1968 Vette Wiper Door Pops Up

[Jeff H.]

I joined NCRS five days ago. I've owned a '68 327/300 for the past 45 yrs. Has 56k miles. It's been in storage off/on for close to 30 yrs. Have been doing restoration work both inside/out past couple of yrs. Car runs well. A problem that recently surfaced is the wiper door has opened and closed when I'm driving. Does so on random occasions not every time I'm driving. Read other threads about wiper door issues but haven't found one with same issue a mine. Have contacted several corvette parts outfits and told it could possibly be an issue with wiper door vacuum control solenoid, wiper door limit switch, or wiper override switch. Interested in obtaining feedback from owners who may have experienced the same issue and what was done to correct the problem. Thank you!

[Anthony F.]

Re: 1968 Vette Wiper Door Pops Up

Could also be a problem with the vacuum canister. Check this link:

https://www.forums.ncrs.org/showthre...886#post803886

It's not exactly the same problem, but, you never know...

Quote from a friend of mine: "Whoever invented the vacuum system for the C3 Corvette's was either a genius or totally insane".

[Jeff H.]

Re: 1968 Vette Wiper Door Pops Up

Was told that the cannister or vacuum acutuator may not be the problem -- as it either works or not. And since my wiper door does goes up and down, it indicates there is vacuum action, thus it works. But I will check out the link you provided. Thank you Anthony!

[Terry M.]

Re: 1968 Vette Wiper Door Pops Up

When troubleshooting the C3 vacuum system it is important to understand the functioning if the system.

There are two parts to the system: CONTROL & POWER

The CONTROL system is the smaller hoses and the upper part of the diaphragm of the control relays.

The POWER system is the larger hoses the lower part of the control relays and the actuators for the headlights and the wipers.

The vacuum storage canister is part of both systems.

The CONTROL system has less volume than the POWER system and thus when the engine begins to provide vacuum to the entire system it will evacuate the control system first and the control system holds the parts (headlights and wiper door) in their last position as the POWER system begins to evacuate.

If your headlamps wink or the wiper door raises and closes their is a leak in the control system, generally the part of the control system that operates those parts.

Hunting vacuum leaks can be problematic because vacuum is invisible and usually almost soundless. I know that last sentence is stating the obvious, but it can't be overstated. I have had a lot of success with a electric vacuum pump (the kind used for air conditioning systems) placed outside the almost closed garage door with a long hose to the vacuum fitting at the intake manifold. A pair of long-nosed vice grips can pinch off different parts of the system as a means of troubleshooting. Don't forget the controls under the steering column. A leak there can effect the operation for the respective item that is controlled. I know those kinds of vacuum pumps are not inexpensive, but so is replacing parts until the problem is solved. Don't forget loose hose connections also.

Sometimes it can be as simple (easy to say) as the first fitting after the white filter, where the POWER and CONTROL system separate. That fitting is a check valve and when it fails the CONTROL system will leak down first. Remember it has the smallest volume.

[Curt S.]

Re: 1968 Vette Wiper Door Pops Up

I had a similar problem on my 69 coupe . I purchased a hand vacuum pump and began isolating the various parts of the system. My problem turned out to be a leaking at the seam vacuum tank underneath the front left fender next to the master cylinder. After removal , I took my tank to a gas tank repair shop and they repaired and coated the inside. It has been working flawlessly since. The vacuum pump was an excellent tool to check many parts of the system. If your car has power brakes, the removal is more of a challenge. Good Luck hope this helps. Curt

[Paul O.]

Re: 1968 Vette Wiper Door Pops Up

Jeff

When was your car built.

[Jeff H.]

Re: 1968 Vette Wiper Door Pops Up

Hi Paul,

Based on the VIN#, my car was built in March 1968.

[Jeff H.]

Re: 1968 Vette Wiper Door Pops Up

Hi Terry,

I will download your comments and share with my mechanic.

Thank you for your technical expertise.

Jeff

[Jeff H.]

Re: 1968 Vette Wiper Door Pops Up

Hi Curt,

I will take your information along with comments from others into consideration and have these possible causes checked out.

Thank you for sharing your technical expertise.

Jeff

[Don W.]

Re: 1968 Vette Wiper Door Pops Up

Dr Rebuild has a vacuum diagnostics plan and large color schematic of the vacuum system for purchase. See it here: http://www.docrebuild.com/dr-r-web/A-DROOP.HTML

[Jeff H.]

Re: 1968 Vette Wiper Door Pops Up

Hi Don,

I checked out the link you provided. Given the age of the vehicle, I may consider replacing the hoses as $80 is peanuts compared to what i've already put into restoration, notwithstanding a custom paint job that is upcoming.

Thank you for your recommendation!

Jeff

[Don W.]

Re: 1968 Vette Wiper Door Pops Up

Okay, you may want to take it to a shop that can do a smoke test where they pump into the system. There are hoses under the dash too. I found a cracked check valve via a smoke test that I would have never found otherwise. Good luck...Don

[Paul O.]

Re: 1968 Vette Wiper Door Pops Up

Jeff

Just to make sure you are having movement on just the wiper door? Not the headlight buckets. It is occurring while you are driving not when you are just starting the engine or after shut down . Are the hoses original? The headlights actuators the forward tubes do both pointing to the drivers side of the car? The reason for all the questions is there are hose differences from earlier 68's till approx Feb to Mar builds then later production cars. That could have an affect of it operation while just driving around.

[Jeff H.]

Re: 1968 Vette Wiper Door Pops Up

Will also consider that too.

Thank you!

[Jeff H.]

Re: 1968 Vette Wiper Door Pops Up

Paul,

The wiper door has popped open and closed while driving, not upon starting the engine or after shutdown. I have original hoses. I have to go to the shop to check how the headlight actuators are facing. What is the correct position -- opposite each other or...?

Jeff