HVAC solenoids
08-04-2016, 07:31 PM
#1
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Thread Starter
HVAC solenoids
I tested them and four of them seem perfect. One of them seems slightly less than perfect, but I don't know if it's enough to matter.
My testing method was as follows:
- Connect vacuum pump to solenoid vacuum input
- Test vacuum (should hold)
- Apply power to solenoid, test vacuum (should not hold)
- Cap vacuum output, power still applied, test vacuum (should hold)
For the one failure case, it very slowly lost vacuum in the last test case. I didn't time it all the way down, but I would guess it would take about 30 seconds to lose it.
This solenoid is the fourth one from left, sitting in the driver's seat, so I think that's the heater valve. Which is important, because I'm going to want that sucker closed almost all of the time here in Florida, which means vacuum applied. Of course, it's not just three pumps on a hand pump in the car, it's a constant vacuum source, more or less, so this is slow enough it might never be apparent.
Counterpoint: The whole freakin' dash is in pieces, so if I'm ever going to do it, now would be the time...
My testing method was as follows:
- Connect vacuum pump to solenoid vacuum input
- Test vacuum (should hold)
- Apply power to solenoid, test vacuum (should not hold)
- Cap vacuum output, power still applied, test vacuum (should hold)
For the one failure case, it very slowly lost vacuum in the last test case. I didn't time it all the way down, but I would guess it would take about 30 seconds to lose it.
This solenoid is the fourth one from left, sitting in the driver's seat, so I think that's the heater valve. Which is important, because I'm going to want that sucker closed almost all of the time here in Florida, which means vacuum applied. Of course, it's not just three pumps on a hand pump in the car, it's a constant vacuum source, more or less, so this is slow enough it might never be apparent.
Counterpoint: The whole freakin' dash is in pieces, so if I'm ever going to do it, now would be the time...
08-04-2016, 10:22 PM
#2
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I have just been going through this as well. My thought is like yours. It probably won't be a problem as it is, but since everything is apart I would replace it. It probably isn't going to get better, only worse.
Best of luck.
Best of luck.
08-05-2016, 01:30 AM
#3
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Thread Starter
Yeah, seems like sound advice. I've got an email in to 928 International to see what a used one will run me.
08-05-2016, 04:54 AM
#4
Rennlist Member
Jeff,
Your test method is logical. I would replace any solenoid that cannot hold vacuum- if it is truly leaking it is not going to get any better and can [easily?] get much worse.
Just try to ensure that the leak is coming from the body and not the test cap you are using. Perhaps you can try a pneumatic pressure test at a low pressure [10 psig?] to see if you can see where the leak may be emanating from and even then it is not a "bullet proof" test but probably better than nothing.
Rgds
Fred
Your test method is logical. I would replace any solenoid that cannot hold vacuum- if it is truly leaking it is not going to get any better and can [easily?] get much worse.
Just try to ensure that the leak is coming from the body and not the test cap you are using. Perhaps you can try a pneumatic pressure test at a low pressure [10 psig?] to see if you can see where the leak may be emanating from and even then it is not a "bullet proof" test but probably better than nothing.
Rgds
Fred
08-05-2016, 01:11 PM
#5
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Thread Starter
Honestly, I can't find my little box of caps and was using my finger...but I could consistently get all the other four to work fine.