OK, I took the advice of you guys and got the courage to install relays on my headlights. Before I started, I checked the wiring coming from the high beam switch on the floor going to the headlights to find out which wire is high beam and low beam. When I put the lights on the low beams it seems OK and the lights work fine. I checked the wires one low beam and they appear OK. I put a light to the high beam wire (while the low beams are on) and notice the test light has a faint weak light to it? There shouldn't be any light at all I would think? When I push the highbeam switch on the floor, the high beams come on for a about a minute and then the lights shut off, blowing the fuse to the headlight switch. Any suggestions on what's going on? I need to fix this before I can install the relays. Could this be a defective high beam switch? The wiring looks OK. Or could this be the light switch itself?

 

If you have an ohm meter, can you check wiring at the headlight, undo /remove the wires from the headlight, then with one side of meter to ground / chassis (no voltage to circuit) measure the resistance of both wires. Low resistance reading or zero ohms would indicate short to ground. Could be damaged power wire ?

Next with headlight still removed, check dc voltage on each wire , one side of meter to ground measure ..low beam then high beam voltage. Should both be system voltage 6 V?

Tom

 

Sounds like the dimmer switch to me. As a test put a jumper wire from incoming powerwire to outgoing highbeam wire. This will bypass the dimmer switch and tell you if it is the dimmer switch or something else. Let us know what you find.

 

I appreciate the advice. I went through the wiring again, checking the headlight switch. Looks OK. I took the high beam switch out. When I pull the headlight switch on I get juice to the power (center) and juice to the low beam (left terminal) If I place the continuity light on the high beam side post I get a dim light. So then I went to the headlight. I found whoever worked on this truck before me didn't have a clue. I have my work cut out for me on this one. The headlight screws holding the bulbs in are stripped and the wrong one. (big deal right) The connections on the blub itself are plain clips and are very loose and possible touch each other? I also made a comparison and it looks like one side is different from the other. What I mean is the ground wire is in a different position (middle) on one headlight and to the left on the driver's side headlight??????? I'm going to get the actual 3prong plugs tomorrow at the auto parts store and do this right. I do need help on which wire goes where? Looking at the 3 prong headlight, where does the low beam wire go, is ground in the middle and high beam to left etc. Maybe someone could give me advice. I'm sure this could be a problem if the wires aren't correct? Now you guys can understand why I hate electrical wiring. I'll let you guys know what I find.

 

You've got it easy in comparison to the plate of spagetti I have under my dash thanks to clueless other's work. It's been some time since I've wired sealed beams, but IIRC the center terminal is the common ground, but I would have to test one by putting power to it to see which is the high and low beam side. A continuity tested is a handy tool, but doesn't always give the complete story. Go to your local DIY store and pic up a volt-ohm meter. Doesn't need to be fancy one, a 10-15.00 one will do anything you want. install the battery in it, and connect the probes to the red and black terminals. Turn the rotory dial to the highest resistance setting (probably designated by a horseshoe on feet symbol for ohm) and if there is a function switch set it for resistance or ohm as well. Now touch the two probe tips together and the needle should jump across the meter face. You are ready to check out your switches. Remove the wires from the high beam switch. Touch one terminal on the switch with one probe and the other one with the other probe. The meter should read zero if the switch is on low beams and high when the switch is switched to high beam. When the switch is off (low beam) touching and removing one of the probes should not change the zero reading as long as your fingers are also not touching the terminals or the probe tips. (your body is a weak conductor, try touching the probe tips with two fingers to read your body's resistance.) If you are getting a significant reading with the probe touching with the switch off, the switch is defective. You can test the headlight switch the same way.
My guess is tho the reason you are having problems is that the two headlights wired differently/improperly is giving you a feedback of power thru one headlites low beam to the other's high beam circuit and to ground when you turn the high beams on.

 

Lower

This may not help you this time, but it likely will eventually. Always make sure the ground is perfect whenever you see confusing things. Electricity can backfeed, and do things that defy logic when the ground isn't good. The guys have probably offered the solution already, but make sure the headlight grounds are good before you go too much farther. And do your test light checks with both headlights removed.

 

I've been trying to find a diagram for the old sealed beam headlight plugs, but no luck so far. I'm really not sure which is the ground terminal. Sealed beams havent been used on new cars for the last 30 or so years.

 

Being an old school 12 volt electrician here, when I run into problems like this I run temporary jumper wires and grounds. That tells you immediately what you want to know and where to look. More than likely your effie may need a new wire job and it's not that difficult. Replace your temps with permanent wiring as you find the problem. Just don't do like I did and do it all at once:



Actually, thru the magic of 'labeling wires' it was a piece of cake .
Norb

 

As usual you guys have good advice. Anyways, this is what happened. I pulled the headlights out and noticed that one side had the ground wire on the top prong of the 3 prong plug. The other side had the ground wire going to the right side of the plug, not the middle. Something definitely wrong here. I searched the internet and found all kinds of conflicting info. So I went to the source. Sylvania headlights. They were excellent. They had to call me back because the guy who knows the info wasn't in. He called back. He told me, looking at the light bulb prong (back of light) the top prong is the low beam, left prong is the ground and the right prong is high beam. So, checking my headlamps, the passenger side was incorrect. I went to the auto parts and purchased some three prong headlight plugs and redid the wiring and plug. The headlights work great and no more dim light when I check for continuity on the high beam side. I thought it was great that Sylvania did that. I went to several auto electric places and they couldn't even tell me what plug went where? They told me to use a jumper and play around with it. So, now that that's fix, I'm going to destroy it again by putting a couple relays in. LOL.... This info may be helpful in the future to someone. Hopefully. Thanks again everyone.

 

I'm glad that they had the plugs in stock! I don't know where I'd even go locally to try and find a replacement sealed beam bulb. I'm converting mine to H4 bulbs in conversion housings. The third day of our 2K mile trip home with the panel included 5 hrs after dark. I thought I was driving by candlelight after getting used to the projector lites in our Celica. "What can we do about these headlights, and how soon can we do it?" my wife asked after taking the wheel for an hour in the dark. We'll be pulling a 22' enclosed car trailer all over the country with Gracie so better lighting is a top priority.
56 EA, Take everything you have there on the left of the steering column and shove it up under the dash, attach some of the wires to a 6 glass fuse "block" that looks like something they got at radio shack, leave a bunch of the ends disconnected and bare and you have an idea as to what I'm facing. DEFINITELY going tear out that rats nest to do a complete rewire! I can't wait to get to it! The 18 fuse EZ wire kit is already here.

 

Just rereading some old post and thought I would mention that the headlight plugs for the aerostar (92-97 at least) are 9004/9007. My local parts house did not have a slot for the 9007 so upon some research I found the same plug is for both.