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1981 (c3) heater control valve, I’ll replace the original and saw that the valve was open (just like the new one I Purchased) My question is, does the vacuum from the control switch line close the valve constantly when the heater control switch in The car is off,,is vacuum, always keeping the valve closed ?, I am confused on how it’s supposed to operate properly. Will someone please be kind enough to tell me how the vacuum control valve is supposed to work?. I would appreciate it. Thank you for your time and consideration.
Larry
1981 (c3) heater control valve, I’ll replace the original and saw that the valve was open (just like the new one I Purchased) My question is, does the vacuum from the control switch line close the valve constantly when the heater control switch in The car is off,,is vacuum, always keeping the valve closed ?, I am confused on how it’s supposed to operate properly. Will someone please be kind enough to tell me how the vacuum control valve is supposed to work?. I would appreciate it. Thank you for your time and consideration.
Larry
The Hot - Cold slider lever is attached to a cable. The cable is connected to a lever arm that presses on a vacuum switch that sits on top of the heater box. When Cold is selected a vacuum signal is sent to the inline hot water shutoff valve. The vacuum switch also has an exhaust port so when you change from cold to hot the trapped energy (vacuum) can be exhausted so the inline valve can change state.
So yes, normal position holding the valve in your hand would be open.
Thank you, so if the valve does not close when I slide the lever control to off and I continue to get heat into car, where should I start to fix problem ? The heater box?, the slide control,
vacuum switch? I’m sorry but I was given this car as a gift from my son, and have been working on it for the past nine months and this is one issue I’d like to figure out.
thanks again for your time, sir
Thank you, so if the valve does not close when I slide the lever control to off and I continue to get heat into car, where should I start to fix problem ? The heater box?, the slide control,
vacuum switch? I’m sorry but I was given this car as a gift from my son, and have been working on it for the past nine months and this is one issue I’d like to figure out.
thanks again for your time, sir
The HOT - COLD slider lever has NO off position.
You must be talking about the upper function control lever.
Yes, I stand corrected. That’s what I was referring to,in any case. I just don’t know where to start to determine where my problem lies, in the control cable ,in the switch on the heater box, I guess another question is why wouldn’t I have any vacuum going to the heater valve
i’m sorry if I sound naïve, I did a lot of work to this vehicle I consider myself somewhat of a motorhead, but this is Greek to me
Again, thank you for your time
My next step would be, with the car running remove the vacuum line on the hot water shutoff valve, slider lever in the COLD position and see if you have a vacuum signal at the hose end.
With your finger tip or a vacuum gauge if you have one, then slide the lever to HOT and test line.
If No vacuum signal in the COLD position the cable or the switch on top of the heater box is not adjusted correctly or the vacuum switch is faulty.
This is the switch bmotojoe is referring to. It sits on the top of the heater box. The Hot/Cold lever has a wire connected to it. When in the COLD position, the metal lever needs to depress the plunger fully not just touch it. That plastic plunger sticking out opens vacuum to the heater valve in the engine compartment which then closes the valve. Mine wasn't depressing the plastic plunger fully either letting hot coolant constantly enter the cabin. Note that the cable also controls the hot/cold flapper door. In my case, it wasn't fully closing the flapper door letting hot air constantly flow into the cabin as well. If you trace that control cable back you'll find under the passenger console panel an adjusting mechanism that's plastic on the cable. That adjuster will allow you to lengthen or shorten the cable so you can adjust it to make sure it closes the flapper and plunger properly.
BTW, if you need to replace the heater valve in the engine compartment, I like this one. Works the same as the original but instead of just blocking the coolant flow, it recirculates it back into the block. A much better design in my opinion. Hope that helps!
Thank you, as I understand what you’re saying is that I should try to make an adjustment on the cable to see if I can remedy the problem before I look into replacing any parts and this adjustment will hopefully correct the situation especially the vacuum issue.
if not a new vacuum switch would be in order ?
thanks again I truly appreciate the information you have provided
Larry
Thank you, as I understand what you’re saying is that I should try to make an adjustment on the cable to see if I can remedy the problem before I look into replacing any parts and this adjustment will hopefully correct the situation especially the vacuum issue.
if not a new vacuum switch would be in order ?
thanks again I truly appreciate the information you have provided
Larry
Do the vacuum test at the Hot Water valve first (Engine running Slider lever in COLD position).
Yes sir, And there is no vacuum at the line that connects to the control valve when the heater control in the vehicle is in the cold position.
do you know the rotation of the adjustment that extends the cable rather than the retract it?
again, thank you very much for your time.
at the present time, I do not have the area opened up in order to make such adjustment but I’m just curious to know which way to turn the adjust
Well it sounds like the heater valve is not closing since your asking the question on here but as bmotojoe mentioned, testing for vacuum on the line going to the heater valve is easy and quick. Do that first. There should be vacuum at the end of that tiny hose with the engine running and the slider position on COLD. It’s is normally OPEN so it takes vacuum to close it which is provided by that plastic switch I posted and the slider on COLD.
I don’t recall which way you twist the adjuster but you’ll easily be able to see the end of the cable move when you turn it. You’ll have to remove the side console cover on the pass side to get to it. And the glove box to get to the top of the heater box.
Cable cam is not pushing button in on vacuum switch. I think we have something here🤨. Don’t know yet if I have a vacuum to the switch, I have to remove seat to remove side panel to get to adjustment. It’s may be light at the end of the tunnel. Will keep everyone advised and again appreciate all your help Larry
heat control leaver was in the COLD position during that picture Taken
Cable cam is not pushing button in on vacuum switch. I think we have something here🤨. Don’t know yet if I have a vacuum to the switch, I have to remove seat to remove side panel to get to adjustment. It’s may be light at the end of the tunnel. Will keep everyone advised and again appreciate all your help Larry
heat control leaver was in the COLD position during that picture Taken
YES!
If the slider lever is in the COLD position and your photo is the same the button is not being pushed in, thus no vacuum to the engine compartment Hot Water Shutoff valve...
Very Difficult to get in there to do that but I understand what you’re saying, maybe I’ll use a screwdriver tip to make up the difference between the cam and the pin so it’s completely in as far as it’ll go without damaging anything and give it a test to see if there is a vacuum going to the heater control valve. Thank you again.
” You the Man” I’ll let you know if we’re in business here
You're going to need to get in there regardless so go ahead and take the passenger seat out. It's easy. Remove the side console panel and find the adjuster cable. Turn the adjuster and you'll see the end that's attached to the switch move in and out. Adjust until the lever depresses the plunger then check the heater valve vacuum. Here's the cable adjuster.
great advice above! my only 2 cents.. adjust lever to .100- .200 " from the left bezel from full cold to insure you are pushing button..
i have factory vacuum shut off but also have shut off valves for summer as when you are driving and engine off the vacuum is lost and it does creep until restoring vacuum.. so basically the oem works great for 3 seasons
Eureka I have vacuum at the end of the vacuum line going to the heater control valve.
I use the long screwdriver too compress button in further than cam was pushing it in. I Started the engine and to my surprise vacuum vacuum vacuum.
Will tackle removing the seat and side panel as soon as the weather breaks down here.
i’m a happy camper. Thanks again to all of you who helped me i’ll let you know if everything works the way it should when I make the adjustment to the cable
Heater control valve operation
