My 1965 head lights only work when the high beams are turned on. I replaced the light switch with the same results. Any help would be greatly appreciated.

 

Most likely problem is the dimmer switch on the floor. The switch portion that feeds the low beams isn't working or the connector on the wire is loose, broken or corroded. You can buy the dimmer switch at most local auto parts stores very reasonably and it's held in by two screws and has a connector with three wires. The tan wire is the wire that feeds the low beams. The headlight switch cannot cause the problem because it feeds the same 12v to the blue wire on the dimmer whether in bright or dim position. You may want to hold on to that old headlight switch, you may find it works better than the replacement if it was original equipment switch.
If you pull the plug off the dimmer and short the blue wire to the tan wire and the dims come on, the dimmer switch is the problem. If not your problem is up front. (Two bad bulbs, a broken or disconnected tan wire on the drivers side connector will kill both dim beams) Another good way is to measure the tan wire with a voltmeter when the switch is pushed to dim with the headlights on.. If it's zero, the switch is bad.

 

Giulio - Welcome to the Corvette Forum. As you already heard, the dimmer switch is the prime suspect and should be an easy fix.
Tell us about your 65 Vette, we do like pics.
Mike T - Prescott AZ

 

I picked up the car summer of 2022 from a retired shop teacher that was only selling because of bad knees, his wife told us it tock him 2 years to finally decide to sell. We hit it off right from the beginning and still keep in contact. It's a driver convertible 327 4 speed with side pipes not original motor but it has been rebuilt and runs strong. We removed the dash freshened up the paint and gauges. After reinstall the dash 3 times (getting good at it lol) had a grounding issue and the trip cable got very hot. Thats when the head light issu e started everything else is working. I will try the dimmer switch first. Question why do they call it a dimmer switch?

 

It dims from bright, 4 headlights to two low beam lights. I realize most people drive on low beam, Dennis

 

You do know that there’s a switch on the floor you press to change from bright do dim, correct?

 

Yes, my situation is that the driving lights only come on when the dimmer switch is turned on, that's when all 4 lights are on.

 

It's not an off and on switch. It's a switch between dim and bright. Do the troubleshooting I gave you earlier. It's most likely a bad switch (very common), but could also be a bad or burned connection in the places I told you.

 

What do you consider “driving lights”? The full headlights? Or the parking lights that double as turn signals?

the floor-mounted “dimmer switch” does not have an on/off position, It only has high beam/low beam positions.

As noted previously, there should be a switch on the floor, on the left

Pull the headlight switch out fully, and then push on this switch with your foot, and each time you push it, it should cycle between high ( four lights) and low beam ( two lights). There is no “ off”, although broken switches or corroded connections can cause malfunctions.

 

Thank you I just picked up a new switch today and will be installing it tomorrow hopefully it will work. What I ment by driving lights was light switch pulled all the way out. I will let you know tomorrow how it goes.

 

You could save yourself time and money if you'd troubleshoot instead of parts swapping. The headlight switch was not a possible problem. The dimmer switch is, but it may not fix it. When you ask for help, you should at least try to troubleshoot before you swap parts. Sometimes when you switch parts you introduce new issues or temporarily hide old ones. Your money, your, time, your choice. Too many people who ask for help really are asking what part to buy. These are small amounts of money, but one day it could cost you big.

PS. You can tell if the switch will fix it by pulling off the connector and placing in on the new switch before you remove the old one or install the new one. It's possible if you do that you'll find a disconnected or corroded wire in the connector, too.

 

I tested voltage at the dimmer switch and got the following
light switch all the way out
green to blue 12.5v
No voltage green to beige or blue to beige
At the head light connection
switch pulled all the way outNo voltage
Dimmer activated all 4 lights are on
Green to tan 10.56
Black to green 10.56
​​​​​

 

Sorry, I'm having trouble picturing where you are measuring.
You will only have voltage on ANY of the three wires on the dimmer switch when the headlight is pulled to headlights on. In that condition, you will always have battery voltage on the blue wire at the dimmer switch (it comes directly from the blue wire on the headlight switch)
Then you will also have battery voltage on either the green wire, or the tan wire depending on whether the switch is clicked to bright or dim. The green wire feeds all four bulbs filament for brights only when the dimmer is clicked to bright, the tan wire feeds only the two outside bulbs dim filaments, but ONLY when the dimmer is clicked to the dim position. At no time should there be voltage on all three wires. It should always be on the blue when the headlights are ON, but not when they are off.
Put your negative meter lead on a good ground, pull on the headlights and touch your positive meter lead to the blue wire on the dimmer. It has to be there or your brights wouldn't work either. Then, if the connector is still on the switch touch the positive meter lead to the green wire, it should read battery voltage when the dimmer is in the bright position. That also has to be working with the symptom you described. Now this is where you're troubleshooting helps, you should put your positive meter lead to the tan wire and push the dimmer switch down till it clicks, the voltage should switch from the tan to green and then back to the green with alternate clicks, voltage to tan in dim and voltage to green in bright. If you have the connector off the dimmer switch, just save all that and short the tan wire to the blue wire. If the two outside dim bulbs come on now, the switch is bad. If they do not, the problem is in the wiring toward the front of the car. All you're doing with the dimmer switch is directing the voltage from the headlight switch blue wire to EITHER the tan or green depending on whether the dimmer is making contact with that particular click of the dimmer.

 

Thank you I will give all these a try in the next few days. Re the dimmer switch do I pull up on the connector just enough to get tester prob on the tabs?

 

You can, if the probe won't fit down beside the wire in the connector, but at this point you can just short the blue to the tan with the connector off and see if you get the two dims. If you already have a new dimmer, just plug it in and see if you have lights on bright with one click and dim with another click. I was just trying to get you to determine if the problem was in the dimmer or in the wiring going forward. We need to eliminate the dimmer as a problem first, because it's the most common.

 

Thanks again were are busy tomorrow but will be out in the garage on Thursday

 

Update tried to jump blue to beige at first and nothing happened than when I wiggled the wire in the socket of the beige the low beams worked. I reconnected to the dimmer making sure there was a good connection and also removed and sprayed the under hood electrical connection points with electrical contact cleaner. Very glad to say everything is working correctly. Thank you.

 

The more you exercise that dimmer the better it will work, the contacts will corrode when you don’t use it for a while. If it gives you any more trouble, check that connector in the plug at the dimmer very carefully see if the wires sre burned in the connector.

 

Edit... I must've replied to a "similar thread" by accident. Sorry gents....

This is a 63 Dimmer Switch(see attached) so you can see what the internal contact mechanism looks like, which is similar to the earlier versions. It's a rotating contactor inside the housing.

I've repaired both types in the past. Replacements maintain function but have different visible external features. I like to restore vs replace when possible.

Rich
Edit... the video in the pdf is broken for some reason. View here....

 

since (most) everyone normally drives with the dims on, shouldn't it be called a brighter switch?.....lol!