72 Corvette newbie

I'm not sure, but I may have bumped something when trying to get my wipers working again or when looking into replacing the aftermarket radio with a factory unit.

I couldn't figure out why my wipers weren't working and was looking for a loose connection under the dash after doing investigation about radio replacement (back to stock radio) ... after consulting the service manual I realized there was a over-ride switch under the steering column for servicing the wipers and had inadvertently turned them off.

Under the dash there are 2 vacuum controls, one for the wiper cover and the other I don't know what it does and I don't see anything in the manual, and I can't find anything in my service manual for it ... it doesn't seem to do anything regardless of the position.

When I started the engine to test my theory about the wiper over-ride switch the headlights popped up even though I hadn't turned them on and now they won't go down.

Also, now when I shut off the engine there is a hissing noise on the drivers side like a vacuum reserve is draining and the wiper cover pops up ... but I can't find a loose hose and it stops hissing before I can find anything ... any ideas what I may have done?

Easy Mike

The second vacuum switch under the steering column is the headlight over ride. Works the same way as the wiper door over ride.

Alan 71

Hi 72,
When the vacuum over-ride on the left side is pulled down the headlights should open, but not illuminate.
If you were to then pull the headlight switch **** the lights would illuminate.
The headlights will shut off but not close when you push the headlight switch **** back in… they won't/can't close as long as that over-ride switch is pulled down. Push it back up and the headlights close.
The purpose is to be able to have the headlights up, but not illuminated …. in order to change a headlamp for instance.
Regards,
Alan

NewbVetteGuy

Wow. I had no idea these override switches existed! -Are these on all C3s or just a certain year range?


Anyone (and by that I mostly mean Alan) have a good picture of these things? ;-)


I've got a set of LED Halo headlights now and I was thinking of having them be always-on (just the halo part) like daytime running lamps - but I haven't stopped to think of how to make this work with the simple on/off stock headlight switch. Now I'm thinking I could just wire the halos to be on when the key is on and use the headlight override switch to pop up the headlights on demand- even when the main beams themselves are off...


Adam

Alan 71

Hi,
On 68-72 cars there were 3 controls:
right…. pull down to open wiper door
center… turn to stop wipers on windshield
left…. pull down to open headlight doors.
Regards,
Alan

72 Corvette newbie

That's kind of what I thought ... the headlights do come on when I pull the switch and go off but the headlights stay up ... I've had the vacuum over-ride **** in both positions and they don't do anything ... I've tried it with the engine running and shut off ... I've even tried pulling the vacuum lines off the actuators and they still don't respond and while I see electrical wiring in the service manual that I have I don't see anything for the vacuum lines ... my manual did have a diagram for the vacuum lines for the wiper cover which was how I discovered the over-ride for the wipers.

BTW Alan, I did order an AIM to go along with my service manual as you recommended with my radio problem, but it won't be here for another week or so. Being that I like to do what I can myself I'm sure it will come in handy ... and for those things that I can't do, my mechanic will be appreciative of my having it too!

Alan 71

Hi 72,
If you're hearing a hiss a hose is displaced.
Here's the vacuum hose routing for both the headlights and the wiper door.
You can see and access SOME of it, but it's pretty difficult with the drivers-side dash in place.
You might see something though.
Regards,
Alan

There's a well documented error in this drawing…. the light blue striped hose should be on the FORWARD pipe on the headlight switch, not the rear pipe.

72 Corvette newbie

Thanks again Alan, all the hoses I could see and then I gave a gentle pull on the hose with the light stripe going up to the headlight switch ... It fell free. Just about then the wife said it was time for dinner. I tried to reach up to the switch but couldn't find it ... I'll try again tomorrow. Do you have any advise or is it pretty easy to get to? While I'm there I have the part and need to replace the ****/shaft too

Alan 71

Hi,
Getting to the head-light switch isn't easy…. in fact it's difficult. Access to the switch on a car with a/c is even more involved

Some folks suggest loosening the 2 bolts that support the steering coumn tat are right below the dash pad and the 2 bolts at the firewall. This will let the steering column drop about 2 or 3 inches. It's wise to still support the column in some way so there's not undue stress on the column at the rag joint.

You then remove the 7 screws that hold the dash pad in place. The pad can then be pushed down and rearward about 2 inches which lets you just reach the hose connections.

A NASTY job at best, because the is SO MUCH going on behind the dash pad.

Be very careful that you don't break something or disconnect something else while you're doing this. I'd wait until you have the AIM which may help you understand what all is going on behind the pad.
Good Luck!
Regards,
Alan

This is the access you're trying to achieve. You can see the 2 hoses running to the switch.

Sluefoot

I had the same problem on my '79....headlights wouldn't go down....BUT...I had just replaced the speedo cable...SO....I looked in that same area, and the vac. line to the light switch had fallen off....so I knew I couldn't reach up far enough (I don't have ac) to put it back on, so I grabbed the FUSE REMOVAL/INSTALL tool for removing fuses in elect. boxes....it's about 7" long, and the small end of the tool has the opening for the smaller fuses....JUST RIGHT for holding the vac. line...and successfully putting it back on the light switch.......didn't have to tear dash apart!
Sometimes ya' just gotta step back, take a "out of the box" approach, & figure out how to do some of these things WITHOUT a helluva lotta extra work!!

72 Corvette newbie

Thanks guys ... Unfortunately(in this case) I do have A/C

Alan, your advice has helped in the past so I think I'll take it again and wait until the AIM gets here to take it apart, besides I'm really not looking forward to it!

Why 'o why couldn't it have been the other end?

Easy Mike

Yes. All C3s have a head light over ride vacuum switch. 68-72s also have a wiper door over ride switch.

Have you not seen the over ride on your car?

Alan 71

Hi 72,

"Why 'o why couldn't it have been the other end?"

Because on occasion the fix will be easy…. but when dealing with the Corvette dashboard it RARELY is!
Regards,
Alan

72 Corvette newbie

Just an update to kind of close out this thread, I was kind of stunned when the mailman dropped off my AIM this morning ... On Memorial Day!


Anyway, I pulled the dash down and out enough to get to the back of the switch and got the vacuume hose back on, I got everything back together and the headlights, once again, go down!

Later when I drove it this afternoon, the speedometer wasn't working ... the cable had came loose and the clip that holds it on was laying on the floor ... I had a heck of a time getting my hand up there, even after taking the a/c duct out, then getting the cable straight but it finally snapped on!

Having the Assembly Manual is so much more help than the service manual, thanks again Alan for recommending it!

Alan 71

Hi 72,
I'm pleased you found the AIM helpful AND that you got your problem taken care of.
The Chassis Service Manual is a help for certain things the the AIM doesn't contain.
Regards,
Alan

george2066

anything to do with dashpad, bezels, shifter plate, side coverings make me cringe, let alone that fuse block wayyyy up in there