Headlamp Cover: Testing and Inspection

Headlamp Covers-Standard
















The headlamp covers are opened and closed by two vacuum motors. Refer to Figs 1, 2 and 3 for location of the headlamp cover operating components and installation. Note the vacuum hose routing, connections and color codes.

The headlamp switch, when pulled full out actuates a distribution valve, located on the back of the headlamp switch. The distribution valve applies vacuum to the vacuum motor operating the headlamp covers. The distribution valve also provides a vacuum relief (exhaust) port to that side of the vacuum motor diaphragm to which vacuum is not applied.

When the headlamp switch is pushed in to turn the headlamps off, the vacuum supply and relief positions of the distribution valve are reversed. This subjects the opposite side of the vacuum motor diaphragm to engine vacuum, and also vents the vacuum at the opposing side of the diaphragm to atmospheric pressure. The vacuum motor closes the headlamp covers.

A reserve vacuum reservoir provides vacuum storage, which permits limited cycling of the headlamp covers without the vehicle engine running.

A check valve is used in the vacuum source line, to prevent vacuum from leaking from the reservoir back through the engine.

Springs are used on all models to automatically open the covers, in the event the system should lose vacuum. The spring is built into each motor. Vacuum applied to the vacuum motor diaphragm during closing overcomes this spring tension.

If the headlamp covers will not open automatically, a bypass valve is provided, to vent the system and allow the covers to open. The valve is located in the vacuum lines near the reservoir and the left-hand front fender.

If the engine is shut down for a minimum of 18 hours, a normal system leak would allow the covers to open under the spring force.

TESTING

Headlamp Cover Vacuum System Leak Test

A leak test or any part or component of the headlamp cover vacuum system, can be accomplished with the use of the vacuum test probe. (Refer to Vacuum Test Probe for fabrication.) To perform the leak test, plug the probe into the system at the desired point. The reading on the gauge should momentarily fall below the preset value of 14 inches of vacuum. If there are no leaks in that part of the system being checked, the gauge reading should come back to 14 inches of vacuum and hold steady. If a leak is present in the system, the gauge reading will not come up to 14 inches of vacuum.

The leak test for the headlamp switch can be accomplished by attaching the vacuum test probe to the center (white) part of the headlamp switch and capping the two outside ports. Move the switch selector through the Off-Part-On position, and observe the reading on the vacuum probe gauge. The gauge should read 14 inches of vacuum in all of the positions. If the reading should fall off at any of the positions, the headlamp switch should be replaced.

Vacuum Test Probe

A vacuum gauge is required to diagnose and test a vacuum control system. The vacuum test Tool T77L-9510-A or equivalent, is recommended. It is also recommended that the vacuum gauge be used, as a part of a vacuum probe test. Ordinarily, a vacuum gauge is used alone to measure the vacuum from a vacuum system hose or nipple, reservoir, or the engine intake manifold. A vacuum probe tester, on the other hand, is used to supply a definite amount of vacuum to a particular point in the system. It tests the system from this point to a component.

A vacuum probe tester is not commercially supplied, but it is easily made.

1. Cut or splice a length of 3/16-inch hose, long enough to reach from the engine intake manifold to the most remote component in the vacuum system. Call the ends of the hose the manifold end and the working end.
2. Insert a 4-way connector into the working end of the hose.






3. Attach a vacuum gauge to one of the 4-way connector nipples (Fig.3).
4. Install a short length of 3/16-hose with an adjustable hose restrictor on another nipple of the 4-way connector.
5. Install a short length of hose on the last nipple of the 4-way connector. Insert a tee connector into this hose.
6. Install a short length of hose to the two open ends of the tee connector (Fig. 3). Install a 3/16-inch and 1/8-inch reducer in one hose, and a 3/16-inch splice connector in the other hose. By adding or removing connectors (splices) to these test probe hoses, they can be connected to any 3/16-inch-1/8-inch hose nipple, or connector, while the other test hose is plugged, or both the 3/16-inch and 1/8-inch tester probes (Fig. 3) can be used at the same time.

To adjust the probe to the required 14 inches of test vacuum, plug the test probe hoses into the vacuum source at the carburetor, and adjust the hose restrictor, until the vacuum gauge reads 14 inches. The vacuum supply at the end of the test probe hoses should be checked often, as the engine warms up, loads up, etc. Headlamp Covers Will Not Open

1. Turn on the headlamp switch.






2. Turn the bypass valve to the vent position. If the headlamp covers have opened, check the hoses and connectors between the bypass valve and the headlamp switch for kinks and obstructions (Fig. 3).
3. If kinks or obstructions are encountered, service or replace as necessary.
4. If no kinks or obstructions were encountered, replace the headlamp switch.
5. If, after activating the headlamp switch and turning the bypass valve to the vent position, the headlamp covers remained in the closed position, check the mechanisms for binds.
6. If a binding condition exists, replace or service the damaged part.
7. If no binding condition is encountered, check the hoses and connectors between the bypass valve and the vacuum motor(s) for kinks and obstructions.
8. If kinks or obstructions are present, service or replace as necessary.
9. If no kinks or obstructions are found, replace the bypass valve.

Headlamp Covers Will Not Close

1. Check the bypass valve by turning it to the normal position, and placing the headlamp switch in the Off position.
2. Check for leaks and kinks or obstructions through the check valve from the intake manifold.
3. If any irregularities are found, service or replace the hose between the intake manifold and the check valve.
4. If no irregularities are encountered, disconnect the reservoir hose at the check valve. Check the hose and reservoir for leaks.
5. If leaks are found, replace or service as necessary.
6. If no leaks were found, check the valve port that connects to headlamp switch for vacuum and leaks.
7. If a leak is found, replace the check valve.
8. If no leak is found at the check valve port, check the valve port that connects to the headlamp switch for vacuum and for leaks.
9. If a leak is found, replace the check valve
10. If no leak was indicated check the headlamp switch, hoses, connectors and motors in the open circuit (green hose) for kinks or obstructions.
11. If kinks or obstructions are found, replace or service as necessary.
12. If no kinks or obstructions are found, check for leaks or obstructions at the headlamp switch, hoses, connectors and motors in the close circuit (yellow hose).
13. If leaks or obstructions are found, service or replace as necessary.
14. If no leaks, kinks or obstructions were found, check the headlamp cover mechanism for binds and replace or service as necessary.