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Can and does the wiper door solenoid on the tach typically fail open or closed.
My wiper door was working but has not been operated in about 2 years.
The door does not work with the override or wiper switch. If I push it open manually it will close but slowly with override pushed in.
I compared the vacuum on the blue hose for the headlight door override to the blue hose vacuum on the wiper door. The headlight door has a really good vacuum while the wiper door is very weak.
My understanding is the blue striped hose has vacuum all the time until the wiper door solenoid is activated.
If that is the case could that solenoid fail partially closed or open?
I also know that I have plenty of vacuum at the canister since I opened it manually and it has really good vacuum. When I put my hand over the hole with the rubber plug wiper door closes exactly how is should.
I am asking all this because getting to that solenoid is not easy. The good news is I have an NOS solenoid if needed.
You can rest easy, it is not necessary to remove the solenoid to test it's function. The default position of the solenoid is for vacuum to pass through it, allowing vacuum from the "T" to reach the override switch. The default position of the override is when pushed in it will allow vacuum to pass through it to the middle port on the wiper arm safety valve located under the passenger side wiper arm. Therefore it is possible to use the vacuum signal at the safety valve to test if vacuum is reaching it when the solenoid is off or energized. Simply connect a vacuum gauge to the hose on the middle port of the safety valve, and observe the readings with the car running and wiper switch off and then on.
If you have no vacuum reading with either the solenoid off or energized, I can direct you to the next series of tests.
You can rest easy, it is not necessary to remove the solenoid to test it's function. The default position of the solenoid is for vacuum to pass through it, allowing vacuum from the "T" to reach the override switch. The default position of the override is when pushed in it will allow vacuum to pass through it to the middle port on the wiper arm safety valve located under the passenger side wiper arm. Therefore it is possible to use the vacuum signal at the safety valve to test if vacuum is reaching it when the solenoid is off or energized. Simply connect a vacuum gauge to the hose on the middle port of the safety valve, and observe the readings with the car running and wiper switch off and then on.
If you have no vacuum reading with either the solenoid off or energized, I can direct you to the next series of tests.
Dave
It seems the vacuum is not passing through except a a very very low level when either off or energized.
I am starting to think that when I pulled the steering column I may have pulled the vacuum line off the headlight switch. The part that is confusing me is I have a very low level of vacuum on the blue striped hose at the override switch regardless of the state of the solenoid. There is a strong vacuum on the blue striped hose for the headlights. Headlight doors work perfectly.
When looking at the Dr Rebuild diagram I used originally it looks like the source vacuum for the headlights is the same as for the wiper door that attaches to the headlight switch. There is a tee that has a white striped hose that goes to the headlight switch and a yellow off the tee to the solenoid.
Am I correct in thinking that the side of the tee that goes to the headlight switch must be connected since the headlights work perfectly and the headlight override works perfectly.
I guess we are back to the solenoid behind the tach.
Something I see a lot of may also be your issue. The port on the solenoid that is connected to the override is tapered. This would make a very loose connection if the original vacuum hose is still in place due to age. If you have a very loose connection there, snip off a little of the hose and reconnect it. Here's a pic
Another good test would be to use your new solenoid in place of the old one. Leave the old one there, just connect the power and the 2 vacuum hoses.
Keep in mind that it does not work with the override switch either.
I am beyond frustrated. The vacuum should just pass through the solenoid to the bypass switch via the blue striped hose. The headlight side of the same vacuum line from the source has great vacuum at the override switch. The wiper door side of the override switch has almost no vacuum.
I have confirmed that the yellow line to the solenoid has excellent vacuum.
Looking more and more like the solenoid is blocking all vacuum to the wiper door in either mode.
What I don't understand is that I thought no vacuum would allow the wiper door to open.
If I reverse vacuum lines at the canister should the wiper door open?
Just a quick update. The wiper door actuator seal had somehow come out. Fixed that and now the door works as it should but won't stay put with engine shut down.
Hi Bill,
The 'fail' condition for the system was designed to be 'open'. (For both the wiper door and headlight doors.)
So perhaps a slow leak?
Maybe test the check valve first?
Regards,
Alan
Hi Bill,
The 'fail' condition for the system was designed to be 'open'. (For both the wiper door and headlight doors.)
So perhaps a slow leak?
Maybe test the check valve first?
Regards,
Alan
Good suggestion. It is original and easy enough to check.
All worked perfectly before being unused for a couple years.
Hi Bill,
Did someone come to look at your car yesterday?
Regards,
Alan
Yes and the wiper door worked until I tried with him.
He loved the car but was concerned the engine had not been rebuilt and I lack some documentation. I cannot see a reason to rebuild a perfectly good engine that does not burn a drop of oil or tap. It idles perfectly and even goes through the warm up kick down sequence perfectly. I started it cold to demonstrate the kick down sequence.
I took him out for a nice ride and REALLY ran through the gears. Took her up to about 5500 RPMs. Car ran flawlessly. It rides like a brand new Corvette from back in the day and shifts perfectly.
Headlight doors opened slowly and I discovered a hose that was barely on so that problem is resolved. Now they open exactly as designed again.
Alarm works now I just need to button up the wiring for the sx hood switch. I found my original connector.
Funny how just sitting causes minor issues.
I really would love to see her judged before I let her go.
Hi Bill,
The 'fail' condition for the system was designed to be 'open'. (For both the wiper door and headlight doors.)
So perhaps a slow leak?
Maybe test the check valve first?
Regards,
Alan
Hi Alan,
Well the check valve is definitely bad. You can easily blow through any hole in either direction.
Wiper Door Solenoid
