C3 Actuators

[Tom R.]

I'm attempting to diagnose a lazy-but headlamp and after rebuilding the vacuum pump, may have narrowed the fix to an internal diaphram on the actuator. I've checked hoses, vacuum from manifold to relay, tank, etc and all do their thing and properly. The 1978 generated 17-20 hg and loss is no more than 2-3 by the time it gets to the actuators.

When I engage vacuum pump to the red hose either side (with green vented) and pump, pump, pump it will pump to 20 hg and hold...no loss whatsoever.

However when I vent red and pump on green, the driver's side will pump up and headlamp flip open. In contrast on passenger's side with pump, pump, pump and pump...the headlamp barely comes up. I'm concluding the passenger's side internal diaphram is going bad which means replacing the actuator. Now, I've already replaced the external seal and boot so I know those are ok. Neither actuator with vacuum applied to green hose will show a reading although the headlamps either come up or begin to come up.

Am I concluding correctly here that the internal diaphragm is going and the entire unit must be replaced...or have I missed something? Anyone ever replace the internal diaphram or take an actuator apart?

Thanks

[ken sieloff]

Re: C3 Actuators

Check out Corvette Magazine online. The last online issue shows step by step how to rebuild the actuators with photographs to walk you through. The rebuild kits are available through Zip Products.

[Joe L.]

Re: C3 Actuators

Tom-----

If you've replaced the coned shaped shaft seal and that doesn't cure your problem, then I think that you've pretty well determined that the actuator is beyond help. These actautors are not otherwise serviceable. In fact, even the shaft seal replacement is an aftermarket "innovation". GM never serviced the shaft seals.

[Jack H.]

Could get lucky....

I know of a handful of guys who got 'lucky' with their actuators. They removed from the car, fault isolated to marginal internal diaphram (vs. front seal) and injected the self-vulcanizing tire repair compound bicyclists carry (available at most hardware stores). The sealing compound was injected into the actuator body and the diaphram exercised to work the sealer into the area of pin-hole leak, let overnight to setup and residual sealer flushed out with injected rinse water.

Two guys got 'lucky' with this attempt (cheap to try) because they actually HAD a main diaphram pin-hole instead of large rip or diaphram edge turned loose from actuator can's pie-plate crimp. Not a panachea, but can work cheap/quick in isolated cases....