Head light vacuum question
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Intermediate
Joined: Nov 2016
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Head light vacuum question
Can the head light vacuum source come from the vac port on the carb or does it have to come from the intake port? My headlights wont open and I have the line going to the carb. Im thinking this might be the problem. Just looking for opinions before I start doing vacuum testing on the components.
I went to the carb because I dont have room for the vac line on the intake port. Ill have to get a new intake fitting if this is the problem. Thanks Ken
I went to the carb because I dont have room for the vac line on the intake port. Ill have to get a new intake fitting if this is the problem. Thanks Ken
Is my vette stock?? HAHA
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What year is your car. It has to be coming from a manifold vacuum port on the intake so its a constant source. I guess if you dont have a choice you could use manifold vacuum under the carb.
it should be goiing to a reservoir so it has a good supply at low rpm. It also has to have a one way valve so that it maintains the vacuum. You should have 2 hoses, one that is the switched source form the headlight switch and the other to actually do the openning and closing.
it should be goiing to a reservoir so it has a good supply at low rpm. It also has to have a one way valve so that it maintains the vacuum. You should have 2 hoses, one that is the switched source form the headlight switch and the other to actually do the openning and closing.
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Most of the vacuum operated sub-systems are connected to vacuum at the vacuum [supply] reservoir. That tank is supplied by the intake manifold thru a one-way check valve, so that vacuum level will be relatively stable, rather than at manifold vacuum level which varies with throttle position. The exceptions are the vacuum brake booster (cars with power brakes), which has its own one-way check valve, and the components which are intended to sense throttle position via vacuum level: vacuum advance on the distributor, vacuum modulator on some automatic transmission models, and any vacuum switches that require manifold vacuum.
If your headlamp mechanisms operate slowly...or not at all..., the most likely source of your issues is at the headlamp vacuum relay switch/es. You should NOT connect the headlamp actuators to the carb, as any leakage in that system will yield unwanted idle quality problems. You need to sort out the defective component/s in the headlamp vacuum system and keep that system connected to the vacuum reservoir.
If your headlamp mechanisms operate slowly...or not at all..., the most likely source of your issues is at the headlamp vacuum relay switch/es. You should NOT connect the headlamp actuators to the carb, as any leakage in that system will yield unwanted idle quality problems. You need to sort out the defective component/s in the headlamp vacuum system and keep that system connected to the vacuum reservoir.
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Intermediate
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My Vette is a 79. I guess im going to hook the brake booster to the vac port on the back of the carb and put the headlight vac to the manifold.
7T1vette, You mentioned the vac mod on the auto trans. Can that be hooked up to the vac port on the front of the carb?? Right now I have it hooked to the intake vac port.
Thanks Ken
7T1vette, You mentioned the vac mod on the auto trans. Can that be hooked up to the vac port on the front of the carb?? Right now I have it hooked to the intake vac port.
Thanks Ken
