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I've been trying to diagnose a headlight problem where one headlight comes up but the other doesn't. Following the Willcox testing video I used a handy vac to test raising and lowering both. On the one that won't come up, it doesn't raise when using the hand vac connected to the inlet. However if I manually raise the headlight then using the handy vac does work to lower the headlight, and when it's lowered then the handy vac will hold pressure too.
I thought if a vacuum seal was broken that both up and down would fail under vacuum. Any ideas on what to check before I try to replace the whole unit?
Thanks! Didn't realize there were two separate seals, one front and one back. The behavior seems pretty clear that the seal is broken and needs to be repaired. I plan to follow
Yes, the headlamp door vacuum motors are bi-directional. There's a rubber membrane inside (in the middle) and shaft seals around the operating shaft at the front. The shaft seals only come into play when raising; the inner membrane is used for both raising and lowering. Even though the doors physically lock into the open position and gravity would keep them from rising on their own vacuum is always applied to one side or other whenever the engine is running.
Make sure that the shaft is scrupulously clean and smooth before installing the boot. Also cover the threads at the end of the shaft with black electrical tape or similar and apply some silicon grease.
The control and operation sides of the system are separate excepting at the vacuum relay(s). The control side has no vacuum reservoir thus the tiniest leak (often at a relay) causes the doors to "wink" when starting the engine.
Original vacuum components are very long-lasting but the current Chinese made replacements are such utter junk that I can't believe the vendors still sell them.
You can swap the lines going to the relays and see if the issue moves to the other light or stays where it is. That way you may be able to make a better guess at where to look (of course it could be both....)
You can swap the lines going to the relays and see if the issue moves to the other light or stays where it is. That way you may be able to make a better guess at where to look (of course it could be both....)
You can 'direct feed' vacuum to the big actuators by plumbing the yellow striped hose going to the center tap on the relay directly to one side and then to the other side of the actuator. That will connect manifold vacuum to the 'up' and then the 'down' side of the actuator to see how the bucket operates WITHOUT the relay in the system. If it works properly with test on each side, the actuator is NOT your problem and the relay you 'bypassed' needs replacement. I don't know of anyone who actually repairs them.
If it does NOT work properly, make sure your engine's vacuum level is at 14'" HG or more. If vacuum is OK, your actuator does need repair. There are kits for replacing the seals in the actuator, or you can just replace it. If vacuum is not adequate, THAT needs to be resolved before you do anything to the headlamp or wiper door (if you have one) or to the HVAC control system.
Last edited by 7T1vette; Aug 27, 2020 at 12:09 AM.
Headlight vacuum problem
