WTB: FICD and Vacuum source magnet valves

[gwri8]

Hi Folks,

I've narrowed down my Heat/AC vacuum problems to the magnet valves on my 77'.   Anybody have a working set they want to sell or know where I could find them?

[siteunseen]

Have you seen this thread?  Might give you an idea 

 

[gwri8]

Thanks Cliff, and yes, I have been through that thread and everything else under the dash for the last 3 days.  Vacuum is good from the manifold

 to the reservoir tank and lost just after the vacuum source valve. All the other actuators and lines check out

[Captain Obvious]

Not saying the valves are OK, but just because the vacuum isn't getting through them, doesn't necessarily mean the valve itself is the problem. There are lots of other electrical things that could go wrong that would make the valves not operate when they are supposed to.

Hoping I'm not telling you stuff you already knew, I whipped up this little snippet from the wiring diagram:

[gwri8]

Thanks CO.  No doubt about it that Mr. Electricity and I do not get along very well ever since that (those) time (times) he bit me so any furtherance of my education(or lack thereof) is appreciated.  I'm not too concerned with the AC part just now (season change and all). Just for starters, I know it needs a compressor (locked up), a pressure switch (wires broken) and of course the unicorn drier for a 77'.  I do want to try to keep it as original as I can.

But all that aside, the heat should work and there's no heat at the moment via the dash selector/vacuum. No "thunk" from the mode door when engaging the levers.  There are no leaks at the heater valve and hot water travels to the heater core.  It did have intermittent heat last winter, but would heat for maybe 30 minutes or less and then stop.  

Since it was a mild winter last year it wasn't so much of a problem, but I'm on it this year.   I've checked continuity and ran 12v to each of the magnet valves seperatly and they "clicked" when they should have as well as confirmed power to them. As far as my limited electrical knowledge goes, I know that does not necessarily mean they are good.  Is there a better way to confirm their function?  

[Captain Obvious]

The magnet valves are just an electrically opened valve. With no power on them, they are closed, and with 12V on them, they should open. You should not be able to blow air through them with no power to them, and if you put power on them (and they click), you should be able to blow through them.

Other thoughts? The magnet valve on the left (in the wiring diagram) only actuates when the compressor runs and it supplies vacuum to the FICD. So that one will never actuate if the wires are broken to the pressure switch. But that one has no effect on anything other than the FICD, so it shouldn't be affecting heat at all.

The magnet valve on the right is the one that controls everything else, and it should be opening any time the key is in ACC or ON, and the fan is running.

I'm not sure why they bothered to tie it into the ignition though. I'm guessing they didn't want you to drain all the vacuum out of the reservoir bottle while you were sitting with the engine off. Playing with the mode lever... Moving it around a bunch of times just to listen to the flapper doors move, until you had drained the vacuum bottle? Anyway, with that theory in mind, they cut off the vacuum to the system when the ignition is off.

So, to test the rest of the heater system, you could completely bypass that magnet valve. Just jumper the vacuum tubing around it to test the rest of the system. You will be putting vacuum on the rest of the system all the time so you will probably drain your vacuum bottle overnight. But to test the heater, it should be fine.

As a side note that might not really matter right now, but... There are two sections to the fan switch. One section is the 1 through 4 speed controls, and the other is an "fan is running" output. That "fan is running" output gets tied to ground whenever the lever is set to anything other than OFF and the "fan is running". The insides of my fan switch were green, crusty, and intermittent, and I'm wondering if maybe yours is as well. I took mine apart and cleaned it all up nice and put it back together. Works great now.

I got pics if you're interested.

[Patcon]

Photobucket sucks!!!

Just thought I would add that here... squirrel!!!!

[Captain Obvious]

I know, right?

And just because I can post pictures WITHOUT photosuckit, here are some pics of the fan control switch. Might not even be the problem, but just because I can.

Fan switch:

Unbend the tabs to open up the switch. Green crusty grease and corroded copper contacts inside. The four nibs along the top are the four fan speeds. The solid bar (the OFF bar) at the bottom is the "switch is NOT in the OFF position".  (for my nerd friends... Get it? "OFF bar").     Anyway:

Cleaned up all the contacts with some scotch-brite or 800 grit sandpaper. I put some grease on after the pic:

Rebend the tabs back over to hold the switch back together and you're done. What was intermittent, now works perfect:

[Captain Obvious]

Oh, and all this talk about the magnet valves and vacuum tubing makes me sooooooooo, soooooooo glad that I changed over to the electric servo control for the HVAC system!

So glad! 

[gwri8]

17 hours ago, Captain Obvious said:

Playing with the mode lever... Moving it around a bunch of times just to listen to the flapper doors move, until you had drained the vacuum bottle? 

 

Waaaayyy too many opportunites to segue straight to the gutter here and since I don't need much of a lead...  I shall refrain.....  and just to be clear, I'm not a prolific lever flipper.  It either works or it dosen't in my general operating procedure.

17 hours ago, Captain Obvious said:

So, to test the rest of the heater system, you could completely bypass that magnet valve. Just jumper the vacuum tubing around it to test the rest of the system. You will be putting vacuum on the rest of the system all the time so you will probably drain your vacuum bottle overnight. But to test the heater, it should be fine.

 

I followed your advice here and after I moved the vacuum source tube around I finally bypassed everything,  Mag valve bracket and the vacuum bottle. It turns out that the check valve was bad.  Apparently it was leaking slowly and wouldn't hold any pressure.  I've never heard of one of those to go bad before, but I learn something new everyday.   Fortunately I have a whole bracket from a parts car.  The mag valves were toast on that one but I never throw anything away and still had it in my stash!  I was able to use the check valve from that one with success.  Now there is glorious heat on demand!  A whole new season of driving is now an option.  So Thanks Cap'n!

[Captain Obvious]

So all this talk about electrical problems and wiring diagrams and switch rebuilding... The problem was the check valve between the manifold and the vacuum bottle?? That's awesome!! Glad it was that easy!! (And cheap!) Awesome!

I can picture you in your car in the garage tonight, moving your lever back and forth. Back and forth. Back and forth.

Go ahead...  

[gwri8]

1 hour ago, Captain Obvious said:

So all this talk about electrical problems and wiring diagrams and switch rebuilding... The problem was the check valve between the manifold and the vacuum bottle?? That's awesome!! Glad it was that easy!! (And cheap!) Awesome!

I can picture you in your car in the garage tonight, moving your lever back and forth. Back and forth. Back and forth.

Go ahead...  

I think I'm getting so good at it I can switch hands and gain a stroke.... no pictures allowed