Q about heater core shut off valve.

[SS_Sean]

Hey, guys. My heater has been running constantly for a while... I found the vacuum line hooked up to the shut off valve was disconnected, and the heater was on constantly because of it. This is the little plastic inline valve which is over at the rear, and just above, the passenger valve cover, and is is inline with the heater hose.

My question is...is the valve closed with vacuum applied or not applied? At this point I'm not getting any vacuum signal through the line. The vacuum line runs along the top of the air conditioning box and dives down into the hole on the very rear corner of the fender, between the fender and the back of the a/c box. Where does this line go to, and how do I get a vacuum signal out of it?

Right now my air conditioning should be booming, but it's not. I suspect I still have heated water going through the core, and the a/c air is being warmed because the valve is not shut off.

Any help is greatly appreciated.

 

[SS_Sean]

ttt

 

[mikestertwo]

You need vacuum to close the valve.

 

[SS_Sean]

Thanks. Do you know where the vacuum line comes from? What's the source of the vacuum for the shutoff valve?

 

[mikestertwo]

The vacuum source is the hard line that feeds the EGR, cruise control, and AC/heater control on the left side of the motor. The line that goes towards the AC box is the one that feeds your AC/heater control. The vacuum line goes directly to your heater control on your dash. Your heater control on the dash will turn the vacuum on and off to your hot water valve.

 

[SS_Sean]

And where is this heater control located at? Are you talking about my controls on the dash console? I have that digital deal, so all it has hooked up to it is three electric plugs, no vacuum. Is this some sort of vacuum block under the dash? And if so, where's it located at? I've got to figure out why I don't have a vacuum signal on that line. Thanks for your help.

Ha...just noticed you're from Oregon, as well. No idea where warren is, though.

 

[mikestertwo]

Sorry to hear you have the digital control. Those things are very problematic. That's probably why it was never offered in 87'. I think there is a solenoid box that plugs into your digital controller. I think it's located just to the left of your glove box. If you drop the glove box you should be able to see it. I just parted out a car with the digital dash and can't quite remember where it was.

ps. Warren is just north west of Portland.

Ed

 

[salvageV6]

The vacuum solenoid programmer behind the glove box door should have a bunch of vacuum hoses going out of it.

The white hose or barb which turns into a grey hose near the unit is the one that runs the heater water valve.

Obviously test for vacuum on it with the car running and A/C on.

Violet hose is the inlet vacuum from your vacuum tank under the front drivers fender.

Make sure you have vacuum there first.

 

[SS_Sean]

You guys are the best! I'll check it out this week. Thanks!

 

[SS_Sean]

I don't have any vacuum to the block behind the glove box. It sounds like the supply comes from a tank behind the drivers fender, but where does this supply line run from-to?

 

[SS_Sean]

ttt

 

[aminga]

Courtesy of gnttype.org

 

[SS_Sean]

Thanks for that picture...that helps. What I'm specifically looking for is where the vacuum comes from to hook to this 'tank' behind the driver's fender, and where the vacuum line passes through the firewall from the vacuum tank to the block behind the glove box. I have no vacuum at the block and now need to start back-tracking to find where the break or pinch in the line is. Thanks for the help!!!

 

[SS_Sean]

ttt

 

[IrvJr]

Thanks. This thread helped me too. What happens if the vauum control mod is unplugged? Would that stop me from getting vacuum to my controls. I was not getting hot air when the heat was on, but if i manually opened the valve it would blow warm air. Does the valve open when you apply vacuum or prevent? Could my valve be on its way out? Is it ok to a ask a question or 2? haha.

Thanks

 

[mikestertwo]

Does the valve open when you apply vacuum or prevent?
Thanks

The valve closes when you apply vacuum.

 

[salvageV6]

Mike is correct the valve closes when you apply vacuum.

However when the vacuum disappears the valve may remain shut if the spring doesn't pop the thing open and move the arm.

Check for proper operation visually on it and move the arm manually if it won't budge or hasn't been open in a while.

Make sure the pipe into the heater core and the pipe out of the heater core are at the same temp. when it's open.

 

[IrvJr]

That doesnt make sense for my prob. So if the valve is closed am i to assume that the coolant doesnt flow? So no vacuum means hot air all the time? I have no hot air unless i manually open the valve. Anyways i found my control unit unplugged, lets see what happens tomorrow.

 

[salvageV6]

If your spring is shot or weak or the valve corroded at the pivot point it won't open with or without vacuum present.

Apply vacuum to it and note how much force it takes to try to open it, then when vacuum isn't present check the force necessary to open it, if it doesn't open on it's own that is, it should be minimal.

Those things need a bit of lube to work okay and depending if they have been moved a bit from vertical they don't always work with the spring especially if it's 20 years old. I've got one on my car that's aftermarket plastic that works better than the metal ones.

I'd bypass the thing for winter with some hose, then, out of the car, you can make sure it functions smoothly indoors and can get it cleaned up.

Just run a long vacuum hose from the car into the warm house if you're up here in the North, too cold to work on that thing today.

 

[IrvJr]

Well it did take a bit of force to open it by hand. It is a metal one that has been there since i got the car in 2000. Maybe it needs replacement. I will make sure there is vacuum present. Thanks for the help.