Alan

Doc - No! - I think you need to re-read it...

Who mentioned vacuum lines, valve changes? - this could be done without even removing the water valve

The actuator is controlled in exactly the same way as now - no vacuum lines get changed at all.

The water valve is now open with vacuum and closed without - thats all that changed there.

A relay is added to reverse the sense of the control signal to the vacuum solenoid

The system works exactly the same as stock - except the water valve stays closed when parked

In contrast:

A choke control snaked through the firewall & dangling in the glovebox is the real rube... no?

Alan

rssmith

Finally a topic that I have additional information on that is still pertenant.

I replaced our water valve with a NAPA part and added the relay. The pluses are teh NAPA part was about $20, it opens with valcuum instead of closing, and it has a compliant valve face for a positive seal. If you look at our valves it has a plastic gate sliding over the hole in the body and is never really water tight, especially after a little time in the 200 degree water bath. I see I have lost the part number, sorry, I had found it by thumbing through a catalog they had with dimensions and the normally open or normally closed sense listed.

Alan

Even better - will you be able to find the part number...?

Anyone else do this - I like this idea a lot also - our valves do look a little flimsy to me...

Is it one of these?:


http://www.napaonline.com/NOLPPSE/(S...805_0228876897

http://www.nostalgicairparts.com/air...-valve-514.php

Alan

PS Roger - isnt this our stock heater valve in generic disguise:


http://www.napaonline.com/NOLPPSE/(S...09A_0230118096

borland

Alan,

I figured this out long ago, its amazingly simple, just never found a good price on a used 928 Climate Control solenoid valve to make the install. So simple, I get a good laugh when I see other solutions implemented.

All you need is one extra 928 HVAC solenoid valve, slightly modified, and added inline with the heater valve vacuum actuator, and connected to the ignition switch so that it is activated when the ignition switch is On. When the ignition is cut, the vacuum actuator to the heater valve can't release vacuum leaving the heater valve shut (that assumes the heater valve is already shut, which would normally be the case in summer weather).

The stock solenoid at first glance appears to be a two way valve, but is actually a Three-way valve. One port looks blocked, but it is actually an air bleed, so that when power is cut to the coil, the solenoid valve shuts from the vacuum source and air is then allowed in through the other port to feed atmospheric pressure (air) into the vacuum line, thus releasing the vacuum actuator which allow the heater valve to open.

So for this additional solenoid valve, the modification is to block the vent port with a cap or other method. Since power to the additional solenoid valve would be ignition controlled, the HVAC can operate in its usual manner.

docmirror

Ok, so now you want to change the water valve too. I get it. in your OP you wanted to hold the water valve closed with vac when it was off, which is a hassle. If you change the water valve to normally closed, then use the relay you don't need any new vac lines, just the valve replaced and the relay to swap the actuation of the signal to the solenoid. Better plan. I still think the choke cable to keep it off when not needed is darn easy. It's the way car HVAC was done up till the 70s and is darn reliable.

Alan

Doc - WTF is going on with you...? I never said half of what you attribute ... ?

I said that from the beginning. To me modifying the exisiting valve to work as normally closed or switching to an alternate normally closed valve achieves the same thing... whichever is easiest...

I never said that... where did it come from? as far as I can see Borland just proposed it now...

This was the proposal all along... who said anything about additional vac lines - only you I think...?

Maybe reliable - but its clearly a kludge and breaks the functionality of the temperature control - why do that?

You seem to think I have been saying lots of things I never said... I don't get it?

Alan

wcj928

Can you post the actual NAPA part numbers as the links do not work? Thanks.

Alan

Walter - yes the links are a pain - they worked initially (for me only I'm sure) but the NAPA site is a pain in the *** to navigate. Hard links seem to be impossible - they are dynamic.

Its an Altrom part # 1572805 or ATM 1572805

Search for part number atm1572805

Note I havent tried this yet - looks like it has the same approx dimensions and pipe/flange sizes. be nice if rssmith can confirm this is the one he successfully fitted...

Alan

dprantl

Alan, I didn't like the look of those heater valves. They had metal vacuum actuators, but the part where the coolant flows was still the same plastic (i.e. still looked flimsy to me). I installed this one into my wife's 968:

http://www.napaonline.com/NOLPPSE/(S...410_0229610010

It's been working fine for a couple of years now. I am thinking of putting the same one into my GT. This valve I think is the same functionality as stock though.

Dan
'91 928GT S/C 475hp/460lb.ft

Alan

I agree this one is still half plastic - it does look slightly more robust - but thats probably just a subjective thing - absent any real data. However all these are designed for basically the same job...

Although I've heard many tales about major coolant loss at this point it always seems to be the pipe splitting or coming off the valve - not the valve itself self-destructing - so maybe even the stock valves are OK.

I do more frequently hear of poor sealing/leaking past the valve - so maybe thats the bigger potential issue. I don't know how you'd rate designs comparatively without a lot more data.

At <$30 its probably easy to justify just buying 2 of them...

Alan

docmirror

Aycarumba. I don't see anything in the OP about changing the water valve, just the sense mechanism to hold it closed. If you could please point me to where you advise changing the water valve in the OP?

<edit; nevermind, it's just not that important.>

Alan

Borland - interesting idea...

The early <'84 vacuum solenoid valve banks had 6 solenoid valves not 5 like the later versions - easy to adapt that version to this idea. Though you'd also need to modify the manifold to truncate before the last valve.

I do think this has some merits functionally because you'd probably maintain more heat in the heater in the winter too.

But I'd be worried that the vacuum would leak down too fast... anyone know how good these solenoid valves are - in normal operation a tiny bit of leakage wouldn't really matter (in vent or vac mode) - in this case it really would...

Also how well can can the vent be plugged - is it in fact a regular vacuum port on the valve

This method does also have the benefit of better system water circulation and air purging when refilling the coolant system with the car off (if you were last in heat mode) - default valve closed behaviour is not as good for this (you'd have to be running...!)

Alan

Alan

Doc, I quite agree...

I have no idea what crusade you are on... I think I have been quite clear and consistent from the beginning in what I want to do - including why. (Hint - the 'water valve' is both the flow valve & the vacuum actuator - thats how they come)

If you see it differently fine - I don't see any point in responding anymore... just put your cable choke control in and enjoy.

Alan

ZEUS+

Why not install a normally closed water valve ahead of the factory one. Link from post 18.
http://www.nostalgicairparts.com/air...-valve-514.php
Have the vacuum supply come from the same source as hvac, so rpm wont affect vacuum signal. Edit:Install a vacuum solenoid inline to water valve. Power solenoid with ign on. Ign off vacuum bleeds and valve closes.

Alan

I don't think there is room for 2, and in any case I'd rather have fewer valves.

Your solution is more complex... 1 relay & 1 normally closed valve - this gets exact stock running behaviour and normally closed engine off behaviour. No power is consumed when off...

Alan