mysixtynine

Guys

My vacuum tank immediately empties out when I shut off the car. So this leads to the infamous open and close of the wiper door at startup (because there is no vacuum left in the tank to keep the signal to the actuator relay in the UP or wiper door closed position). (my tank is good and holds vacuum if I block off the line to the tach solenoid.)

My headlights have been eliminated with the probe motors. So the headlight switch vacuum hose has been eliminated and goes directly to the tach solenoid only.

If the car is running and I use the wiper bypass switch (pull down) or the wipers electric switch the door opens as expected and closes as expected when I turn off the wipers or disable the bypass (push it up).

I have a hissing in the car when the engine is running. Coming from the wiper tach solenoid foam filter (new solenoid car did not have a wiper door when I got it). I figure this is normal since they have the little foam filter on it?

But that is where i am loosing my vacuum reserve from when the car is shut off. When I look at the diagram the metal nipple on the tach solenoid goes to the line that ultimately goes to the 2 nipple metal check valve which the other nipple (of the pair) goes to the vacuum tank.

So if my vacuum is bleeding off from the foam vent how am I supposed to keep vacuum in the tank?? Is my tach soleniod bad and NOT supposed to be venting the vacuum when NOT energized? I mean the only way I see this NOT venting is when its energized and the plunger is set to block the vacuum at the metal nipple?

At this point I dont understand the vent... or what its need for or maybe mine is not right... I dont have an orgininal and cant find anything to tell me what its for in other posts.

I just thought of something to try... Ill start the car and turn the wipers on... leave them on and shut off just the ignition and leave the wipers runnins which should leave the tach soleniod energized which should then stop the hissing from my foam filter... but if that works does it mean the soleniod is bad?

toobroketoretire

The headlight switch and the tach solenoid both have a vent for this reason: When vacuum is applied to a device the vacuum has to be relieved thru that foam vent when the device is shut off. If the vacuum couldn't be relieved the device would stay in operation continually.

The FRONT nipple of the headlight switch is supposed to be connected to intake manifold vacuum and if you have those two hoses switched vacuum will leak out of the foam vents continually.

7t2vette

Take a look at my wiper door vacuum to electric conversion thread in the general section....uses the same electric motor as the headlight conversion.

https://www.corvetteforum.com/forums...onversion.html

mysixtynine

Do you think the foam vent should leak vacuum? I get that it would be there to allow whatever you are actuating to go back to its normal non vacuum applied state.... but should it allow the vacuum tank to drain off?

mysixtynine

haha... i checked this out before ... pretty slick. My vacuum setup is real simple ... i just need to figure out why the soleniod is leaking the tank vacuum? If that stopped then it work fine as i would have vacuum present when starting so that the wiper door didnt cycle.

Dave J

Here's a couple of my diagrams showing the vacuum path at the 2 different scenarios, the solenoid not energized and then energized. Maybe this could help explain how the solenoid is supposed to work.





Port A - vacuum inlet
Port B - to safety valve under wiper arm
Port C - solenoid vent

With the solenoid not energized, vacuum is pulled through it to ultimately evacuate the control portion of the relay.
With the solenoid energized, vacuum escapes (allows atmosphere in) through the vent on the end of the solenoid, and is captured (blocked) at the inlet port.

mysixtynine

Hey I found this post... from the looks of it that spring should be making the solenoid needle seat go backup when NOT energized and block the vacuum from leaking out of the solenoid body......hmmmm

https://www.corvetteforum.com/forums...m-and-fix.html

Ill bet mine is simply leaking... dang thing is brand new... probably should not be hissing ever except for the short time it takes for the actuator relay to back to open state without vacuum applied!!!

mysixtynine

Awesome pics txs ... I found in my post just seconds after yours ... someone had taken a solenoid apart.

So should I assume that this solenoid should NOT be leaking vacuum on a regular basis just when it transitioning?? Because mine appears to be leaking and so its draining off the vacuum tank immediately. My guess is that little needle/spring is NOT blocking off the vacuum on the plastic port inside when its NOT energized.

Dave J

Several things come to mind here..........

First of all, what is actually happening when you hear vacuum leaking? Is the solenoid energized or not.

Normally, when the solenoid is energized, the atmosphere replaces the vacuum in the components and the hoses from the rear of the solenoid to the relay. It should sound like a HHhhiiiiiiissssssssssss for about a second or two. That's all. You should have full vacuum leading to the metal inlet port on the solenoid.

You can test the solenoid for proper operation with it in place simply by using short test hoses and a Mityvac, or even your lungs. Simply simulate the operation in the 2 diagrams.

Disconnect and mark the 2 vacuum hoses. Solenoid NOT energized, test the vacuum path through the metal port to the 90 degree plastic port. It should pass right through, and be blocked when the output port is blocked with your finger. Vent should be blocked.
Solenoid energized, vacuum will not pass through the metal port, and will pass through the straight (vent) and 90 degree plastic ports.

mysixtynine

I have hissing all the time no matter if its energized or not while engine is running.... so this is leading me to believe that internals are not right on my soleniod... its not a brief hisssss. Its all the time and thats what makes me think this is whats draining the tank off.

Dave J

One last thing before you pull the solenoid, make double sure you have the vacuum hoses connected right. Here's a diagram if you do not have a good one.

mysixtynine

Ok.. Tested the tach solenoid... It's fine. Txs for all the diagrams!!! Printed everyone for safe keeping. The hissing sound is due to vacuum running through the system from a leak elsewhere it just seemed to be from their since the vacuum flows through it. I traced the leak to my new wiper door actuator. If I remove the solenoid and apply vacuum to it its source hose It just leaks down. If I'm quick enough with my mighty vac pump the wiper door opens. So now I found hissing in the wiper door actuator... So if I pull the red hose off the actuator the hissing stops and the system hold vacuum. So my guess is the diaphragm in the actuator is bad... I should be able to apply vacuum to either side (green or red) of the actuator and it should hold vacuum right?

Dave J

Correct.

Sounds to me like you're on your way to a functional wiper door system. I do not use the color system of hoses, mainly because after so many years, these can and do get played with. If either the front or rear seal and/or port is leaking, there is a good possibility it could be repaired. The front can leak from the rubber plug. I always glue these in. The rear seal can be simply replaced.

What is the condition of your safety valve (under passenger wiper arm)?

mysixtynine

Dang it I'm getting tired of new bad parts.

The safety valve works so far .... That's was a new bad one from corvettecentral but they replaced it free.

I figured that the actuator should hold vacuum either side... If I don't put my finger over the other sides port the vacuum just falls off...if I put my finger Over it the system holds vacuum ... Of course the actuator will be bound because that side can't pull in atmosphere but it doesn't leak... Man this is pissing me off stupid bad new parts... Hard enough to understand this system but add bad new parts...I had to have the wiper door!!!

Dave J

Take a deep breath and relax my friend. This isn't hard at all, you're getting closer all the time.

If you have to block the opposing port to get the actuator to seal, the internal diaphragm must be torn. Once installed, one port or the other is vented to atmosphere through the relay. The actuator should hold vacuum simply by connecting to only one side.

If you have a new Chinese safety valve it is probably defective also. Lets get the actuator doing what it's supposed to be doing and we can attack the next component.

mysixtynine

I know... I appreciate all the help and all the docs.

The actuator isn't a cheap part.. And it was new. Have to see if the place I got it from will replace it but my guess is no got it several yrs ago but it's on a car that's goi g through a restore so it gets no use.