO... place a quarter* across the terminal. (*always carry a quarter and some spare fuses) Lights come on???

 

YES... replace the blown fuse

NO... confirm the red wire has power with meter. Got power on red???

 

YES?.... pull headlamp switch all the way out 15-20 times to polish the contacts inside. Lights work?

 

YES... problem solved

NO... You have power to the switch but not getting through, switch seems to be the problem. Try unplugging the headlamp switch and plugging it in to make better contact.

 

 

The fuse box clips are a copper alloy and will tarnish like an old penny. This will remove 90% of any future electrical problems. The best easy solution (pun intended) for cleaning copper is from Martha Stewart. Unplug the fuse box and remove the two screws holding it to the bottom of the dash. Remove the cover, (if it has one) and take out all the fuses, keeping track f them. Here I would suggest you simply replace them with new ones. Make a solution of lemon juice and salt, enough to fill a small container that the fuse box can be submerged in. Wash the fuse box in dish soap and water and a scrubby brush. I save all my old tooth brushes for these and other jobs. Rinse, and place in the lemon salt solution over night. You can swirl it around a few times if you wish. In the morning rinse and dry. Put in the new fuses and install.

 

Like a new copper penny...

[agouge888]

Thanks so much for the check list...that’s perfect. I checked and I have power at the fuse box on the light circuit. I pulled the headlight switch in and out many times to clean the terminal. With the switch pulled out/on, I ran my test light. While connected to the pigtail, I checked the 4 soldered terminals on top of headlight switch block where the 4 wires connect on top and checked them with a test light. While the switch is out halfway (park lights) I had 3 terminals light up, and with the switch pulled out (headlights) I had all 4 terminals light up which I’m guessing is correct and working.   With headlight switch pulled....I ran a jumper wire from the positive side of the battery to the back of the actual headlight terminal and all 4 headlights lite up. What am missing in between? 

 

Thanks for for helping me figure this thing out,

 

Andy

agouge888

[datzenmike]

The only other thing between the light switch and the bulbs is the headlight relay. I think you'll find it near the right side headlamps on the engine side of the  rad support maybe on the right side of the rad. It'll be a small metal box with rounded corners and have 4 wires going to it.

Red

Red.Yellow

Red/White and

Red/Black.

 

Wire may be off? The Red is the input power from the fuse box. Red/White powers ALL HI beams and Red/Black powers ALL LO beams. The Red/Yellow is the switch to ground on the turn signal stalk that select HI or Lo.

[agouge888]

Thanks for the reply. I unwrapped part of the factory wire bundle just after it comes thru the passenger side firewall. I have a tool to penetrate the wire so I can hook to it without hurting it. so From the battery....I put power to the large red wire and the lights came on.....the brights and everything work as they shouldlike normal. I checked for ground on the large black wire in the same bundled area. I have ground on the black wire. I also found out that I am getting ground on the same large red wire that had power on. What’s the deal?  We tried to trace the wires with a meter that “chases shorts”and it seemed to get some odd readings just as the bundle separates and heads to the alternator.  Is there any way the alternator could be causing my problem? Probably sounds crazy. My charging light on the dash lights up quite a bit and the battery when running charges at 11.89.  Didn’t know if the alternator can short somehow and in turn...cause the ground issue and headlights not to work. Let me know your thoughts.

 

thanks,

 

Andy

[datzenmike]

 Lets back up. Check the headlamps for power. Do the headlamps have power when the headlamp switch is on?

[agouge888]

When the switch is all the way pulled out... there is no power at the headlights or headlight pigtails.

 

thanks,

 

Andy

[datzenmike]

Yeah too many balls in the air.

 

Sorry, all head lamps ON THE 620 are grounded and power to the  Hi or LOW is switched by the headlight relay. So the red power wire from the headlamp switch goes to the relay which sends it to either HI or LOW beams.

 

Find the headlamp relay which is close to the passenger side HI beam lamp, probably between it and the rad on the inside of the rad support. Power seems to not be getting past here. Maybe relay unplugged or something.

 

Sorry for confusion, 720s are switched ground and so is my 710.

[agouge888]

Mike thanks for all the help. I spent 14 hrs looking for my problem and threw in the towel. The Auto Electric place locally tracked it down to some sort of burnt wire on the pigtail behind the glovebox. They ran a dedicated wire and fixed it. Also got my alt charging ( bad regulator) and loose terminal on my alternator.  Thanks for all of the input and help. Sorry for my confusing ramble trying to describe my wiring. Hey..my wipers even sped up now:)

 

Andy