74 runs "different" when headlights are on
10-10-2020, 09:41 PM
#21
Le Mans Master
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2022 C3 of the Year Finalist - Modified
Cruise-In VIII Veteran
Maybe, the replacements just are not the quality of the originals.
10-11-2020, 10:08 AM
#22
Safety Car
Thread Starter
10-13-2020, 06:46 PM
#23
Melting Slicks
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Have you verified that the vacuum motors hold vacuum on both sides? The seals around the operation shaft are well known for leaking and such only happens when the doors are up. Even though the doors mechanically lock in the up position via hyperextension of the mechanism vacuum is always applied to the front side when the engine is running and doors up. Vacuum is always applied to the back side of the motor when the doors are down but since there's no shaft seal at the rear leaks are less likely.
Someone before said there is a "controlled vacuum leak" in the headlamp door system. That is not true. Both the headlamp and override switches close the vacuum side and expose the other to the atmosphere in on position and allow vacuum to pass in the other. This allows the springs inside the relays to move the "dogbone" to the opposite position. Except perhaps for a brief moment when the vacuum switches move from one position to the other the vacuum portion of the system is never exposed to atmosphere thus no vacuum leak be it "controlled" or otherwise. The only system (I'm not talking PCV) in our cars that does use a controlled vacuum "leak" is cruise control. I put "leak" in quotes because you can't leak vacuum to the atmosphere--you can only leak atmosphere to vacuum.
Someone before said there is a "controlled vacuum leak" in the headlamp door system. That is not true. Both the headlamp and override switches close the vacuum side and expose the other to the atmosphere in on position and allow vacuum to pass in the other. This allows the springs inside the relays to move the "dogbone" to the opposite position. Except perhaps for a brief moment when the vacuum switches move from one position to the other the vacuum portion of the system is never exposed to atmosphere thus no vacuum leak be it "controlled" or otherwise. The only system (I'm not talking PCV) in our cars that does use a controlled vacuum "leak" is cruise control. I put "leak" in quotes because you can't leak vacuum to the atmosphere--you can only leak atmosphere to vacuum.
10-14-2020, 10:03 AM
#24
Safety Car
Thread Starter
Have you verified that the vacuum motors hold vacuum on both sides? The seals around the operation shaft are well known for leaking and such only happens when the doors are up. Even though the doors mechanically lock in the up position via hyperextension of the mechanism vacuum is always applied to the front side when the engine is running and doors up. Vacuum is always applied to the back side of the motor when the doors are down but since there's no shaft seal at the rear leaks are less likely.
Someone before said there is a "controlled vacuum leak" in the headlamp door system. That is not true. Both the headlamp and override switches close the vacuum side and expose the other to the atmosphere in on position and allow vacuum to pass in the other. This allows the springs inside the relays to move the "dogbone" to the opposite position. Except perhaps for a brief moment when the vacuum switches move from one position to the other the vacuum portion of the system is never exposed to atmosphere thus no vacuum leak be it "controlled" or otherwise. The only system (I'm not talking PCV) in our cars that does use a controlled vacuum "leak" is cruise control. I put "leak" in quotes because you can't leak vacuum to the atmosphere--you can only leak atmosphere to vacuum.
Someone before said there is a "controlled vacuum leak" in the headlamp door system. That is not true. Both the headlamp and override switches close the vacuum side and expose the other to the atmosphere in on position and allow vacuum to pass in the other. This allows the springs inside the relays to move the "dogbone" to the opposite position. Except perhaps for a brief moment when the vacuum switches move from one position to the other the vacuum portion of the system is never exposed to atmosphere thus no vacuum leak be it "controlled" or otherwise. The only system (I'm not talking PCV) in our cars that does use a controlled vacuum "leak" is cruise control. I put "leak" in quotes because you can't leak vacuum to the atmosphere--you can only leak atmosphere to vacuum.
10-14-2020, 10:12 AM
#25
Melting Slicks
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Yes, the front connection of the actuators/vacuum motors. The rear connection will only reveal leaks in the diaphragm, its' seal or the metal body itself. You have to check the front connection to test the seals around the shafts. Fortunately new shaft seal kits are easily available, cheap and good quality. If you replace just be sure that the shaft is perfectly clean, completely free of corrosion, pub black tape around the threads at the end and lube everything with silicon grease. This ensures that the new seals won't be scratched during installation and maintain their seal as the shaft moves through them.
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