rbat

After replacing all the hoses and confirming they are installed correct and trying three different switches, the headlights will not go down by the headlight switch (unless I pull the release under the steering column). It is a 1975
thanks in advance for the help

7T1vette

Vacuum leak(s) in hoses, cracked hose(s), leak in tank, low vacuum level from engine (10" Hg or less) are possibilities.

But, the most likely problem is that the vacuum relay(s) that direct vacuum to the headlight servos has internal leakage. You can test this by bypassing them altogether.

The Yellow striped hose is the main vacuum supply going to the center nipple on the relay. Pull that hose off the relay and run it to the headlight servo (either UP or DOWN). The light bucket should respond quickly, if the light switch is ON and override is not pulled and if you have adequate vacuum level. {Note: If you have a relay for each side, you may want to remove that Yellow-striped hose from the other relay and block it off during this test.} If that works OK, then run that hose to the other nipple on the servo to see if it works OK in the other direction. Then do the same testing for the other headlight.

When done with this test, you should know if your vacuum level is adequate and if the vacuum relays need replaced. I have actually come up with a method of refurbishing original units...as long as the shuttle valve (inside) is merely worn...but not deteriorated. However, I'm not sure the effort to achieve that solution is justified when you can buy a new one for about $60.

scottyp99

If they worked fine before, and you replaced the hoses, and now, suddenly they don't work, you don't have to be a rocket surgeon to put 2 and 2 together and get 4. My first instinct would be to re-check the hose installations. Here is a link that should help you out if you don't already have it.

http://forums.corvetteforum.com/c3-t...tem-works.html

Edit: Wait a minute, you say you pull the little **** under the steering wheel to get them to come down? That's supposed to make them stay up. You may have something hooked up backwards.


Scott

Alan 71

Hi r,
In 71 the hose hook-up to the dash headlight switch was shown incorrectly in the AIM, and elsewhere. Depending on what schematic you followed to check the hose locations, you might have hooked them up incorrectly.
The BLUE striped hose coming from the bottom nipple on the over-ride switch connects to the FRONT nipple on the headlight switch.
Could that be your problem?
Regards,
Alan

rbat

I should have been more clear... the car was in pieces so I do not know if they worked before. Also, I tried reversing the hose connections but I will try again to be sure.
thanks

jsholm2

These are great instructions. I'm pretty sure this is what I used when I reworked my vacuum and light system. I would also check the valves under the dash as well (you may have already done this). If I remember correctly, there is one on the (drivers side interior)and one in between the two actuators (exterior). I would also replaced all my springs with a stainless steel set from covette central or ecklers. Sometimes these rusty springs can cause issues, however I doubt that is the problem if the lights open properly.

Easy Mike

The override should not be open.