headlights 71

[lyndon sharpton]

Ok guys I need help with my headlights on my 71 now. the lights will not come up when I pull the switch. it must be bad I hear a hiss comeing from it also when the lights are on when I pull the override under the dash one light will come up the driver side, the pass will not come up unless I get under the car a push it up. what is the best book to trouble shoot the system, an to adjust the system, I know I will need a new switch when you pull on it it also feels lose on the shaft an the dash lights are a touch an go as far as them coming on. how many switchs are under the dash on those cars? any thing you guys can tell me will help so much. thanks Lyndon

[george romano]

Re: headlights 71

I would check the actuator at the inop headlight first.

The hiss you hear is most likely the air passing THROUGH the switch to feed that leaking actuator.

George

[Jim T.]

Re: headlights 71

Lyndon the dash lights being a touch and go most likely is attributed to the piece of metal that slides on the reostat wiring in the headlight switch. The complete switch is not that hard to replace and the 71 service manual will help if you have one. From memory of doing a couple changes of the headlight switch I would loosen/remove the bolts at the base of the steering column where it enters the firewall. Remove the bolts securing the steering column under the dash and screws on the left and right. Support the steering wheel on the seat giving enough clearance to pull the dash corner down and change the switch. Remember where the vacuum hoses go on the new switch. You can go to Auto Zone and borow a hand operated vacuum pump and test for leaks in your headlight vacuum actuator. A person who posts on this board sells the headlight switches GM part number for about $50.00. Joe Ray Corvette parts.

[Jack H.]

Don't overlook the obvious!

I've seen quite a few owners drive into the shop with a replacement HL switch for installation because the vacuum headlights weren't working asking for switch installation. In the end, MOST of these situations turned out to be simple 'plumbing' problems with underdash vac lines having come loose from various control component nipples.

Understanding how the system works before you dive in to replace this/that 'faulty' component can save $$$. Many catalog shops sell a vacuum system trouble shooting booklet and Dr. Rebuild has vacuum schematic diagrams for each year car. Knowledge is power!

We just conducted a vacuum troubleshooting tech session at our NCRS Chapter and those who attended felt MUCH better about their ability to conduct 'care & feeding' missions with the 'beast' at home!

Bottom line, vacuum enters the cockpit from the back side of the check valve in the engine compartment routing though the firewall. Once inside the cockpit, that vac line routes in several directions via t-connectors. One side routes to the headlight door over-ride switch then on to the headlight switch and out to the headlight door control relays.

The opposite branch routes to the wiper door over-ride switch then to the wiper door actuator relay and out to the wiper door control relay. You can hear 'hissing' in the cockpit for a number of reasons and the noise could be associated with hoses that have become disconnnect, hoses that have ruptured, as well as vacuum switches that are defective (leaking).

So, why not check first to see if there's an easy fix (reconnect a disconnected hose) before assuming you have to replace a headlight switch?

[Mike S.]

Re: Don't overlook the obvious!

my 71 head lamps wouldnt work.i used avacuum gauage. first checked vacuum reading at vacuum port at intake. about 18 inches .then moved down to vacuum tank disconnected and blocked all lines but inlet an one outlet checked for vacuum drop had no drop ,18 inches .then connected headlamp hose vacuum to vacuum tank. vacuum drop about 10 inches.disconnected hose at headlamp relay.one with red stripe. connected gauage to hose. 18 inches vacuum.then conected gauage on headlamp accumulator vacuum droped 10 inches. so i had a bad head lamp relay. also had a bad brake booster .