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Thanks Joe, they close accordingly per your last post. Still no change, suspecting the switch still but happy to check other things.
That trapped energy just isn’t letting go when you move it back from COLD to HOT. You can feel the change in vacuum if you plug your finger over the black/white line, but on the car valve itself it just doesn’t release it.
Thanks Joe, they close accordingly per your last post. Still no change, suspecting the switch still but happy to check other things.
That trapped energy just isn’t letting go when you move it back from COLD to HOT. You can feel the change in vacuum if you plug your finger over the black/white line, but on the car valve itself it just doesn’t release it.
Can you post photos of both the Valve & your Switch.
If you have a model number or a link of the inline valve that might be helpful...
Something is ascue here...lol
Here's a thought. On your HVAC vacuum control switch. Under the console. It has 6 ports. 5 have vacuum lines going to it. One is left open to vent. Could that vent port be plugged?
Here's a thought. On your HVAC vacuum control switch. Under the console. It has 6 ports. 5 have vacuum lines going to it. One is left open to vent. Could that vent port be plugged?
Yes port 2 of the function control vacuum switch needs to remain open, but the HWSV and HWVS are not controlled by any of those ports on a A/C (or once) A/C car.
Now, if the car was originally a Non-A/C car port 1 would control the HWSV by the function control vacuum switch port 1 and port 5 would remain open (exhaust).
Yes port 2 of the function control vacuum switch needs to remain open, but the HWSV and HWVS are not controlled by any of those ports on a A/C (or once) A/C car.
Now, if the car was originally a Non-A/C car port 1 would control the HWSV by the function control vacuum switch port 1 and port 5 would remain open (exhaust).
I do know that currently, 2 is capped off. I’ve seen in other forums where the conclusion was to cap it off. So does 2 need to be capped? Sorry, I will get some pictures this afternoon when I have time to revisit it. I’ll uncap the 2 port if I need to. And it was AC equipped. Will be again eventually, so I have the lines set up as if it still was.
UPDATE
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Pictured below are the switch that I have (black/white vacuum - MIDDLE PORT), (black vacuum source line - REAR PORT), (front - Exhaust/Empty).
I have called CorvetteCentral on this piece that I ordered from them. They told me to see if the ports were backwards. I swapped the lines and it was just the reverse, COLD was depressed & HOT was pressed, but still no change in the valve once the vacuum was pulled - will not release energy.
Also pictured is the plastic/GM replacement valve that I got from NAPA. I have three of these things, all of them work. I should probably get the metal one that it was designed for, but that’s neither here nor there at this moment.
I took pictures of the one I’m using to test the vacuum switch. Pictures show plunger in what should be open, and then it’s position once it is stuck/wont release.
Yes, remove the cap from #2 port. The other actuators related to the heater/defrost and A/C "do" need to exhaust to change state.
If the plastic valve is not fully retracting after releasing vacuum (opening flow to heater core) it is defective.
Don't waste your time on the metal valves you can get form corvette vendors, they are all junk!
Just an example.... Here is a e-bay link for a USA made Ranco H25-144: https://www.ebay.com/itm/25480612842...3ABFBM-u3ehaNj
You can also use the Ranco H25-177, the only difference is direction of the vacuum port on the valve. It works just fine.
Here is a spare 177 I have.
Thanks! I’ll look into the valve more than likely, but what I’m saying is that the valve does release vacuum off the car. With a vacuum gun I apply 15 inches and it closes. Removing it, the plunger opens. When plugged back into the car, this is not the case. Which makes me think it’s that switch.
Conversely, testing the switch with the engine on, black/white line hooked up to vacuum gun… COLD pulls 15, and HOT drops to 0. So it may possibly not be the switch. It’s either one or the other…
and then one more question, in this forum you say that the 2 port should be capped towards the bottom of the thread… can you confirm which one is true? Not second guessing you, I’m appreciating this help! I just want to make sure.
Pictured below are the switch that I have (black/white vacuum - MIDDLE PORT), (black vacuum source line - REAR PORT), (front - Exhaust/Empty).
I have called CorvetteCentral on this piece that I ordered from them. They told me to see if the ports were backwards. I swapped the lines and it was just the reverse, COLD was depressed & HOT was pressed, but still no change in the valve once the vacuum was pulled - will not release energy.
I've been following this thread with some interest. The reason is I'm the manufacturer of the vacuum switch (the good one) that attaches to the heater box. This is the same switch as the wiper arm safety valve used in the '69 thru '72 cars to switch vacuum to the wiper door relay. This valve is not designed to release the vacuum signal when the plunger is depressed. The open vent port nearest to the plunger does nothing but vent to balance the pressure inside the dust boot if so installed like the original or import replacements. The vacuum must be vented to atmosphere somewhere in the vacuum circuit. I would also agree to open the capped vent port to allow the proper operation.
This valve is not designed to release the vacuum signal when the plunger is depressed. The open vent port nearest to the plunger does nothing but vent to balance the pressure inside the dust boot if so installed like the original or import replacements. The vacuum must be vented to atmosphere somewhere in the vacuum circuit. I would also agree to open the capped vent port to allow the proper operation.
this is what corvettecentral told me as well, but that it was the appropriate piece to order. Wonder if it’s just wrong in its entirety and I need to order a different one?
Thanks! I’ll look into the valve more than likely, but what I’m saying is that the valve does release vacuum off the car. With a vacuum gun I apply 15 inches and it closes. Removing it, the plunger opens. When plugged back into the car, this is not the case. Which makes me think it’s that switch.
Conversely, testing the switch with the engine on, black/white line hooked up to vacuum gun… COLD pulls 15, and HOT drops to 0. So it may possibly not be the switch. It’s either one or the other…
and then one more question, in this forum you say that the 2 port should be capped towards the bottom of the thread… can you confirm which one is true? Not second guessing you, I’m appreciating this help! I just want to make sure.
I confess I was wrong with my statement to you, #2 port should be blocked.
The function control vacuum switch exhausts out the switch itself, but only after the function control lever is moved passing by port 2.
Remove the vacuum hose from the vacuum switch going to the inline valve.
Connect you vacuum gauge to that port. Cycle the vacuum switch, vacuum at gauge when plunger is pressed in and when released gauge should drop to "0"
When pressed, the white/black line pulls 15 on the vacuum gun (engine on), and doesn’t immediately drop to 0 when released, but slowly makes its way there eventually when on depressed.
When attached, setting it to COLD sucks the plunger up inside of the valve but fails to release it when on HOT.
On the bench, the valve shows no issue, plunger goes up and down when vacuum is applied/released. Weird issue overall… I called corvettecentral again, they stated that what this forum has said: that the vacuum switch does not vent vacuum
My question however, is why advertise it as a 77-79 switch that requires that release of vacuum if in fact it does not do so in use?
When pressed, the white/black line pulls 15 on the vacuum gun (engine on), and doesn’t immediately drop to 0 when released, but slowly makes its way there eventually when on depressed.
When attached, setting it to COLD sucks the plunger up inside of the valve but fails to release it when on HOT.
On the bench, the valve shows no issue, plunger goes up and down when vacuum is applied/released. Weird issue overall… I called corvettecentral again, they stated that what this forum has said: that the vacuum switch does not vent vacuum
My question however, is why advertise it as a 77-79 switch that requires that release of vacuum if in fact it does not do so in use?
So we are in the same page...
We are talking about the Vacuum Switch on the heater box?
This switch has NO relationship with the HVAC function control vacuum switch...
i understand that the relationship between the switch on the heater box and the valve are exclusive, contingent upon the source line (black) switching over to the white/black line.
no issues anywhere else at this moment. I’ve double checked all other connections just to be sure.
i understand that the relationship between the switch on the heater box and the valve are exclusive, contingent upon the source line (black) switching over to the white/black line.
no issues anywhere else at this moment. I’ve double checked all other connections just to be sure.
If that switch doesn't exhaust, it is faulty...Period
Pull the blk/WHT hose, just a small shot in the port.
Then cycle switch manually. Then reattach hose.
If your looking to just return the switch for a refund or replacement just pull it. Don't do the WD thing.
They may not except it smelling like WD.
Haven’t quite decided, CorvetteCentral says that according to what I’m saying it’s not faulty. I pulled it and brought it inside to try to simulate what I’m seeing on the car.
Haven’t quite decided, CorvetteCentral says that according to what I’m saying it’s not faulty. I pulled it and brought it inside to try to simulate what I’m seeing on the car.
Thanks for the video!
Try connecting the vacuum pump hose to the red port and see if that changes things.
That switch is acting just like the switch I purchased MANY years ago with the stronger spring.
01-16-2024, 10:35 AM
