1972 Manual Headlight Override Switch – CorvetteForum – Chevrolet Corvette Forum Discussion

1972 Manual Headlight Override Switch – CorvetteForum – Chevrolet Corvette Forum Discussion

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hello,

when i try to pull or push the headlight override switch under the dash it wont move and it won’t raise or lower the lights. the lights will go up and down when i pull the headlight switch though. any idea what could be causing this?

thank you.

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+61404532026, 11:43 pm

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originally posted by miccar

hello,

when i try to pull or push the headlight override switch under the dash it wont move and it won’t raise or lower the lights. the lights will go up and down when i pull the headlight switch though. any idea what could be causing this?

thank you.

the switch is designed to block vacuum on the small hose side. so if you pull it down and the lamps don’t open i’d have to say the switch is defective. you stated the switch won’t move…. it should if you pull hard enough.. (unless it’s down already and just not working, in that case push it up and see if it moves). remove the hoses from the switch, couple them together and then pinch off the hose with a pair of needle nose pliers.. if the doors open replace the switch.

or an even simpler test would be the remove the switch and pull it downward…. then try to blow through it… if it hasn’t blocked the switch then it’s defective.

now a quick fix… you can pull the **** real hard and it will pull apart.. then lubricate the o-ring that you’ll see with some grease, then re-install it.. i’d bet this will fix the issue unless the o-ring is bad.

willcox


last edited by willcox corvette; +61404532026 at 11:44 pm.

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+61404532026, 08:01 am

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good information.

could this keep the headlights from opening?

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+61404532026, 08:21 am

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hi len,

no.

when the stalk is pulled down the headlights open and remain open under all conditions. (regardless of whether the headlight switch is pulled or not.)

it really can’t prevent the headlights from opening when the headlight switch is pulled.

it does require that the headlight relays and actuators operate normally and that there is a vacuum supply.

regards,

alan

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+61404532026, 08:24 am

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thanks alan. this just started happening a week or so. i think i will put the new hose kit i have in to eliminate those possibilities.

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hi len,

replacing the hoses may seem to be a good idea but the chance of it helping anything is quite slim.

i’d think you could better spend your time by trying to make sure you have a good vacuum supply at the relays and actuators

you might need to check the headlight switch…. since it controls both relays and both actuators and since neither side is opening it could be the switch.

have you done anything to the car recently that may have caused this problem?

have the headlights been working normally?

did you do any work under the dash or up by the headlights that may have dislodged a hose?

if you want to check the hoses you can actually just cut about 3/8″ off the end of each one and put it back in place. this gives the hose a ‘fresh’ sealing surface…. and accomplishes just about everything a new hose set does.

regards,

alan


last edited by alan 71; +61404532026 at 09:03 am.

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+61404532026, 11:15 am

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actually they close just fine. i haven’t change anything on the care in the last couple of months.

id they close when i turn off the headlight at the swith that would means they are getting vaccum correct?

then the problem would be on the opening side?

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+61404532026, 02:31 pm

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if the lamps open and close when you pull the headlamp switch the system is working fine and your problem is probably just the over-ride vacuum switch itself.

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+61404532026, 02:45 pm

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the opening part is the problem. they close with no problem.

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+61404532026, 04:44 pm

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originally posted by lenwoodruff

the opening part is the problem. they close with no problem.

originally posted by miccar

hello,

the lights will go up and down when i pull the headlight switch though.

thank you.

now i’m confused… when you pull the headlamp switch do they open?

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+61404532026, 05:37 pm

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originally posted by willcox corvette

now i’m confused… when you pull the headlamp switch do they open?

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so your headlights go up and down with the headlight switch? correct?

and your headlights don’t go up or down (or just up or down) using the override switch under the steering column? correct?

just trying to sort out your problem so we can figure it out.

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+61404532026, 05:38 pm

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mine won’t open with the headlight switch or the overide switch under the dash.


last edited by lenwoodruff; +61404532026 at 05:38 pm.

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+61404532026, 05:55 pm

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hi len,

would you consider reversing the 2 large hoses (red and green stripe) that run from the relay to the actuators?

if the headlight now opens but won’t close you’ll know you have a relay problem. red to the rear of the actuator… curved pipe, green to the front of the actuator… straight pipe.

you can reverse the hoses either at the relay or the actuator.

it’s odd that they both were working and now both won’t close.

what year is your car?

does it have one or two headlight relays?

regards,

alan

this is a 71,

a relay for each actuator.

2 large hoses running from the relay to the actuator.

the large hose in the center of those 2 is the vacuum supply to the relay.


last edited by alan 71; +61404532026 at 05:56 pm.

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+61404532026, 06:18 pm

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mine is a 78 and has 2 relays.

i used a vacuum pump on the green hose and the lights will rise up.

there is another small hose that t’s off to each relay. it has vacuum when the headlight switch or orveride is closed but no vacuum when either are in the on position?

so how does the relay get the signal to send vacuum to the red or green hose for opening & closing?


last edited by lenwoodruff; +61404532026 at 06:19 pm.

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+61404532026, 06:46 pm

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hi len,

the relay receives the vacuum (control) signal through that small hose.

the small hose should be attached to the short straight pipe on the side of the relay’s can.

the headlight vacuum system has 2 sides:

control…. filter, check valve, headlight switch, over-ride valve, relays, small hoses.

servo…. large hoses and actuators.

the control system signals the actuators to open or close.

regards,

alan

the ‘fail’ position for the headlight is open. no vacuum….headlights open.

that why pulling the override down should open the headlight doors.

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+61404532026, 11:44 am

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thanks alan. last night i switched the red & green hoses while the engine was running but the door didn’t open.

i thought i would drive it a little bit today to see if after i added some new supply hoses the headlights would open.

it just just mysterious that both doors stopped working at the same time. to me that would rule out the relays wouldn’t it?


last edited by lenwoodruff; +61404532026 at 11:44 am.

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+61404532026, 11:55 am

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originally posted by lenwoodruff

thanks alan. last night i switched the red & green hoses while the engine was running but the door didn’t open.

i thought i would drive it a little bit today to see if after i added some new supply hoses the headlights would open.

it just just mysterious that both doors stopped working at the same time. to me that would rule out the relays wouldn’t it?

using this guide test each component and you will find the problem.

http://www.corvette-101.com/vacuum.htm

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+61404532026, 06:42 pm

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originally posted by peterbuilt

i have that printed out. i will take a look through it again.

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+61404532026, 10:31 pm

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i suspect that the hoses are not routed correctly to the manual override switch or between it and the headlamp switch.

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+61404532026, 07:35 am

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i would agree except nothing has been touched on the vacuum lines in many years and these were working a couple of weeks ago.

i tested the control line from those switches and there is vacuum when they are off and no vacuum when they are on.

the odd thing if the relays are the issue is that they both failed at the same time. i could see one failing but both is weird.


last edited by lenwoodruff; +61404532026 at 08:04 am.

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